proteins- structure & properties
TRANSCRIPT
Proteins….
-Peptide linkage-Stucture of proteins-Some properties
Hii…………..
PEPTIDE LINKAGE
Amino acid + amino acid amide -H2O
O H
C N
A link between -C=O groupOf 1 amino acid & -NHGroup of other amino acid
T think I am the strongest sinceI hav a lot of proteins
Dipeptide bond
Ala trp
Surprise……….surprise!!!!
Are you ready!!!!!!!
tripeptide
Ala trp pro
Hey…Smile beuties…..
tetrapeptide
cys
leu
tyr
ala
Friendship should be like this yaaar….
OLIGOPEPTIDE
Friends forever….
POLYPEPTIDE
The strongest of all….
STRUCTURE OF PROTIENS
Franz hofmiester -German scientist & physician-Observed biuret reactions in proteins-proteins-linear chains of alpha amino acids-1902
-Peptide model-amide linkage
Emil fischer
Hats off to them………
PRIMARY STRUCTURE
The order in which the amino acids are attached by peptide linkage.
Starts from N-terminal end to the C-terminal end.
The primary structure also requires specifyingthe cross-linking atoms, specifying the cysteinesinvolved in the protein's disulfide bonds.
Lets see in detail…
What does primary structure tell us??
sequence number composition kind
Order how many which one acidic basic neutral polar/non-polar
See the uses….
Determination of amino acid composition
Lets discover somthing
proteinsHydrolysepeptide bonds
Seperated amino acids
IndividualAmino acids
colour extracted
Amino acidCompositiondetermined
6N,HCl110 C ,24hrs
chromatography
Ninhydrin test
solvent
Advantage-Amino acid composition & kind can be determined
Disadvantage-Sequence cannot be determined
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Ayyoooooooooo…….
Determination of sequence of amino acids
End amino acid full sequence (atleast)
Sanger dansyl EDMANs degradationmethod chloride
Hey…one more thing
-introduced SANGER method-1953-Sequenced insulin -specific cleavage of protein & polypeptides
Frederick sanger
Well done sir……..
Sangers method/FDNB MethodFrederick Sanger -1953
FDNB + N-terminal of dinitrophenyl amino acid derivative(yellow)
End terminalAmino acid
Dansyl chloride + N-terminal of amino acid
Sulphonamidederivativecomplex
End terminal Amino acid formed
Its easy I think…..
EDMANs degradationDivide & conqure
First roundSecond round
First round
21 3 4 1 2 3 4
3 41 2+
+
Phenyliso- peptide phenylthiocarbomyl derivative thiocynate
Peptide shortenedBy 1 residue
labelling
release
The process repeats till the full sequence is determined.
Very imp..
Kaj Ulrik Linderstrøm
-Introduced primary structure of protein-in Stanford in 1953-he was elected as a Foreign Member of the Royal Society (ForMemRS)
We miss u sir…..
SECONDARY STRUCTURECoiling of the polypeptide chains through HYDROGEN BONDS.
Alpha helix beta-pleated sheet
Alpha-helixCoiling of the polypeptide chain so that the amino acids which are 3 to 4 positions apart are brought closer through hydrogen bonds.
C=O group of amino acid -NH group of 4rth amino acid
Distance between –adjacent amino acids – 1.5A - one turn – 5.4A
HYDROGENBONDED
Wooow I love those curly hairs!!
Hair is made up of a protein called keratin, which forms a helical shape.
This protein has sulfur bonds, and the more sulfur links it has, the curlier a person’s hair will be.
Lovely butterfly….
Beta-pleated sheetWhen 2 polypeptide chains or 2 separate regions in the same chains lie side by side that are connected by hydrogen bonds.
2 types-
PARALLEL
ANTIPARALLEL
WhatIs This??
Difference
Alpha-helix beta pleated sheet
1.Rod like2.Helical / coiled3.Common4.Adjacent amino acds-1.5A
1.Sheet like2.Fully extended3.Less common4.Adjacent amino acids-3.5A
Only 4 differences…???.
Tertiary structureFolding & refolding of the polypeptide chain to bring the amino acids closer that are far apart.
Eg 1.Myoglobin
-extremely compact-has 53 amino acid residues-75% ,8 helical regions-25%,non helical regions(proline)-interior-nonpolar AA-exterior-polar & nonpolar AA
CHARACTERISTICS-No disulphide bonds-contains heme
In humans,myoglobin is only found in the bloodstream after muscle injury.
It is an abnormal finding, and can be diagnostically relevant when found in blood. [2]
Eg2. Ribonuclease
-duck /kidney shaped-has 124 amino acids-4 disulphide bonds between 8 AA 26 40 58 65 S S S S S S S S
84 95 110 72
-NH end-lysine-COO end-valine
Oh my god!!!!It is first line defence against RNA virus
Its acts in RNA interference/post transcriptional gene silencing.
QUARTERNARY STRUCTURERefolding of multiple polypeptide chains ,ie-protein-protein interaction
Eg.haemoglobin – consists of 4 subunits - 2 alpha-2 haem parts - 2 beta -2 haem parts
Properties of proteins 1.AMPHOTERIC NATURE acids bases -ISOELECTRIC POINT (pI)+ve charges = -ve charges-net charge =0-solubility,osmotic pressure,viscosity = minimum
Ok….lets concentrate
2.DENATURATION-Lose of proteins biological activity due some external stress.
Physical organic solvents heavy metals-cooling -freezing-rubbing-agitation-heat-radiation
-ethanol-isopropanol
-Hg 2+-Ag+-Pb+
Wat to do now??
HOW DENATURATION OCCURS AT DIFFERENT LEVELS1.QUARTERNARYDissociation of protein subunits2.TERTIARY breakage of interactions
Covalent dipole-dipole vander-waals
3.SECONDARYDissociation of alpha helix & beta pleated sheet
ATTENSION- primary structure is the powerful one…….
Wat happened To my proteins??
DENATURATION OF EGG-IRREVERSIBLE
Denaturation ethyl alcohol-IRREVERSIBLE
Ayyo……
SO SAD KNO!!!!!!
Cataracts are caused by the denaturation of proteins in the lenses of the eyes.
RENATURATION-REVERSIBLE
Every action has an equal & opp reaction
Knowing about proteinswas interesting for me…
Hope for u all tooo….
Thnx……..