amino acid analyses of antarctic cm2 meteorites using liquid … · 2010-02-12 · amino acid...

Meteoritics amp Planetary Science 41 Nr 6 889ndash902 (2006)Abstract available online at httpmeteoriticsorg

889 copy The Meteoritical Society 2006 Printed in USA

Amino acid analyses of Antarctic CM2 meteorites using liquid chromatographyndashtime of flightndashmass spectrometry

Daniel P GLAVIN1dagger Jason P DWORKIN1dagger Andrew AUBREY2 Oliver BOTTA1dagger James H DOTY III3dagger Zita MARTINS4 and Jeffrey L BADA2

1NASA Goddard Space Flight Center Greenbelt Maryland 20771 USA2Scripps Institution of Oceanography University of CaliforniamdashSan Diego San Diego California 92093ndash0212 USA

3Dematha Catholic High School Hyattsville Maryland 20781 USA4Leiden Institute of Chemistry 2300 RA Leiden The Netherlands

Corresponding author E-mail danielpglavinnasagov

(Received 30 November 2005 revision accepted 14 February 2006)

AbstractndashAmino acid analyses of the Antarctic CM2 chondrites Allan Hills (ALH) 83100 and LewisCliff (LEW) 90500 using liquid chromatographyndashtime of flightndashmass spectrometry (LC-ToF-MS)coupled with UV fluorescence detection revealed that these carbonaceous meteorites contain a suiteof indigenous amino acids not present in Antarctic ice Several amino acids were detected in ALH83100 including glycine alanine β-alanine γ-amino-n-butyric acid (γ-ABA) and α-aminoisobutyric acid (AIB) with concentrations ranging from 250 to 340 parts per billion (ppb) Incontrast to ALH 83100 the CM2 meteorites LEW 90500 and Murchison had a much higher totalabundance of these amino acids (440ndash3200 ppb) In addition ALH 83100 was found to have lowerabundances of the α-dialkyl amino acids AIB and isovaline than LEW 90500 and Murchison Thereare three possible explanations for the depleted amino acid content in ALH 83100 1) amino acidleaching from ALH 83100 during exposure to Antarctic ice meltwater 2) a higher degree of aqueousalteration on the ALH 83100 parent body or 3) ALH 83100 originated on a chemically distinct parentbody from the other two CM2 meteorites The high relative abundance of ε-amino-n-caproic acid(EACA) in the ALH 83100 meteorite as well as the Antarctic ice indicates that Nylon-6contamination from the Antarctic sample storage bags may have occurred during collection

INTRODUCTION

The investigation of organic compounds in primitivecarbonaceous chondrites provides a record of the chemicalprocesses that occurred in the early solar system In particularamino acids have been shown to be potential indicators intracing the nature of carbonaceous chondrite parent bodies(Ehrenfreund et al 2001) The delivery of amino acids bycarbonaceous chondrites to the early Earth could have alsobeen an important source of the Earthrsquos prebiotic organicinventory (Oroacute 1961 Anders 1989 Delsemme 1992 Chybaand Sagan 1992) The Murchison meteorite a non-AntarcticCM2 type carbonaceous chondrite that fell in Australia in1969 has been analyzed extensively for amino acids over thepast 35 years using a variety of techniques (Kvenvolden et al1970 Pereira et al 1975 Cronin et al 1979a Cronin andPizzarello 1983 Pizzarello et al 1994 Engel and Macko1997 Ehrenfreund et al 2001) Over 80 different amino acidshave been detected in the Murchison meteorite and they

comprise a mixture of C2 to C8 cyclic and acyclic monoaminoalkanoic and alkandioic acids of nearly complete structuraldiversity many of which are nonexistent in the terrestrialbiosphere (Cronin and Pizzarello 1983 Cronin and Chang1993 Botta and Bada 2002a Sephton 2002) The α-dialkylamino acids α-aminoisobutyric acid (AIB) and isovalinewhich are extremely rare amino acids on the Earth are two ofthe most abundant amino acids found in the Murchisonmeteorite (Kvenvolden et al 1971)

The subsequent discovery of a large number ofmeteorites in Antarctica since 1969 has provided additionalopportunities to search for organic compounds in CM typecarbonaceous chondrites Analyses of several Antarctic CM2carbonaceous meteorites have demonstrated that many ofthese samples contain a similar abundance and distribution ofamino acids compared to non-Antarctic CM2s such as theMurchison and Murray meteorites (Cronin and Moore 1971Kotra et al 1979 Shimoyama et al 1979 Cronin et al 1979aBotta and Bada 2002a) One exception is the Antarctic CM2

890 D P Glavin et al

meteorite Yamato (Y-) 791198 which contains the largesttotal abundance of AIB in any carbonaceous chondritestudied to date at approximately ten times the totalconcentration of AIB in Murchison (Shimoyama et al 1985Shimoyama and Ogasawara 2002) In contrast subsequentanalyses of the Y-793321 and Belgica (B-) 7904 meteoritesrevealed that these Antarctic CM2 meteorites were depletedin amino acids relative to other CM2s suggesting loss due toaqueous metamorphism on the parent body or leaching in theAntarctic ice (Shimoyama and Harada 1984) Although arelatively large sample size exists for the Antarctic CM2meteorites Allan Hills (ALH) 83100 and Lewis Cliff (LEW)90500 compared to other Antarctic CM2s these twometeorites have not been studied as extensively for aminoacids

The most common techniques that have been used foramino acid analyses of carbonaceous meteorites are reversephase high-performance liquid chromatography with UVfluorescence detection (HPLC-FD) and gas chromatography-mass spectrometry (GC-MS) Although these analyticaltechniques have been very useful for the characterization ofcomplex amino acid mixtures found in carbonaceousmeteorites (Kvenvolden et al 1970 Cronin et al 1982Ehrenfreund et al 2001 Glavin and Bada 2001) bothtechniques have their limitations For example HPLC-FD hasa much lower detection limit for amino acids (sim10minus14ndash10minus15

mol) than traditional GC-MS (sim10minus12 mol) detection butrelies on the identification of amino acids by fluorescenceretention time only (Lindroth and Mopper 1979 Cronin et al1979b Roach and Harmony 1987) Thereforemisidentification or inaccurate amino acid quantification byHPLC-FD due to the presence of interfering andor coelutingpeaks in meteorite extracts can occur With traditional GC-MS amino acids in meteorite extracts can be identified byboth retention time and by their characteristic massfragmentation pattern (Cronin and Pizzarello 1983)However the mass fragments of the parent ions generated byelectron impact (EI) ionization can often be difficult tointerpret when dealing with unknown compounds Inaddition there is reduced sensitivity in EI ionization GC-MScompared to other soft ionization liquid chromatography-mass spectrometry (LC-MS) techniques such as electrosprayionization (ESI) (eg Whitehouse et al 1985 Fenn et al1989) In ESI nitrogen gas is used to help nebulize the liquidfrom the HPLC and evaporate the solvent to impart a chargeon the analyte by the addition (ES+ mode M + H+) or removal(ESminus mode M minus H+) of a hydrogen ion with extremely lowfragmentation of the parent ion (M) The advantage of using atime of flight mass spectrometer (ToF-MS) over quadrupoleand ion trap mass spectrometers that are typically used in gaschromatography is that ToF-MS provides an exact molecularmass (RMS error le 3 ppm) that can be used to help determinethe molecular formula of an unknown parent compoundwithout significant mass fragmentation and the sensitivity is

not affected by coeluting compounds (Verentchikov et al1994 Krutchinsky et al 1998)

Recently the combination of HPLC-FD with ESI-MShas been used to analyze amino acids and amine standardsafter o-phthaldialdehydeN-acetyl-L-cysteine (OPANAC)derivatization (Kutlaacuten et al 2002 Mengerink et al 2002Hanczkoacute et al 2004 Gyimesi-Forraacutes et al 2005) For thisstudy we have for the first time combined traditional HPLC-FD with atmospheric ESI-ToF-MS for the identification ofOPANAC amino acid derivatives in meteorite extracts byfluorescence retention time and exact mass simultaneouslyHere we report on the first analyses of amino acids in theCM2 carbonaceous meteorites ALH 83100 LEW 90500 andMurchison using this new LC-ToF-MS analyticalconfiguration Amino acid analyses of any kind have notpreviously been reported for the ALH 83100 carbonaceousmeteorite

MATERIALS AND METHODS

Chemicals and Reagents

All of the chemicals used in this study were purchasedfrom Sigma-Aldrich and Fisher A stock amino acid solution(sim10minus5 M) was prepared by mixing individual standards (97ndash99 purity) in Millipore (182 MΩ) or double-distilled (dd)water The OPANAC reagent used for amino acidderivatization was prepared by dissolving 4 mg OPA in 300 microlmethanol (Fisher Optima) and then adding 685 microl 01 Msodium borate buffer (pH 9) and 15 microl 1 M NAC A 01 Mhydrazine (NH2NH2) solution was prepared by doublevacuum distillation of anhydrous hydrazine (98 purity) andsubsequent dilution in water The HCl was double-distilledand the ammonium formate buffer used in the LC-ToF-MSanalyses was prepared by NH4OH titration of a 50 mM formicacid solution to pH 8 A 5 microM phenolphthalein solution inacetonitrile with 01 formic acid was used for internal masscalibration of the ToF-MS

Samples

The Antarctic CM2 carbonaceous chondrites ALH 83100(split 246 parent 26 mass 56 g) and LEW 90500 (split 69parent 1 mass 50 g) analyzed in this study were interiorfragments selected by the meteorite sample curator at theNASA Johnson Space Center (JSC) These Antarcticmeteorite samples were collected during the 1983 and 1990Antarctic Search for Meteorites (ANSMET) field seasonsrespectively Several individual interior fragments (gt2 cmfrom fusion crust) of the CM2 meteorite Murchison (USNM66502 mass 63 g) that fell in southeastern Australia in 1969were provided by the Smithsonian National Museum ofNatural History A sample of crushed serpentine (a hydratedmagnesium silicate mineral present in these meteorite

Amino acid analyses of Antarctic CM2 meteorites 891

samples) that had been heated at 500 degC for 3 h was used as aprocedural blank In addition a 45 kg block of ice extractedfrom the La Paz region of Antarctica during the 2003ndash04ANSMET field season (La Paz 16704) was used as a controlfor the Antarctic meteorite analyses Antarctic ice samplesfrom the 1983 and 1990 field seasons in Allan Hills and LewisCliffs were not available for study (R Harvey personalcommunication) A sterile nylon bag of the type used to storethe Antarctic meteorite samples and ice after collection wasalso analyzed in parallel (provided by K Righter JSCmeteorite sample curator)

