Proteins- structure & properties

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

Aey…………….

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……..