25 advanced structural elucidation methods using the masspec algorithm and tandem mass spectral data...
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ADVANCED AUTOMATED SOLUTIONSFOR
STRUCTURE ELUCIDATION PROBLEMSUSING
THE MASSPEC ALGORITHM AND
TANDEM MASS SPECTRAL DATA
Marshall M. Siegel, Gary Walker
MS Mass Spec Consultants39-24 Grant St.
Fair Lawn, NJ 07410201 791 1627
CPSA 2012, October 3, 2012, Langhorne, PA
MASSPEC: Software for correlating chemical structures with mass spectra
1. Converts a chemical structure [or library of chemical structures (Batch Mode)]to superatom structures Postulate: Superatom substructures are NOT expected to fragment in the mass spectrometer.
2. Correlates superatom substructure masses with mass spectral fragment ion data3. Scores the fit of the fragment ion data to the superatom structures for obtaining the best
fitting chemical structure.
Applications1. Small Molecules (Natural Products, Pharmaceuticals, Metabolites, Polysaccharides, Peptides)
a. Known Structures: assign substructure to fragment ion massesb. Unknown Structures: Compare library of candidates to mass spectrum to find
highest scoring structure2. Metabolomics
a. Known pharmaceutical (Bonded Superatom), primary metabolite (Floating SA)b. Unknown metabolite: Compare a library of possible precursor candidate
structures to metabolite mass spectrum to find the highest scoring precursor structure
3. Proteomicsa. Determine sites of post-translational modificationsb. Analysis of peptide mixtures.
MASSPEC Characterization of Synthetic Heparin (Arixtra) with 10 Negative Charges
Bonded Superatoms Floating Superatoms
1. ESI CID MS/MS of [ M10- Na7+ ] 3-
2. 8 Sulfates, 2 Carboxylates, 6 Sugar OH’s (H2O)3. All ions converted to single negative charge4. All solutions have z = 1-; All excized ions are excluded.5. All glycosidic O’s expressed as H2O to account for H rearrangements.
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Metabolomics with MASSPEC –Scoring of Structures with Mass Spectrum
MS/MS Spectrumof Metabolite
Compare Spectrumwith List of
Superatom Structures
Obtain Matching Scorefor Each Natural Product
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NorcardamineMetabolite
561.3614 ; 100443.2506 ; 28401.2399 ; 24361.2448 ; 20319.2342 ; 60283.1289 ; 4243.1344 ; 100201.1237 ; 63183.1132 ; 1284.0804 ; 8
NorcardamineMetabolite
Norcardamine Norcardamine Superatoms
MASSPEC Exact Mass Analysis for an Unknown (Data Courtesy of Cerno Bioscience)
EI Mass Spectrum 20 Masses Analyzed
Three Classes of Proposed Elementals for the Unknown Parent Ions (D=Theory-Exp)
I: C6H12N2O4S2, D = -43.8 mmuII: C4H8N4O4S2, D = -18.7 mmu
III: C7H12O5S2, D = +32.0 mmu
m/z ; Intensity239.980 ; 17252.1211.990 ; 32430.4195.970 ; 495.7184.945 ; 439.7165.910 ; 36.3161.995 ; 80.8149.035 ; 2594.5146.965 ; 740.9141.835 ; 42.7131.980 ; 9673.2121.000 ; 10559.8118.975 ; 1485.9104.980 ; 738.993.955 ; 3801.591.975 ; 13936.975.955 ; 5682.664.930 ; 2524.858.000 ; 2083.947.965 ; 2633.442.025 ; 83276.3
Unknown Structure with MASSPEC – Scoring of Structures with Mass Spectrum
74 Structures (Mol Files)Converted Automaticallyto Superatom Structures
Highest Score BestStructural Fit
Modify Best Structure:ProduceHigher Scoring
Superatom Structure
MS000019
MS000027
MS000018
MASSPEC: A computer program for mass spectrometry that utilizes Combinatorics and Graph Theory Methods
to exhaustively compute 1. Superatom substructures of chemical structures, 2. Correlates substructure masses with mass spectral
fragment ion data3. Scores fragment ions based on mass accuracy (D) and
total number of disrupted bonds (N):
Score a {1/D and 1/N}
MASSPEC mimics an approach taken by applied mass spectrometrists to elucidate chemical structures.