Extraction and Processing Procedures

All glassware and sample handling tools were rinsed withMillipore water wrapped in aluminum foil and then heated inan oven at 500 degC overnight The extraction protocol used inthis study was based on the extraction procedure used toisolate amino acids from the Murchison meteorite over 30years ago (Kvenvolden et al 1970) However in thisinvestigation we included an improved high temperature acidvapor hydrolysis procedure that was shown in previousstudies to be much faster and cleaner than the traditional acidliquid hydrolysis protocol (Tsugita et al 1987 Keil andKirchman 1991 Glavin et al 1999 Glavin and Bada 2001)

The meteorite sample vials were opened in a positivepressure (1 microm filtered air) clean room at the ScrippsInstitution of Oceanography (SIO) Individual meteoritefragments were then crushed using a mortar and pestle and aportion of the powdered samples transferred into clean pre-weighed glass test tubes (16 times 125 mm) and weighed againThe CM2 meteorites ALH 83100 (126 mg) LEW 90500(205 mg) and Murchison (140 mg) and the serpentine(253 mg) were flame-sealed inside individual test tubescontaining 1 ml of water and then heated for 24 h in a heatingblock set at 100 degC A small piece of nylon was cut from thetop of the Antarctic meteorite storage bag (47 mg) transferredto a test tube and then carried through the identical hot waterextraction procedure as the meteorites In addition the samenylon bag was extracted in water at room temperature byadding 5 ml of water directly to the interior of the bag After24 h the water was removed from the nylon bag andprocessed in the same manner as the meteorite samplesdescribed below

After hot water extraction the tubes were rinsed with ddwater to remove exterior surface contamination broken openand then centrifuged for 5 min to separate sample particulatefrom the water supernatant One half of the water supernatantfrom each tube was transferred to a new test tube (10 times75 mm) dried under vacuum and then hydrolyzed under 6 MHCl vapor by flame-sealing each small test tube inside alarger test tube (20 times 150 mm) containing 1 ml dd 6 M HCland then by placing the large sealed tubes in an oven at 150 degCfor 3 h The remaining water supernatants were not acid-

hydrolyzed in order to determine the concentration of freeamino acids in the extracts After vapor hydrolysis the largetubes were broken open and the small interior tubes removedand dried under vacuum to remove any residual HCl from thehydrolyzed sample Both the hydrolyzed and unhydrolyzedresidues were redissolved in 3 ml water and desalted via acation exchange column (AG 50W-X8 100ndash200 meshhydrogen form BIO-RAD) The nylon bag water extractswere not desalted During column loading a DL-norleucineinternal standard was added to each sample to estimate theamino acid recoveries from desalting and derivatizationNorleucine was selected since this amino acid had a very lateHPLC retention time and did not interfere with most of themeteoritic amino acids of interest After elution of the anionicspecies with water the amino acids were obtained by elutionwith 3 ml aqueous 2 M NH4OH The NH4OH eluate was driedunder vacuum resuspended in 20 microl 01 M sodium boratebuffer (pH 9) and derivatized with 5 microl OPANAC (Zhao andBada 1995) in glass vials The derivatization reaction wasthen quenched after 1 or 15 minutes at room temperature with75 microl of 50 mM sodium acetate buffer (SIO) or 75 microl of 01 Mhydrazine hydrate (NASA Goddard Space Flight Center[GSFC]) and the solution was loaded into the auto samplercarousel at 4 degC prior to HPLC-FD and LC-ToF-MS analysis(GSFC)

The sim45 kg block of Antarctic ice (La Paz 16704) wasremoved from the nylon sample bag wrapped with cleanaluminum foil that had been heated at 500 degC overnight andthen rinsed with dd water in order to remove surfacecontaminants (the washing procedure removed approximately10 of the total ice by volume) A previous analysis of AllanHills Antarctic ice at SIO has shown that significant aminoacid contamination from both nitrile and latex gloves canoccur from direct exposure of the ice block to the glovesduring the rinsing procedure (unpublished data from SIO)Therefore direct contact with the La Paz Antarctic ice sampleusing nitrile or latex gloves was avoided The La Paz icesample was melted overnight in a large glass beaker that hadbeen heated at 500 degC overnight and the top of the beaker wascovered with aluminum foil The following day 4 microl of themelted ice water was concentrated using rotary evaporation at45ndash50 degC and the dried residue dissolved in dd water (100 microl)One tenth of the unfiltered ice extract was derivatized withOPANAC and then analyzed using HPLC-FD andLC-ToF-MS (GSFC) A blank consisting of one liter dd waterwas carried through the identical rotovap processingprocedure as the Antarctic ice

HPLC-FD and LC-ToF-MS Detection

Amino acid derivatives and their enantiomeric ratios inthe meteorite and ice samples were independently analyzedafter derivatization by reverse phase HPLC-FD at SIO and atGSFC For the HPLC-FD measurements at SIO amino acids


were eluted from a Phenomenex Synergi 4 microm Hydro-reversephase column (46 times 250 mm) at 1 mlmin with a binarygradient of 50 mM sodium acetate buffer (8 methanol pH55) and methanol and then detected using a Shimadzu RF-530 fluorescence detector (λex = 340 nm and λem = 450 nm)At GSFC the HPLC-FD measurements were made with aWaters Alliance 2695 HPLC system controlled by MassLynx40 coupled to a 2475 multi-λ fluorescence detector at thesame excitation and emission wavelengths as SIO Aminoacid separation was achieved with a Phenomenex Luna 5 micromreverse phase phenyl-hexyl column (46 mm times 250 mm) andmaintained at 30 degC elution was performed using a ternarygradient with 50 mM ammonium formate buffer (8methanol pH 8) and increasing amounts of water andmethanol at a flow rate of 1 mlmin (Fig 1)

In addition to UV fluorescence detection theunfragmented masses of the amino acid OPANACderivatives that eluted from the column were detected byorthogonal acceleration reflectron time of flight massspectrometry using a Waters LCT Premier ToF-MS

instrument at GSFC The mass spectrometer was run in ldquoWoptics moderdquo which employs three reflectrons to provide aFWHM mass resolution of greater than 8000 in themonitored mass range of 100ndash1000 mz For all runs thecolumn eluant (flow rate 1 mlmin) was split 85 to the FDand 15 to the ToF-MS The ToF-MS was configured forESI with a 1 s integration time in each ionization mode andalternated between ES+ and ESminus every 02 s during theacquisition The ESI settings were desolvation gas (N2)temperature 250 degC 600 lh capillary voltage 38 kV (ES+)and 42 kV (ESminus) cone voltage 20 V (ES+) and 35 V (ESminus)The instrument was optimized for maximum sensitivity ofOPANAC amino acid derivatives in the 300ndash450 mzrange with detection limits in the subfemtomole (sim10ndash15 to10ndash16 mol) range

Mass calibration of the ToF-MS during the acquisitionwas maintained by monitoring a reference compound(phenolphthalein C20H14O4 monoisotopic mass (M) =3180892 Da 5 microM in acetonitrile and 01 formic acid)every 10 s which was delivered to the MS via a separate pump

Fig 1 The 0ndash35 min region of the HPLC-FD and LC-ToF-MS chromatograms obtained from a single injection of a mixture of OPANAClabeled (15 min derivatization) amino acid standards (sim10 pmol of each compound) Amino acid peak identifications are given in Table 1 TheUV fluorescence trace is shown at the bottom and the exact mass traces were obtained simultaneously in positive electrospray mode for theindividual amino acid standards A detection limit for these amino acids using both UV fluorescence and ToF-MS was determined to be about10minus15ndash10minus16 mol (SN sim30) The conditions for amino acid separations for the mobile phase at 30 degC were as follows flow rate 1 mlminsolvent A (water) solvent B (methanol) solvent C (50 mM ammonium formate 8 methanol pH 80) gradient 0ndash5 min 100 C 5ndash15 min0ndash83 A and 0ndash12 B 15ndash22 min 83ndash75 A and 12ndash20 B 22ndash35 min 75ndash35 A and 20ndash60 B Peaks 1ndash6 were magnified tenfolddue to suppression of the ionization efficiency under highly aqueous conditions during this stage of the HPLC gradient The asterisks in the36710 mz mass trace correspond to OPANAC labeled aminobutyric acids (peaks 10 11 13ndash16) with two naturally occurring 13C atoms Asimilar figure was obtained from negative electrospray mode (data not shown)


at 10 microlmin to an independent and alternating ESI sprayerThis allows the exact mass of OPANAC amino acidderivatives to be determined within plusmn 0001 Da (sim3 ppm)Under these conditions the sensitivity for ToF-MS detectionof the OPANAC amino acid derivatives was higher in ES+mode compared to ESminus mode therefore the 12C monoisotopicmass of the protonated OPANAC-amino acid molecular ionwas used for quantification Peak areas were obtained byperforming two 4 channel Savitzky-Golay smoothing of thespectrum and then plotting a chromatogram of a given mass atFWHM (typically 7ndash9 channels or about plusmn 002 Da around thecenter of the peak) No significant difference in area wasfound by a twofold alteration of the smoothing parametersThe peaks generated in this chromatogram were manuallyintegrated in MassLynx

RESULTS AND DISCUSSION

The amino acid data from this study are based on theHPLC-FD and LC-ToF-MS techniques described aboveAmino acid peak identifications for all chromatograms aregiven in Table 1 A sample chromatogram demonstratingHPLC separation and detection of a standard mixture ofamino acids by both UV fluorescence and exact mass usingthe LC-ToF-MS instrument at GSFC is shown in Fig 1 Theamino acid concentrations for the CM2 carbonaceousmeteorites and Antarctic ice are the average of multipleindependent analyses of the same extracts at SIO and atGSFC Each peak in the chromatograms was identified bycomparison of its UV fluorescence retention time and exactmolecular mass with those of authentic amino acid referencestandards

Amino Acid Analyses of the CM2 CarbonaceousMeteorites

The HPLC-FD chromatograms of the 6 M HCl-hydrolyzed hot water extracts from the GSFC analyses of theCM2 meteorites ALH 83100 LEW 90500 and Murchison andthe serpentine blank are shown in Fig 2 Similar HPLC-FD

chromatograms for these meteorites were obtained by SIO(data not shown) Simultaneous LC-ToF-MS mass data inboth ES+ and ESminus modes were also collected for thesemeteorites at GSFC The relative distributions of amino acidsin the Murchison and LEW 90500 chromatograms werefound to be similar but not identical (Fig 3) which isconsistent with previous analyses of these two meteorites(Ehrenfreund et al 2001 Botta and Bada 2002b) The mostabundant amino acids detected in Murchison and LEW 90500were α-aminoisobutyric acid (AIB) and isovaline (1300 to3200 ppb) with lower levels of aspartic and glutamic acidsglycine β-alanine α-ABA β-ABA γ-ABA and valine(Table 2) The α-dialkyl amino acids AIB and isovaline areextremely rare on Earth and thus characteristic of aminoacids of apparent extraterrestrial origin The amino acid serinewas also identified in the Murchison and LEW 90500 acid-hydrolyzed hot-water extracts by HPLC-FD at SIO but thisamino acid was not detected by HPLC-FD or LC-ToF-MSanalyses at GSFC (Fig 2) therefore only an upper limit forserine is reported in Table 2 It should be emphasized thatthere are other unknown amino acid and primary amine peakspresent in the HPLC-FD chromatograms of these meteoriteextracts that were not identified by comparison with knownstandards (Fig 2) for this study

The chromatographic separation of γ-ABA from β-AIBby HPLC was not achieved under the conditions used atGSFC In addition since γ-ABA and β-AIB have identicalmolecular masses we were unable to differentiate betweenthese two amino acids using LC-ToF-MS therefore the totalconcentration of these amino acids is reported as a sum inTable 2 β-AIB has previously been reported to be present atlower concentrations (sim150ndash340 ppb) compared to γ-ABA(sim720ndash1330 ppb) in the CM2 meteorites Murchison andMurray (Ehrenfreund et al 2001) Trace amounts (lt10 ppb)of L-aspartic acid L-serine glycine β-alanine L-alanine andL-valine in the serpentine blank could be detected by standardHPLC-FD and LC-ToF-MS (Fig 2) which indicates that onlyvery low levels of amino acid contamination of the samplesoccurred during the processing procedure However the lowabundance of amino acids in the serpentine blank does not

Table 1 Peak identifications and abbreviations for amino acids detected in the standard and meteorite samplesPeak Amino acid Peak Amino acid

1 D-aspartic acid 13 D-β-amino-n-butyric acid (D-β-ABA)2 L-aspartic acid 14 α-aminoisobutyric acid (AIB)3 L-glutamic acid 15 L-β-amino-n-butyric acid (L-β-ABA)4 D-glutamic acid 16 DL-α-amino-n-butyric acid (DL-α-ABA)5 D-serine 17 D-isovaline6 L-serine 18 L-isovaline7 Glycine 19 L-valine8 β-alanine 20 X ε-amino-n-caproic acid (EACA)9 D-alanine 21 D-valine10 γ-amino-n-butyric acid (γ-ABA) 22 D-isoleucine11 DL-β-aminoisobutyric acid (DL-β-AIB) 23 L-isoleucine12 L-alanine 24 DL-leucine


rule out the possibility of amino acid contamination of themeteorites during collection storage or handling of thesamples

Although the distribution of amino acids in Murchisonand LEW 90500 is similar the total concentration of aminoacids in the acid-hydrolyzed hot-water extract of Murchisonis sim14600 ppb compared to sim9000 ppb for LEW 90500(Table 2) These total amino acid concentrations should beconsidered lower limits since not all of the amino acidspresent in these meteorite extracts were identified andquantified A similar set of free amino acids was also detectedin the unhydrolyzed water extracts of Murchison and LEW90500 (Table 2) From the data in Table 2 we calculate thatthe ratio of free amino acids to total amino acids (free +bound) in Murchison (045 plusmn 008) is identical to the ratio inLEW 90500 (043 plusmn 013) The low free to total amino acidratio in ALH 83100 (008 plusmn 002) compared to Murchison andLEW 90500 is due to a high concentration of peptide boundldquocompound Xrdquo in ALH 83100 (detailed discussion ofcompound X in later section)

The large increase in amino acid concentration in bothMurchison and LEW 90500 after acid hydrolysis indicatesthat amino acids in these meteorites occur as both free amino

acids and as derivatives andor acid labile precursors that canbe converted to amino acids after acid hydrolysis (Cronin1976a) However it has been reported that acid labileprecursors including amino acid dipeptides anddiketopiperazines (cyclic dimers of amino acids) account foronly a small percentage (005ndash20) of the acid-liberatedamino acids in Murchison (Cronin 1976b Shimoyama andOgasawara 2002) and that most of the precursors inMurchison are low molecular weight amino acid derivativesincluding mono- and dicarboxylic acid amides hydroxy acidamides lactams carboxylactams lactims N-acetylaminoacids and substituted hydantoins (Cronin 1976a Cooper andCronin 1995) Analyses of these linear and cyclic aliphaticamides in the LEW 90500 and ALH 83100 meteorites havenot been reported

The DL enantiomeric ratios calculated for several aminoacids in Murchison LEW 90500 and ALH 83100 are reportedin Table 3 Since racemic mixtures of amino acids (DL sim1)are predicted for reactions (eg Strecker-cyanohydrinsynthesis) believed to be active on CM2 meteorite parentbodies (Peltzer et al 1984 Lerner et al 1993 Ehrenfreundet al 2001) the relatively high DL ratios (08ndash10) measuredfor the protein amino acids aspartic acid glutamic acid and

Fig 2 The 0ndash32 min region (only the norleucine internal standard peak appeared outside of this region) of the HPLC-FD chromatograms fromthe GSFC analyses Similar chromatograms were obtained from SIO and are available upon request OPANAC derivatization (15 min) ofamino acids in the 6M HCl-hydrolyzed hot-water extracts from the CM2 carbonaceous chondrite Murchison the Antarctic CM2 meteoritesLEW 90500 and ALH 83100 and the serpentine blank The peaks were identified by comparison of the retention time and exact molecularmass to those in the amino acid standard run on the same day All of the coeluting amino acids were separated and quantified by their exactmasses with the exception of peak numbers 10 + 11 which correspond to γ-ABA and DL-β-AIB (mass data for ALH 83100 shown in Figs 4and 6)


alanine and the nonprotein amino acid β-ABA in the CM2meteorites Murchison and LEW 90500 (Table 3) suggeststhat a large fraction of these amino acids are indigenous inorigin Analyses of the Murchison meteorite less than twoyears after its fall to Earth revealed that several protein aminoacids including alanine glutamic acid valine proline and thenon-protein amino acids ABA β-AIB and norvaline werenearly racemic (DL sim1) with minimal terrestrialcontamination (Kvenvolden et al 1970 1971) Racemicmixtures of protein and nonprotein amino acids have alsobeen detected in the Antarctic CM2 chondrites Y-74662 andY-791198 (Shimoyama et al 1979 Shimoyama andOgasawara 2002) The calculated DL ratios for the aminoacids in ALH 83100 ranged from 07 for aspartic acid to 10for β-ABA (Table 3) Terrestrial L-amino acid contaminationof these meteorites after their fall to Earth especially forvaline (DL sim05 for Murchison and LEW 90500 Table 3)may have lowered the initial DL ratios of these protein aminoacids to the DL ratios presently observed Previous analysesof Murchison have also shown that L-enantiomeric excessesof the nonprotein amino acid isovaline range from 0ndash152with significant variation between meteorite fragments(Pizzarello and Cronin 2000 Pizzarello et al 2003) Sinceisovaline is an extremely rare amino acid on Earth thecontribution of terrestrial contamination to the L-isovalineexcess observed in Murchison is unlikely (Pizzarello andCronin 2000) The enantiomeric ratios for isovaline detectedin Murchison and LEW 90500 are not reported here but arediscussed elsewhere (Glavin and Dworkin 2006)

Amino Acid Depletion in ALH 83100

In contrast to Murchison and LEW 90500 the ALH83100 meteorite contained much lower abundances of mostamino acids with total concentrations ranging from lt1 to338 ppb (Table 2) One notable difference was the lowrelative and total abundances of AIB (250 ppb) and isovaline(lt10 ppb) in ALH 83100 compared to Murchison and LEW90500 (Table 2 Fig 3) One possible explanation for thedepleted amino acid content of ALH 83100 relative to otherCM2 meteorites is a loss of water-extractable amino acids dueto ice meltwater exposure in Antarctica The Antarctic CM2carbonaceous chondrites Y-793321 and B-7904 were alsofound to be depleted in amino acids relative to other AntarcticCM2 meteorites (Shimoyama and Harada 1984) Given aresidence time in the Antarctic ice of 116 ka for ALH 83100(Jull et al 1998) it is possible that some fraction of theoriginal amino acids were leached from the meteorite duringthis time Experiments designed to study the leaching ofamino acids from the Murchison carbonaceous chondrite afterexposure of the meteorite to cold water (4 degC) indicate thatabout half of the free amino acids including AIB and isovalinecould be leached from the meteorite after only 6 weeks whilethe remaining more strongly bound amino acids wereextracted only after heating the meteorite in hot water(100 degC) for 24 h (Kminek et al 2002) Since the terrestrialresidence time of LEW 90500 has not been reported it isdifficult to draw any correlation between Antarctic meteoriteexposure time and amino acid leaching at this time

Fig 3 A comparison of the relative molar amino acid abundances (glycine = 10) of alanine (stripes) β-alanine (white) α-aminoisobutyricacid (black) and isovaline (gray) in the acid-hydrolyzed hot-water extracts of several carbonaceous chondrites The relative amino acidabundances for the CM2 meteorites Murchison LEW 90500 and ALH 83100 are from this study only The data for the Y-791198 and Orgueilmeteorites were calculated from previous analyses (Shimoyama and Ogasawara 2002 Ehrenfreund et al 2001)

896 D P Glavin et alTa

ble

2 S

umm

ary

of th

e av

erag

e bl

ank-

corr

ecte

d am

ino

acid

con

cent

ratio

ns in

the

unhy

drol

yzed

(fre

e) a

nd H

Cl a

cid

hydr

olyz

ed (t

otal

) hot

-wat

er e

xtra

cts

of

the

CM

2 ty

pe c

arbo

nace

ous

met

eorit

es M

urch

ison

LEW

905

00 a

nd A

LH 8

3100

and

an

unhy

drol

yzed

Ant

arct

ic ic

e ex

tract

as

mea

sure

d by

two

sepa

rate

an

alys

es o

ne a

t SIO

and

the

othe

r at G

SFC

a A

min

o ac

id d

etec

ted

CM

2 ca

rbon

aceo

us m

eteo

rites

Ant

arct

ic ic

eM

urch

ison

LEW

905

00A

LH 8

3100

La P

az 1

6704

Fre

e (p

pb)

Tota

l (p

pb)

Fre

e (p

pb)

Tota

l (p

pb)

Free

(p

pb)

Tota

l (p

pb)

Free

(p

pt)

D-a

spar

tic a

cid

18 plusmn

212

0 plusmn

1615

plusmn 3

127

plusmn 24

7 plusmn

229

plusmn 4

lt0

3L-

aspa

rtic

acid

23 plusmn

313

2 plusmn

1523

plusmn 5

151

plusmn 73

10 plusmn

343

plusmn 6

13

plusmn 0

3D

-glu

tam

ic a

cid

10 plusmn

434

3 plusmn

449

plusmn 3

317

plusmn 55

2 plusmn

121

plusmn 7

lt0

1L-

glut

amic

aci

d26

plusmn 2

357

plusmn 42

22 plusmn

431

6 plusmn

554

plusmn 2

23 plusmn

6 lt

01

D-s

erin

e lt

4lt1

38b

lt8lt2

19b

lt4lt4

03

plusmn 0

2L-

serin

e lt

5lt1

73b

lt14

lt235

blt5

lt5

37

plusmn 0

1G

lyci

ne34

5 plusmn

2719

95 plusmn

122

520

plusmn 32

1448

plusmn 6

8211

7 plusmn

1230

0 plusmn

759

6 plusmn

24

β-al

anin

e30

2 plusmn

1814

19 plusmn

157

161

plusmn 21

442

plusmn 23

810

4 plusmn

833

8 plusmn

310

2 plusmn

01

γ-am

ino-

n-bu

tyric

aci

d +

DL

-β-A

IBc

437

plusmn 30

1460

plusmn 2

1313

2 plusmn

1216

4 plusmn

2115

5 plusmn

2530

8 plusmn

68 lt

01

D-a

lani

ne16

2 plusmn

1062

3 plusmn

619

8 plusmn

1034

3 plusmn

171

38 plusmn

611

0 plusmn

440

5 plusmn

01

L-al

anin

e17

1 plusmn

865

9 plusmn

8420

3 plusmn

935

2 plusmn

161

43 plusmn

813

4 plusmn

192

5 plusmn

08

D-β

-am

ino-

n-bu

tyric

aci

d91

plusmn 6

233

plusmn17

61 plusmn

715

5 plusmn

1619

plusmn 4

33 plusmn

8 lt

01

L-β-

amin

o-n-

buty

ric a

cid

93 plusmn

11

256

plusmn 15

62 plusmn

717

2 plusmn

4027

plusmn 5

33 plusmn

12

lt0

1α

-am

inoi

sobu

tyric

aci

d (A

IB)

2349

plusmn 4

0431

82 plusmn

620

1364

plusmn 1

8827

06 plusmn

377

115

plusmn 27

250

plusmn 40

46 plusmn

5D

L-α

-am

ino-

n-bu

tyric

aci

dc28

4 plusmn

9540

3 plusmn

156

243

plusmn 98

431

plusmn 15

911

plusmn 4

19 plusmn

5 lt

01

DL

-isov

alin

e18

72 plusmn

48

2796

plusmn 2

9862

5 plusmn

2113

06 plusmn

83

lt5

lt10

lt0

1ε-

amin

o-n-

capr

oic

acid

(EA

CA

)d26

4 plusmn

138

268

plusmn 12

322

8 plusmn

161

386

plusmn 16

914

6 plusmn

6084

80 plusmn

953

886

plusmn 11

8D

-val

ine

37 plusmn

210

3 plusmn

921

plusmn 2

48 plusmn

12

lt1

lt1

lt0

1L-

valin

e73

plusmn 9

218

plusmn 23

46 plusmn

10

102

plusmn 16

lt1

lt1

lt0

1To

tal

6600

146

0039

0090

0080

010

100

950

a The

val

ues

are

repo

rted

in p

arts

per

bill

ion

(ppb

) for

the

met

eorit

es a

nd p

arts

per

trill

ion

(ppt

) for

the

Ant

arct

ic ic

e on

a b

ulk

sam

ple

basi

s Q

uant

ifica

tion

of th

e am

ino

acid

s in

clud

ed b

ackg

roun

d le

vel

corr

ectio

n us

ing

a se

rpen

tine

blan

k an

d a

com

paris

on o

f the

pea

k ar

eas

with

thos

e of

an

amin

o ac

id s

tand

ard

The

fina

l val

ues

wer

e no

rmal

ized

usi

ng th

e de

salti

ng a

nd d

eriv

atiz

atio

n re

cove

ries

of a

nin

tern

al D

L-n

orle

ucin

e st

anda

rd (r

ecov

erie

s ra

nged

from

60ndash

75

for t

he m

eteo

rite

sam

ples

) Th

e un

certa

intie

s (δ

x) a

re b

ased

on

the

stan

dard

dev

iatio

n of

the

aver

age

valu

e of

bet

wee

n th

ree

and

six

sepa

rate

mea

sure

men

ts (N

) with

a s

tand

ard

erro

r δ

x =

σx sdot

(N minus

1)minus 1

2 F

or a

ll U

V fl

uore

scen

ce d

ata

co-

elut

ing

amin

o ac

id p

eaks

and

or c

ompo

unds

with

inte

rfer

ing

peak

s w

ere

not i

nclu

ded

in th

eav

erag

eb T

hese

val

ues m

ust b

e co

nsid

ered

upp

er li

mits

sinc

e th

ey w

ere

dete

cted

at S

IO b

ut w

ere

not d

etec

ted

at G

SFC

c A

min

o ac

ids a

ndo

r ena

ntio

mer

s cou

ld n

ot b

e se

para

ted

unde

r the

chr

omat

ogra

phic

con

ditio

ns u

sed

d Maj

or c

ompo

nent

of N

ylon

-6 id

entif

ied

as p

eak

X in

met

eorit

e an

d ic

e sa

mpl

es a

lso

know

n as

6-a

min

ohex

anoi

c ac

id


Another possibility for the depleted amino acid levels inALH 83100 is aqueous alteration on the meteorite parentbody Shimoyama and Harada (1984) have previouslysuggested that low temperature andor aqueousmetamorphism on the parent bodies of Y-793321 andBelgica-7904 could have been responsible for the amino aciddepletion observed in these meteorites relative to other lessaltered Antarctic CM2 meteorites Analyses of Mg-richphyllosilicates and Ca-Mg carbonates in ALH 83100 suggestthat this Antarctic CM2 meteorite has been extensivelyaltered by parent body processes (Zolensky and Browning1994) Therefore it is possible that ALH 83100 originated ona parent body that was depleted in amino acids andor theirprecursors because of more thorough aqueous processing Incontrast to ALH 83100 examination of the fine-grainedmineralogy of Y-791198 indicate that this Antarctic meteoritemay be the most weakly altered CM meteorite analyzed todate (Chizmadia and Brearley 2003) A comparison of therelative amino acid abundances in the CM2 meteorites Y-791198 Murchison LEW 90500 ALH 83100 and the moreextensively altered CI1 carbonaceous meteorite Orgueil(Zolensky and McSween 1988) may indicate some trends inamino acid distribution with respect to the degree of parentbody alteration (Fig 3) In general the relative abundance ofβ-alanine relative to glycine appears to be higher inmeteorites that have experienced more extensive aqueousalteration such as the CM2 ALH 83100 and the CI1 Orgueilwhile the relative abundance of AIB in these meteorites islower than in the other less altered CM2 meteorites Howeverthe relative abundance ratios in these meteorites should beinterpreted with caution since these amino acid ratios werenot corrected for the potential contribution of terrestrialglycine contamination which could vary between meteoritesamples Additional studies of more CM meteorites may helpreveal whether or not the relative distribution of amino acidsin carbonaceous chondrites is influenced by the degree ofaqueous alteration on the parent body

It is also possible that ALH 83100 originated on a parentbody that was chemically distinct from the other CM2meteorites The absolute and relative abundances of the α-dialkyl amino acids AIB and isovaline are lower in ALH83100 than in other CM2 meteorites including MurchisonLEW 90500 and Y-791198 (Fig 3) If Strecker-cyanohydrinsynthesis was the predominant pathway for the formation ofα-amino acids on these CM2 meteorite parent bodies (Peltzeret al 1984 Ehrenfreund et al 2001) then the parent body ofALH 83100 may have been depleted in acetone and 2-butanone required for the formation of AIB and isovaline bythe Strecker pathway However alternative sources for aminoacids in carbonaceous meteorites have also been proposed(Bernstein et al 2002) For example β-amino acids cannot beproduced by the Strecker-cyanohydrin pathway but must beformed by a different synthetic pathway than α-amino acidsIt has previously been suggested that the synthesis of β-alanine in carbonaceous meteorites could proceed by Michael

addition of ammonia to cyanoacetylene followed byhydrolysis (Miller 1957 Cronin and Chang 1993Ehrenfreund et al 2001)

Identification of Compound X in ALH 83100

The most striking difference between ALH 83100 andthe other CM2s was the large unidentified compound (labeledpeak lsquoXrsquo in Fig 2) present in the acid hydrolyzed hot waterextract of ALH 83100 at a much higher concentration (8480ppb) than detected in the Murchison (268 ppb) and LEW90500 (386 ppb) meteorite extracts (Table 2) Peak X wasonly detected at a very low concentration (146 ppb) in thewater extract of ALH 83100 prior to acid hydrolysis whichindicated that compound X was present in predominantlybound or peptide form In a previous investigation of theAntarctic martian meteorites ALH 84001 and MIL 03346 anunidentified compound with a similar retention time as peakX was also observed in the acid hydrolyzed water extractshowever the mass of the peak could not determined under theanalytical conditions used (Bada et al 1998 Glavin et al2005)

Since the abundance of peak X in the ALH 83100 extractwas much higher than in previous analyses of Antarcticmeteorites we were able to measure the mass of the OPANAC derivative of the unknown compound (Mx + H+ =393148) by LC-ToF-MS (Figs 4 and 6) Although theretention time of peak X is identical to L-valine under ourchromatographic conditions peak X cannot be L-valinewhich has a different mass Mval + H+ = 379133 (Figs 1 and2) The mass of peak X was identical to leucine isoleucineand the norleucine internal standard that are routinely testedhowever the retention time of peak X was substantiallydifferent from these amino acid standards (Fig 4) SinceOPANAC only reacts with primary amines to form afluorescent derivative compound X must contain a primaryamine group with a molecular weight identical to ournorleucine internal standard We determined that the area of

Table 3 Amino acid enantiomeric ratios in the CM2 carbonaceous meteorites

Amino acid Enantiomeric ratio (DL)a

Murchison LEW 90500 ALH 83100

Aspartic acid 091 084 067Glutamic acid 096 100 091Alanine 095 097 082Valine 048 047 bdcβ-amino-n-butyric acidb

091 090 100

Isovalineb ndd ndd bdcaDL ratios calculated from the total concentrations reported in Table 2

The uncertainties ranged from plusmn 005 to plusmn 02 and are based on theabsolute errors shown in Table 2

bNonprotein amino acidcbd = below detectiondnd = not determined


peak X was lower after 15 min versus 1 min OPANACreaction times This indicates that compound X unlike AIBand isovaline does not contain two alkyl groups in the α-position to the amine (Zhao and Bada 1995) Furthermore wehave observed that the same decrease in peak area after 15min OPANAC derivatization compared to a 1 minderivatization that we see with peak X will occur with aminoacids when a CH2 group is in the α-position to the aminogroup (eg glycine β-alanine γ-ABA) This decrease in peakintensity with OPANAC derivatization time has previouslybeen observed with amino acids containing a minusCH2-NH2moiety and is due to the reaction of the initially formed OPANAC derivative with one additional OPA molecule(Mengerink et al 2002 Hanczkoacute et al 2004) Among themost plausible compounds for peak X was the straightchained C6 amino acid 6-aminohexanoic acid or ε-amino-n-caproic acid (EACA) We determined that the retention timeof EACA was consistent with compound X and we verifiedthat it is compound X by co-injection of the ALH 83100extract with an equal concentration of authentic EACA

Analysis of the La Paz Antarctic Ice Sample

LC-ToF-MS analysis of the La Paz Antarctic ice samplerevealed trace levels of aspartic acid serine glycine

β-alanine and alanine above procedural blank levels withfree concentrations ranging from 02 to sim10 parts per trillion(ppt) in the unfiltered ice extract (Table 2) These levels area factor of sim104 lower than those observed in the Antarcticmeteorite samples (Table 2) Moreover several amino acidsthat were detected in the Antarctic CM2 meteorites LEW90500 and ALH 83100 including glutamic acid α-ABAβ-ABA γ-ABA isovaline and valine were not detected inthe ice above the 01 ppt level A similar distribution ofamino acids was also detected in a previous HPLC-FDanalysis of ice collected from the Allan Hills region ofAntarctica (Bada et al 1998) Therefore it is highly unlikelythat the Antarctic ice is the source of the majority of aminoacids detected in the Antarctic CM2 meteorites ALH 83100and LEW 90500

Perhaps one of the most intriguing findings in the La Paz16704 Antarctic ice sample is the relatively large amount ofAIB (46 ppt) present in the extract (Table 2) Theidentification of AIB in the ice sample was confirmed usingHPLC-FD and LC-ToF-MS by comparison of thefluorescence retention time and exact mass to an authenticAIB standard Moreover a large increase of the peak in the LaPaz ice sample was observed after a 15 min OPANACderivatization of the ice extract as compared to a 1 minderivatization This provided additional evidence for the

Fig 4 The 0ndash32 min region of the HPLC-FD and ToF-MS chromatograms of the ALH 83100 meteorite acid hydrolyzed water extract Thepeaks were identified by comparison of the retention time and exact molecular mass to those in the amino acid standard run on the same dayAspartic and glutamic acids (peaks 1ndash3) could not be identified by exact mass due to a low abundance and poor ionization of these compoundsduring the analysis


presence of AIB since the reaction of the α-dialkyl aminoacid AIB with the OPANAC reagent requires longer to reachcompletion (Zhao and Bada 1995) AIB was not detected in asample of Antarctic ice from the Allan Hills region above the2 ppt level (Bada et al 1998) which suggests that thedistribution of AIB in Antarctic ice is heterogeneous

Since AIB has now been identified in several AntarcticCM2 chondrites (Cronin et al 1979a Kotra et al 1979Shimoyama et al 1985 Botta and Bada 2002a this study) andalso in Antarctic carbonaceous micrometeorites (Brinton et al1998 Matrajt et al 2004) it is possible that AIB may haveleached from carbonaceous meteorites present in the ice(Kminek et al 2001) However there were no carbonaceousmeteorites found in the vicinity of the La Paz ice sample 16704at the time of collection Although the source of the AIB in theLa Paz ice could not be determined from this study onepossible explanation could be Antarctic micrometeorites(AMMs) present in the ice It has been well established thatmicrometeorites represent the main source of extraterrestrialmaterial accreted by the Earth each year (Chyba and Sagan1992 Love and Brownlee 1993) Although most AMMs do notcontain AIB (Glavin et al 2004) even a small amount of AIBderived from micrometeorites present in the ice would havebeen concentrated during the melting and roto-evaporationprocessing procedures The La Paz 16704 ice water extract wasnot filtered to isolate micrometeorites prior to LC-ToF-MSanalysis so this hypothesis cannot be confirmed

Nylon Contamination of the Antarctic Meteorite and IceSamples

The most abundant amino acid present in the La Paz16704 ice water extract was EACA With an EACAconcentration of 886 ppt this amino acid accounted for 93of the total mass of identified free amino acids present in theice (Table 2) Since this ice sample was sealed in a nylon bagat the time of collection it is likely that the EACA detected inthe ice sample is derived from the nylon material

To test this hypothesis a nylon bag of the type used tostore Antarctic meteorite samples was carried through themeteorite extraction procedure We found that EACA was themost abundant water extractable amino acid constituent of thenylon storage bag with a total concentration of sim23000 partsper million (ppm) after hot water (100 degC) extraction and acidhydrolysis A much lower concentration of the free EACAmonomer was detected by LC-ToF-MS in the unhydrolyzedfraction (sim13 ppm) which indicates that the dominant waterextractable form of EACA is a peptide of Nylon-6 Using

LC-ToF-MS we were able to identify peptides in theunhydrolyzed nylon water extract up to the EACA heptamerM + 2H+ = 536330 (data not shown) A high yield of EACAwas also obtained from water extracts of the nylon bag kept atroom temperature These results are not surprising sinceNylon-6 is a peptide of EACA (Fig 5) Acid hydrolysis ofNylon-6 will therefore yield large quantities of free EACAOnly trace levels of other amino acids including glycine β-alanine γ-ABA and alanine were detected in the nylon bagacid-hydrolyzed water extract (sim01ndash03 ppm)

The identification of EACA by retention time and exactmass in the ALH 83100 meteorite the Antarctic ice and nylonbag extracts using LC-ToF-MS (Figs 4 and 6) demonstratesthat this compound is a potential amino acid contaminant forall Antarctic meteorite samples or ice collected using nylonstorage bags Given the extremely high water extractableconcentration of EACA in Nylon-6 and the fact thatAntarctic meteorites are sometimes covered with ice or snowwhen sealed inside the nylon storage bags in the field it is notsurprising that a high concentration of EACA (8480 ppb) wasdetected in ALH 83100 Assuming EACA was derivedentirely from nylon nylon contamination in ALH 83100accounts for roughly 85 of the total abundance of aminoacids in the meteorite (Table 2)

In contrast to ALH 83100 a much lower concentration ofthe EACA was detected in LEW 90500 (386 ppb) whichindicates that the extent of EACA contamination from nylonin Antarctic meteorites may be highly variable It is possiblethat the LEW 90500 meteorite sample contained only limitedexterior snow or ice when collected in Antarctica or theinterior fragment of LEW 90500 that we analyzed was lesssusceptible to nylon contamination than exterior pieces TheMurchison meteorite sample which was stored in low densitypolyethylene (LDPE) bags at the Smithsonian NationalMuseum of Natural History (L Welzenbach personalcommunication) contained the lowest abundance of EACA(268 ppb) of the meteorite samples analyzed (Table 2) Inaddition the ratios of free to total EACA in Murchison (10)and LEW 90500 (06) are much higher compared to ALH83100 (002) providing additional evidence that most of theEACA in Murchison and LEW 90500 is not derived fromNylon-6 but is instead indigenous to these meteorites as hasbeen found for other C6 amino acids in Murchison (Croninet al 1981) It is also worth noting that only very low levels(sim210 ppb) of predominantly free EACA (freetotal = 08)were reported in the Y-91198 Antarctic meteorite sample thatwas collected and stored in a Teflon bag (Shimoyama andOgasawara 2002)

Fig 5 Nylon-6 is a polymer (peptide) of ε-amino-n-caproic acid (EACA) which readily hydrolyzes to the monomer


CONCLUSIONS

In this study we have demonstrated that liquidchromatographyndashtime of flightndashmass spectrometry (LC-ToF-MS) can be a useful tool for the identification of amino acidsin meteorite and ice samples LC-ToF-MS coupled withHPLC-FD fluorescence detection is a very powerfulcombination with a detection limit for amino acids that is atleast three orders of magnitude lower than traditional gaschromatography-mass spectrometry (GC-MS) techniquesUsing this new analytical technique we were able to identifya total of 20 different amino acids and their enantiomers in theAntarctic CM2 meteorites ALH 83100 and LEW 90500 aswell as the non-Antarctic CM2 meteorite Murchison Manymore amino acids were observed in Murchison and LEW90500 but have not yet been identified using this techniqueThe high DL amino acid ratios in these samples as well as thepresence of a variety of structural isomers for C3 to C5 aminoacids suggest that most of the amino acids are indigenous tothese meteorites ALH 83100 was depleted in amino acidswith a strikingly different amino acid distribution comparedto the CM2 meteorites LEW 90500 and Murchison Wecannot rule out the possibility that some amino acids wereleached from the ALH 83100 meteorite during its residencetime in the Antarctic ice The unique distribution of aminoacids in ALH 83100 may indicate that this meteoriteoriginated from a chemically distinct parent body from the

CM2 meteorites Murchison and LEW 90500 andor the ALH83100 parent body was depleted in amino acid precursormaterial due to a higher degree of aqueous alteration

One amino acid that has previously been detected in theAntarctic Martian meteorites ALH 84001 and MIL 03346 buthas eluded identification was also detected in ALH 83100and determined by LC-ToF-MS to be ε-amino-n-caproic acid(EACA) EACA is a likely amino acid contaminant derivedfrom the nylon bag used to store the Antarctic meteoritesamples Fortunately Nylon-6 leaches only trace levels ofother amino acids however future meteorite collection effortsin Antarctica should consider other types of sterile samplestorage bags such as Teflon or LDPE as an alternative toNylon-6 Finally due to the coelution of EACA with L-valineunder most HPLC separation schemes researchers should becareful to avoid misidentification using this technique

AcknowledgmentsndashThe authors would like to thank KRighter the meteorite sample curator at NASA JohnsonSpace Center for providing the Antarctic CM2 meteoritesand nylon storage bag used in this study T McCoy and LWelzenbach who kindly allocated the Murchison meteoritesample the 2003-04 ANSMET field team for help in thecollection of the Antarctic ice sample from La Paz We arealso grateful to R Harvey T Jull M Bernstein and ananonymous reviewer for helpful comments We appreciatefunding support from the NASA Astrobiology Institute and

Fig 6 a) Single ion LC-ToF-MS trace at mz 39315 in ES+ mode of compound X in the ALH 83100 meteorite La Paz Antarctic ice sampleand nylon bag water extracts b) Peak X was identified as ε-amino-n-caproic acid (EACA) based on the exact mass and retention time of theOPANAC derivative in both ES+ and ESminus modes In addition peaks corresponding to the OPANAC labeled EACA compound containingone two and three naturally occurring 13C atoms were also detected in these extracts


the Goddard Center for Astrobiology the NASA SpecializedCenter of Research and Training in Exobiology at UCSD andfrom Fundaccedilatildeo para a Ciecircncia e a Tecnologia (scholarshipSFRHBD105182002) at the Leiden Institute of Chemistry

Editorial HandlingmdashDr A J Timothy Jull

REFERENCES

Anders E 1989 Pre-biotic organic matter from comets and asteroidsNature 342255ndash257

Bada J L Glavin D P McDonald G D and Becker L 1998 Asearch for amino acids in Martian meteorite ALH 84001 Science279362ndash365

Bernstein M P Dworkin J P Cooper G W Sandford S A andAllamandola L J 2002 Racemic amino acids from theultraviolet photolysis of interstellar ice analogues Nature 416401ndash403

Botta O and Bada J L 2002a Extraterrestrial organic compounds inmeteorites Surveys in Geophysics 23411ndash467

Botta O and Bada J L 2002b Amino acids in the Antarctic CMmeteorite LEW 90500 (abstract 1391) 33rd Lunar andPlanetary Science Conference CD-ROM

Brinton K L F Engrand C Glavin D P Bada J L and MauretteM 1998 A search for extraterrestrial amino acids incarbonaceous Antarctic micrometeorites Origins of Life andEvolution of the Biosphere 28413ndash424

Chizmadia L and Brearley A J 2003 Mineralogy and texturalcharacteristics of fine-grained rims in the Yamato-791198 CM2carbonaceous chondrite Constraints on the location of aqueousalteration (abstract 1419) 34th Lunar and Planetary ScienceConference CD-ROM

Chyba C and Sagan C 1992 Endogenous production exogenousdelivery and impact-shock synthesis of organic molecules Aninventory for the origins of life Nature 355125ndash132

Cooper G W and Cronin J R 1995 Linear and cyclic aliphaticcarboxamides of the Murchison meteorite-hydrolyzablederivatives of amino-acids and other carboxylic acidsGeochimica et Cosmochimica Acta 591003ndash1015

Cronin J R 1976a Acid-labile amino acid precursors in theMurchison meteorite I Chromatographic fractionation Originsof Life and Evolution of the Biosphere 7337ndash342

Cronin J R 1976b Acid-labile amino acid precursors in theMurchison meteorite II A search for peptides and amino acylamides Origins of Life and Evolution of the Biosphere 7343ndash348

Cronin J R and Moore C B 1971 Amino acid analyses of theMurchison Murray and Allende carbonaceous chondritesScience 1721327ndash1329

Cronin J R and Pizzarello S 1983 Amino acids in meteoritesAdvances in Space Research 35ndash18

Cronin J R and Chang S 1993 Organic matter in meteoritesMolecular and isotopic analyses of the Murchison meteorite InThe chemistry of lifersquos origin edited by Greenberg J MMendoza-Gomez C X and Pirronello V Dordrecht TheNetherlands Kluwer pp 209ndash258

Cronin J R Pizzarello S and Moore C B 1979a Amino acids inan Antarctic carbonaceous chondrite Science 206335ndash337

Cronin J R Gandy W E and Pizzarello S 1979b Amino acidanalysis with o-pthaldialdehyde detection Effects of reactiontemperature and thiol on fluorescence yields AnalyticalBiochemistry 93174ndash179

Cronin J R Gandy W E and Pizzarello S 1981 Amino acids of the

Murchison meteorite I Six carbon acyclic primary alpha-aminoalkanoic acids Journal of Molecular Evolution 17265ndash272

Cronin J R Yuen G U and Pizzarello S 1982 Gaschromatographic-mass spectral analysis of the five-carbon β- γ-and δ-amino alkanoic acids Analytical Biochemistry 124139ndash149

Delsemme A H 1992 Cometary origin of carbon nitrogen andwater on the Earth Origins of Life and Evolution of the Biosphere21279ndash298

Ehrenfreund P Glavin D P Botta O Cooper G and Bada J L2001 Extraterrestrial amino acids in Orgueil and Ivuna Tracingthe parent body of CI type carbonaceous chondrites Proceedingsof the National Academy of Sciences 982138ndash2141

Engel M and Macko S 1997 Isotopic evidence for extraterrestrialnon-racemic amino-acids in the Murchison meteorite Nature389265ndash268

Fenn J B Mann M Meng C K Wong S F and Whitehouse C M1989 Electrospray ionization for mass spectrometry of largebiomolecules Science 24664ndash71

Glavin D P Bada J L Brinton K L F and McDonald G D 1999Amino acids in the Martian meteorite Nakhla Proceedings of theNational Academy of Sciences 968835ndash8838

Glavin D P and Bada J L 2001 Survival of amino acids inmicrometeorites during atmospheric entry Astrobiology 1259ndash269

Glavin D P and Dworkin J P 2006 Investigation of isovalineenantiomeric excesses in CM meteorites using liquidchromatography time-of-flight mass spectrometry (abstract)Astrobiology 6105

Glavin D P Matrajt G and Bada J L 2004 Re-examination ofamino acids in Antarctic micrometeorites Advances in SpaceResearch 33106ndash113

Glavin D P Aubrey A Dworkin J P Botta O and Bada J L 2005Amino acids in the Antarctic Martian meteorite MIL 03346(abstract 1920) 32nd Lunar and Planetary Science ConferenceCD-ROM

Gyimesi-Forraacutes K Leitner A Akasaka K and Lindner W 2005Comparative study on the use of ortho-phthaldialdehydenaphthalene-23-dicarboxaldehyde and anthracene-23-dicarboxaldehyde reagents for α-amino acids followed by theenantiomer separation of the formed isoindolin-1-one derivativesusing quinine-type chiral stationary phases Journal ofChromatography A 108380ndash88

Hanczkoacute R Kutlaacuten D Toacuteth F and Molnaacuter-Perl I 2004 Behaviorand characteristics of the o-pthaldialdehyde derivatives of n-C6-C8 amines and phenylethylamines with four additive SH-containing reagents Journal of Chromatography A 103151ndash66

Jull A J T Cloudt S and Cielaszyk E 1998 14C terrestrial ages ofmeteorites from Victoria Land Antarctica and the infall rate ofmeteorites In Meteorites Flux with time and impact effectsedited by McCall G J Hutchison R Grady M M and RotheryD London The Geological Society pp 75ndash91

Keil R G and Kirchman D L 1991 Dissolved combined amino-acids in marine waters as determined by a vapor-phase hydrolysismethod Marine Chemistry 33243ndash259

Kminek G Botta O Glavin D P and Bada J L 2002 Amino acidsin the Tagish Lake meteorite Meteoritics amp Planetary Science37697ndash701

Kotra R K Shimoyama A Ponnamperuma C and Hare P E 1979Amino acids in a carbonaceous chondrite from AntarcticaJournal of Molecular Evolution 13179ndash183

Krutchinsky A N Chernushevich I V Spicer V L Ens W andStanding K G 1998 Collisional damping interface for anelectrospray ionization time-of-flight mass spectrometer Journalof the American Society for Mass Spectrometry 9569ndash579


Kutlaacuten D Presits P and Molnaacuter-Perl I 2002 Behavior andcharacteristics of amine derivatives obtained with o-phthaldialdehyde3-mercaptopropionic acid and with o-pthaldialdehydeN-acetyl-L-cysteine reagents Journal ofChromatography A 949235ndash248

Kvenvolden K A Lawless J Pering K Peterson E Flores JPonnamperuma C Kaplan I and Moore C 1970 Evidence forextraterrestrial amino acids and hydrocarbons in the Murchisonmeteorite Nature 228923ndash926

Kvenvolden K A Lawless J G Ponnomperuma C 1971 Non-protein amino acids in the Murchison meteorite Proceedings ofthe National Academy of Sciences 68486ndash490

Lerner N R Peterson E and Chang S 1993 The Strecker synthesisas a source of amino-acids in carbonaceous chondrites deuteriumretention during synthesis Geochimica et Cosmochimica Acta574713ndash4723

Lindroth P and Mopper K 1979 High performance liquidchromatographic determination of subpicomole amounts ofamino acids by precolumn fluorescence derivatization with o-pthaldialdehyde Analytical Chemistry 511667ndash1674

Love S G and Brownlee D E 1993 A direct measurement of theterrestrial mass accretion rate of cosmic dust Science 262550ndash553

Matrajt G Pizzarello S Taylor S and Brownlee D E 2004Concentration and variability of the AIB amino acid in polarmicrometeorites Implications for the exogenous delivery ofamino acids to the primitive Earth Meteoritics amp PlanetaryScience 391849ndash1858

Mengerink Y Kutlaacuten D Toacuteth F Csaacutempai A and Molnaacuter-Perl I2002 Advances in the evaluation of the stability andcharacteristics of the amino acid and amine derivatives obtainedwith the o-phthaldialdehyde3-mercaptopropionic acid and o-phthaldialdehydeN-acetyl-L-cysteine reagents High-performance liquid chromatography-mass spectrometry studyJournal of Chromatography A 94999ndash124

Miller S L 1957 The mechanism of synthesis of amino acids byelectric discharges Biochimica et Biophysica Acta 23480ndash489

Oroacute J 1961 Comets and the formation of biochemical compounds onthe primitive Earth Nature 190389ndash390

Peltzer E T Bada J L Schlesinger G and Miller S L 1984 Thechemical conditions on the parent body of the Murchisonmeteorite Some conclusions based on amino hydroxy anddicarboxylic acids Advances in Space Research 469ndash74

Pereira W E Summons R E Rindfleisch T C Duffield A MZeitman B and Lawless J G 1975 Stable isotope massfragmentographymdashIdentification and hydrogen-deuteriumexchange studies of eight Murchison meteorite amino acidsGeochimica et Cosmochimica Acta 39163ndash172

Pizzarello S and Cronin J R 2000 Non-racemic amino acids in theMurray and Murchison meteorites Geochimica etCosmochimica Acta 64329ndash338

Pizzarello S Feng X Epstein S and Cronin J R 1994 Isotopicanalyses of nitrogenous compounds from the Murchisonmeteorite Ammonia amines amino acids and polarhydrocarbons Geochimica et Cosmochimica Acta 585579ndash5587

Pizzarello S Zolensky M and Turk K A 2003 Nonracemicisovaline in the Murchison meteorite Chiral distribution andmineral association Geochimica et Cosmochimica Acta 671589ndash1595

Roach M C and Harmony M D 1987 Determination of aminoacids at subfemtomole levels by high-performance liquidchromatography with laser-induced fluorescence detectionAnalytical Chemistry 59411ndash415

Sephton M 2002 Organic compounds in meteorites NaturalProduct Reports 19292ndash311

Shimoyama A and Harada K 1984 Amino acid depletedcarbonaceous chondrites (C2) from Antarctica GeochemicalJournal 18281ndash286

Shimoyama A and Ogasawara R 2002 Dipeptides anddiketopiperazines in the Yamato-791198 and Murchisoncarbonaceous chondrites Origins of Life and Evolution of theBiosphere 32165ndash179

Shimoyama A Ponnamperuma C and Yanai K 1979 Amino acidsin the Yamato carbonaceous chondrite from Antarctica Nature282394ndash396

Shimoyama A Harada K and Yanai K 1985 Amino-acids from theYamato-791198 carbonaceous chondrite from AntarcticaChemistry Letters 81183ndash1186

Tsugita A Uchida T Mewes H W and Ataka T 1987 A rapidvapor-phase acid (hydrochloric-acid and trifluoroacetic-acid)hydrolysis of peptide and protein Journal of Biochemistry 1021593ndash1597

Verentchikov A N Ens W and Standing K G 1994 Reflectingtime-of-flight mass spectrometer with an electrospray ion sourceand orthogonal extraction Analytical Chemistry 66126ndash133

Van Eijk H M H Rooyakkers D R Soeters P B and Deutz N EP 1999 Determination of amino acid isotope enrichment usingliquid chromatography-mass spectrometry Analytical Chemistry2718ndash17

Whitehouse C M Dreyer R N Yamashita M and Fenn J B 1985Electrospray interface for liquid chromatographs and massspectrometers Analytical Chemistry 57675ndash679

Zhao M and Bada J L 1995 Determination of -dialkyl amino acidsand their enantiomers in geological samples by HPLC afterderivatization with a chiral adduct of o-phthaldialdehydeJournal of Chromatography A 69055ndash63

Zolensky M E and Browning L B 1994 CM chondrites exhibit thecomplete petrologic range from type 2 to 1 Meteoritics 29556

Zolensky M E and McSween H Y Jr 1988 In Meteorites and theearly solar system edited by Kerridge J F and Matthews M STucson Arizona The University of Arizona Press pp 114ndash143


meteorite Yamato (Y-) 791198 which contains the largesttotal abundance of AIB in any carbonaceous chondritestudied to date at approximately ten times the totalconcentration of AIB in Murchison (Shimoyama et al 1985Shimoyama and Ogasawara 2002) In contrast subsequentanalyses of the Y-793321 and Belgica (B-) 7904 meteoritesrevealed that these Antarctic CM2 meteorites were depletedin amino acids relative to other CM2s suggesting loss due toaqueous metamorphism on the parent body or leaching in theAntarctic ice (Shimoyama and Harada 1984) Although arelatively large sample size exists for the Antarctic CM2meteorites Allan Hills (ALH) 83100 and Lewis Cliff (LEW)90500 compared to other Antarctic CM2s these twometeorites have not been studied as extensively for aminoacids

The most common techniques that have been used foramino acid analyses of carbonaceous meteorites are reversephase high-performance liquid chromatography with UVfluorescence detection (HPLC-FD) and gas chromatography-mass spectrometry (GC-MS) Although these analyticaltechniques have been very useful for the characterization ofcomplex amino acid mixtures found in carbonaceousmeteorites (Kvenvolden et al 1970 Cronin et al 1982Ehrenfreund et al 2001 Glavin and Bada 2001) bothtechniques have their limitations For example HPLC-FD hasa much lower detection limit for amino acids (sim10minus14ndash10minus15

mol) than traditional GC-MS (sim10minus12 mol) detection butrelies on the identification of amino acids by fluorescenceretention time only (Lindroth and Mopper 1979 Cronin et al1979b Roach and Harmony 1987) Thereforemisidentification or inaccurate amino acid quantification byHPLC-FD due to the presence of interfering andor coelutingpeaks in meteorite extracts can occur With traditional GC-MS amino acids in meteorite extracts can be identified byboth retention time and by their characteristic massfragmentation pattern (Cronin and Pizzarello 1983)However the mass fragments of the parent ions generated byelectron impact (EI) ionization can often be difficult tointerpret when dealing with unknown compounds Inaddition there is reduced sensitivity in EI ionization GC-MScompared to other soft ionization liquid chromatography-mass spectrometry (LC-MS) techniques such as electrosprayionization (ESI) (eg Whitehouse et al 1985 Fenn et al1989) In ESI nitrogen gas is used to help nebulize the liquidfrom the HPLC and evaporate the solvent to impart a chargeon the analyte by the addition (ES+ mode M + H+) or removal(ESminus mode M minus H+) of a hydrogen ion with extremely lowfragmentation of the parent ion (M) The advantage of using atime of flight mass spectrometer (ToF-MS) over quadrupoleand ion trap mass spectrometers that are typically used in gaschromatography is that ToF-MS provides an exact molecularmass (RMS error le 3 ppm) that can be used to help determinethe molecular formula of an unknown parent compoundwithout significant mass fragmentation and the sensitivity is

not affected by coeluting compounds (Verentchikov et al1994 Krutchinsky et al 1998)

Recently the combination of HPLC-FD with ESI-MShas been used to analyze amino acids and amine standardsafter o-phthaldialdehydeN-acetyl-L-cysteine (OPANAC)derivatization (Kutlaacuten et al 2002 Mengerink et al 2002Hanczkoacute et al 2004 Gyimesi-Forraacutes et al 2005) For thisstudy we have for the first time combined traditional HPLC-FD with atmospheric ESI-ToF-MS for the identification ofOPANAC amino acid derivatives in meteorite extracts byfluorescence retention time and exact mass simultaneouslyHere we report on the first analyses of amino acids in theCM2 carbonaceous meteorites ALH 83100 LEW 90500 andMurchison using this new LC-ToF-MS analyticalconfiguration Amino acid analyses of any kind have notpreviously been reported for the ALH 83100 carbonaceousmeteorite

MATERIALS AND METHODS

Chemicals and Reagents

All of the chemicals used in this study were purchasedfrom Sigma-Aldrich and Fisher A stock amino acid solution(sim10minus5 M) was prepared by mixing individual standards (97ndash99 purity) in Millipore (182 MΩ) or double-distilled (dd)water The OPANAC reagent used for amino acidderivatization was prepared by dissolving 4 mg OPA in 300 microlmethanol (Fisher Optima) and then adding 685 microl 01 Msodium borate buffer (pH 9) and 15 microl 1 M NAC A 01 Mhydrazine (NH2NH2) solution was prepared by doublevacuum distillation of anhydrous hydrazine (98 purity) andsubsequent dilution in water The HCl was double-distilledand the ammonium formate buffer used in the LC-ToF-MSanalyses was prepared by NH4OH titration of a 50 mM formicacid solution to pH 8 A 5 microM phenolphthalein solution inacetonitrile with 01 formic acid was used for internal masscalibration of the ToF-MS

Samples

The Antarctic CM2 carbonaceous chondrites ALH 83100(split 246 parent 26 mass 56 g) and LEW 90500 (split 69parent 1 mass 50 g) analyzed in this study were interiorfragments selected by the meteorite sample curator at theNASA Johnson Space Center (JSC) These Antarcticmeteorite samples were collected during the 1983 and 1990Antarctic Search for Meteorites (ANSMET) field seasonsrespectively Several individual interior fragments (gt2 cmfrom fusion crust) of the CM2 meteorite Murchison (USNM66502 mass 63 g) that fell in southeastern Australia in 1969were provided by the Smithsonian National Museum ofNatural History A sample of crushed serpentine (a hydratedmagnesium silicate mineral present in these meteorite








































ble

2 S

umm

ary

of th

e av

erag

e bl

ank-

corr

ecte

d am

ino

acid

con

cent

ratio

ns in

the

unhy

drol

yzed

(fre

e) a

nd H

Cl a

cid

hydr

olyz

ed (t

otal

) hot

-wat

er e

xtra

cts

of

the

CM

2 ty

pe c

arbo

nace

ous

met

eorit

es M

urch

ison

LEW

905

00 a

nd A

LH 8

3100

and

an

unhy

drol

yzed

Ant

arct

ic ic

e ex

tract

as

mea

sure

d by

two

sepa

rate

an

alys

es o

ne a

t SIO

and

the

othe

r at G

SFC

a A

min

o ac

id d

etec

ted

CM

2 ca

rbon

aceo

us m

eteo

rites

Ant

arct

ic ic

eM

urch

ison

LEW

905

00A

LH 8

3100

La P

az 1

6704

Fre

e (p

pb)

Tota

l (p

pb)

Fre

e (p

pb)

Tota

l (p

pb)

Free

(p

pb)

Tota

l (p

pb)

Free

(p

pt)

D-a

spar

tic a

cid

18 plusmn

212

0 plusmn

1615

plusmn 3

127

plusmn 24

7 plusmn

229

plusmn 4

lt0

3L-

aspa

rtic

acid

23 plusmn

313

2 plusmn

1523

plusmn 5

151

plusmn 73

10 plusmn

343

plusmn 6

13

plusmn 0

3D

-glu

tam

ic a

cid

10 plusmn

434

3 plusmn

449

plusmn 3

317

plusmn 55

2 plusmn

121

plusmn 7

lt0

1L-

glut

amic

aci

d26

plusmn 2

357

plusmn 42

22 plusmn

431

6 plusmn

554

plusmn 2

23 plusmn

6 lt

01

D-s

erin

e lt

4lt1

38b

lt8lt2

19b

lt4lt4

03

plusmn 0

2L-

serin

e lt

5lt1

73b

lt14

lt235

blt5

lt5

37

plusmn 0

1G

lyci

ne34

5 plusmn

2719

95 plusmn

122

520

plusmn 32

1448

plusmn 6

8211

7 plusmn

1230

0 plusmn

759

6 plusmn

24

β-al

anin

e30

2 plusmn

1814

19 plusmn

157

161

plusmn 21

442

plusmn 23

810

4 plusmn

833

8 plusmn

310

2 plusmn

01

γ-am

ino-

n-bu

tyric

aci

d +

DL

-β-A

IBc

437

plusmn 30

1460

plusmn 2

1313

2 plusmn

1216

4 plusmn

2115

5 plusmn

2530

8 plusmn

68 lt

01

D-a

lani

ne16

2 plusmn

1062

3 plusmn

619

8 plusmn

1034

3 plusmn

171

38 plusmn

611

0 plusmn

440

5 plusmn

01

L-al

anin

e17

1 plusmn

865

9 plusmn

8420

3 plusmn

935

2 plusmn

161

43 plusmn

813

4 plusmn

192

5 plusmn

08

D-β

-am

ino-

n-bu

tyric

aci

d91

plusmn 6

233

plusmn17

61 plusmn

715

5 plusmn

1619

plusmn 4

33 plusmn

8 lt

01

L-β-

amin

o-n-

buty

ric a

cid

93 plusmn

11

256

plusmn 15

62 plusmn

717

2 plusmn

4027

plusmn 5

33 plusmn

12

lt0

1α

-am

inoi

sobu

tyric

aci

d (A

IB)

2349

plusmn 4

0431

82 plusmn

620

1364

plusmn 1

8827

06 plusmn

377

115

plusmn 27

250

plusmn 40

46 plusmn

5D

L-α

-am

ino-

n-bu

tyric

aci

dc28

4 plusmn

9540

3 plusmn

156

243

plusmn 98

431

plusmn 15

911

plusmn 4

19 plusmn

5 lt

01

DL

-isov

alin

e18

72 plusmn

48

2796

plusmn 2

9862

5 plusmn

2113

06 plusmn

83

lt5

lt10

lt0

1ε-

amin

o-n-

capr

oic

acid

(EA

CA

)d26

4 plusmn

138

268

plusmn 12

322

8 plusmn

161

386

plusmn 16

914

6 plusmn

6084

80 plusmn

953

886

plusmn 11

8D

-val

ine

37 plusmn

210

3 plusmn

921

plusmn 2

48 plusmn

12

lt1

lt1

lt0

1L-

valin

e73

plusmn 9

218

plusmn 23

46 plusmn

10

102

plusmn 16

lt1

lt1

lt0

1To

tal

6600

146

0039

0090

0080

010

100

950

a The

val

ues

are

repo

rted

in p

arts

per

bill

ion

(ppb

) for

the

met

eorit

es a

nd p

arts

per

trill

ion

(ppt

) for

the

Ant

arct

ic ic

e on

a b

ulk

sam

ple

basi

s Q

uant

ifica

tion

of th

e am

ino

acid

s in

clud

ed b

ackg

roun

d le

vel

corr

ectio

n us

ing

a se

rpen

tine

blan

k an

d a

com

paris

on o

f the

pea

k ar

eas

with

thos

e of

an

amin

o ac

id s

tand

ard

The

fina

l val

ues

wer

e no

rmal

ized

usi

ng th

e de

salti

ng a

nd d

eriv

atiz

atio

n re

cove

ries

of a

nin

tern

al D

L-n

orle

ucin

e st

anda

rd (r

ecov

erie

s ra

nged

from

60ndash

75

for t

he m

eteo

rite

sam

ples

) Th

e un

certa

intie

s (δ

x) a

re b

ased

on

the

stan

dard

dev

iatio

n of

the

aver

age

valu

e of

bet

wee

n th

ree

and

six

sepa

rate

mea

sure

men

ts (N

) with

a s

tand

ard

erro

r δ

x =

σx sdot

(N minus

1)minus 1

2 F

or a

ll U

V fl

uore

scen

ce d

ata

co-

elut

ing

amin

o ac

id p

eaks

and

or c

ompo

unds

with

inte

rfer

ing

peak

s w

ere

not i

nclu

ded

in th

eav

erag

eb T

hese

val

ues m

ust b

e co

nsid

ered

upp

er li

mits

sinc

e th

ey w

ere

dete

cted

at S

IO b

ut w

ere

not d

etec

ted

at G

SFC

c A

min

o ac

ids a

ndo

r ena

ntio

mer

s cou

ld n

ot b

e se

para

ted

unde

r the

chr

omat

ogra

phic

con

ditio

ns u

sed

d Maj

or c

ompo

nent

of N

ylon

-6 id

entif

ied

as p

eak

X in

met

eorit

e an

d ic

e sa

mpl

es a

lso

know

n as

6-a

min

ohex

anoi

c ac

id












091 090 100






















CONCLUSIONS









REFERENCES








































































































ble

2 S

umm

ary

of th

e av

erag

e bl

ank-

corr

ecte

d am

ino

acid

con

cent

ratio

ns in

the

unhy

drol

yzed

(fre

e) a

nd H

Cl a

cid

hydr

olyz

ed (t

otal

) hot

-wat

er e

xtra

cts

of

the

CM

2 ty

pe c

arbo

nace

ous

met

eorit

es M

urch

ison

LEW

905

00 a

nd A

LH 8

3100

and

an

unhy

drol

yzed

Ant

arct

ic ic

e ex

tract

as

mea

sure

d by

two

sepa

rate

an

alys

es o

ne a

t SIO

and

the

othe

r at G

SFC

a A

min

o ac

id d

etec

ted

CM

2 ca

rbon

aceo

us m

eteo

rites

Ant

arct

ic ic

eM

urch

ison

LEW

905

00A

LH 8

3100

La P

az 1

6704

Fre

e (p

pb)

Tota

l (p

pb)

Fre

e (p

pb)

Tota

l (p

pb)

Free

(p

pb)

Tota

l (p

pb)

Free

(p

pt)

D-a

spar

tic a

cid

18 plusmn

212

0 plusmn

1615

plusmn 3

127

plusmn 24

7 plusmn

229

plusmn 4

lt0

3L-

aspa

rtic

acid

23 plusmn

313

2 plusmn

1523

plusmn 5

151

plusmn 73

10 plusmn

343

plusmn 6

13

plusmn 0

3D

-glu

tam

ic a

cid

10 plusmn

434

3 plusmn

449

plusmn 3

317

plusmn 55

2 plusmn

121

plusmn 7

lt0

1L-

glut

amic

aci

d26

plusmn 2

357

plusmn 42

22 plusmn

431

6 plusmn

554

plusmn 2

23 plusmn

6 lt

01

D-s

erin

e lt

4lt1

38b

lt8lt2

19b

lt4lt4

03

plusmn 0

2L-

serin

e lt

5lt1

73b

lt14

lt235

blt5

lt5

37

plusmn 0

1G

lyci

ne34

5 plusmn

2719

95 plusmn

122

520

plusmn 32

1448

plusmn 6

8211

7 plusmn

1230

0 plusmn

759

6 plusmn

24

β-al

anin

e30

2 plusmn

1814

19 plusmn

157

161

plusmn 21

442

plusmn 23

810

4 plusmn

833

8 plusmn

310

2 plusmn

01

γ-am

ino-

n-bu

tyric

aci

d +

DL

-β-A

IBc

437

plusmn 30

1460

plusmn 2

1313

2 plusmn

1216

4 plusmn

2115

5 plusmn

2530

8 plusmn

68 lt

01

D-a

lani

ne16

2 plusmn

1062

3 plusmn

619

8 plusmn

1034

3 plusmn

171

38 plusmn

611

0 plusmn

440

5 plusmn

01

L-al

anin

e17

1 plusmn

865

9 plusmn

8420

3 plusmn

935

2 plusmn

161

43 plusmn

813

4 plusmn

192

5 plusmn

08

D-β

-am

ino-

n-bu

tyric

aci

d91

plusmn 6

233

plusmn17

61 plusmn

715

5 plusmn

1619

plusmn 4

33 plusmn

8 lt

01

L-β-

amin

o-n-

buty

ric a

cid

93 plusmn

11

256

plusmn 15

62 plusmn

717

2 plusmn

4027

plusmn 5

33 plusmn

12

lt0

1α

-am

inoi

sobu

tyric

aci

d (A

IB)

2349

plusmn 4

0431

82 plusmn

620

1364

plusmn 1

8827

06 plusmn

377

115

plusmn 27

250

plusmn 40

46 plusmn

5D

L-α

-am

ino-

n-bu

tyric

aci

dc28

4 plusmn

9540

3 plusmn

156

243

plusmn 98

431

plusmn 15

911

plusmn 4

19 plusmn

5 lt

01

DL

-isov

alin

e18

72 plusmn

48

2796

plusmn 2

9862

5 plusmn

2113

06 plusmn

83

lt5

lt10

lt0

1ε-

amin

o-n-

capr

oic

acid

(EA

CA

)d26

4 plusmn

138

268

plusmn 12

322

8 plusmn

161

386

plusmn 16

914

6 plusmn

6084

80 plusmn

953

886

plusmn 11

8D

-val

ine

37 plusmn

210

3 plusmn

921

plusmn 2

48 plusmn

12

lt1

lt1

lt0

1L-

valin

e73

plusmn 9

218

plusmn 23

46 plusmn

10

102

plusmn 16

lt1

lt1

lt0

1To

tal

6600

146

0039

0090

0080

010

100

950

a The

val

ues

are

repo

rted

in p

arts

per

bill

ion

(ppb

) for

the

met

eorit

es a

nd p

arts

per

trill

ion

(ppt

) for

the

Ant

arct

ic ic

e on

a b

ulk

sam

ple

basi

s Q

uant

ifica

tion

of th

e am

ino

acid

s in

clud

ed b

ackg

roun

d le

vel

corr

ectio

n us

ing

a se

rpen

tine

blan

k an

d a

com

paris

on o

f the

pea

k ar

eas

with

thos

e of

an

amin

o ac

id s

tand

ard

The

fina

l val

ues

wer

e no

rmal

ized

usi

ng th

e de

salti

ng a

nd d

eriv

atiz

atio

n re

cove

ries

of a

nin

tern

al D

L-n

orle

ucin

e st

anda

rd (r

ecov

erie

s ra

nged

from

60ndash

75

for t

he m

eteo

rite

sam

ples

) Th

e un

certa

intie

s (δ

x) a

re b

ased

on

the

stan

dard

dev

iatio

n of

the

aver

age

valu

e of

bet

wee

n th

ree

and

six

sepa

rate

mea

sure

men

ts (N

) with

a s

tand

ard

erro

r δ

x =

σx sdot

(N minus

1)minus 1

2 F

or a

ll U

V fl

uore

scen

ce d

ata

co-

elut

ing

amin

o ac

id p

eaks

and

or c

ompo

unds

with

inte

rfer

ing

peak

s w

ere

not i

nclu

ded

in th

eav

erag

eb T

hese

val

ues m

ust b

e co

nsid

ered

upp

er li

mits

sinc

e th

ey w

ere

dete

cted

at S

IO b

ut w

ere

not d

etec

ted

at G

SFC

c A

min

o ac

ids a

ndo

r ena

ntio

mer

s cou

ld n

ot b

e se

para

ted

unde

r the

chr

omat

ogra

phic

con

ditio

ns u

sed

d Maj

or c

ompo

nent

of N

ylon

-6 id

entif

ied

as p

eak

X in

met

eorit

e an

d ic

e sa

mpl

es a

lso

know

n as

6-a

min

ohex

anoi

c ac

id












091 090 100






















CONCLUSIONS









REFERENCES












































































091 090 100






















CONCLUSIONS









REFERENCES



















































































CONCLUSIONS









REFERENCES




































































REFERENCES

































































amino acid analyses of antarctic cm2 meteorites using liquid … · 2010-02-12 · amino acid...

Documents