PROTEIN

PROTEIN :-

     Proteins are complex nitrogenous organic bio-polymer of amino caids showing great diversity in their organization and are of prime biological importance
- These protein are formed by interlinking of two or more amino acids by peptide bonds

- There is about 7 Non-polar amino acid named as

* Serine
* Threonine
* Glycine
* Cysteine
* Tyrosine
* Aspargnine
* Glutamine
- There is about 8 Polar amino acids named as :-
* Alanine
* Valine
* Proline
* Metheonine
* Isoleucine
* Phenyl Alanine
* Tryptophan
* Proline
- There is about Acidic amino acid also are
* Aspartic acid
* Glutamic Acid
- Basic amino acids are :-
* Lysine
* Arginine
* Histidine
- If a chain having less than 30 Chain of Amino acid = Oligopeptide
- if A Chain having More Than 30 Chain of amino acid = polypeptide

@ Structure Of Protein molecule

i) Primary Structure :-

          these protein having linear arrangements of amino acids in poly peptide chain
- Minimum 20 amino acids need to form a functional chain of protein chain
- In this structure peptide bond act as back bone
- Ex :- Insulin , having 3 chain with A=21, B=30, C=33 amino acids respectively

ii) Secondary Structure :-

          In this amino acids have conformational arrangement which results in bending and folding of amino acids
- In this mainly three type of structure are found as

# ɑ-helix Structure :-

             ~ In this Polypeptide chain spirally coiled to form ɑ-helix and 3D form along longitudinal axis of molecule, so provide a condense structure
~ R-group of amino acid protrude form helical backbone
~ Each spiral is completed about 5.4 angstron from helical backbone and diameter about 6 angstron
~ ɑ-helix  is stabilize is due to presence of a series of regularly spaced intermoleculer hydrogen bond between every imide hydrogen (NH) and electron-negative of carbonyl oxygen of 4th Amino acid behind it in helix
~ As intramolecule is 1.5 angstron (distance) , so on average each helix contain about 3.6 Angstron
~ ɑ-helix is most stable in secondary structure
~ ɑ-helix may form right or left handed
~ ɑ-helix right handed more stable ,especially when formed og L-amino acis

# β- Pleated Structure :-

         * it ia an extended structure , in which protein is form of number of polypeptide chain side by side
* In this adjacent polypeptide chain run either in opposite direction ( anti- parellel ) or in same direction (parellel )
* Amino acid of polypeptide are spaced are 3.5  angstron
* Amino acid rotated 180 degree with respect to adjacent amino acids residue
* There are intermoleculer H-bond between Imide (NH) and carboxylic (CO) of adjacent polypeptide chain maximum H-bonding is possible in antiparellel structure
* There are cystein residue, no disulphide linkage between adjacent chain

# Random coil

iii) Tertiary structure :-

         it refer to bending ,folding of polypeptide chain to form compact tightly folded and 3D globuler structure
- A Polupeptide chain take 3D shape, so is either spherical globular or squiodal or irregular
       so compactly folded that there is little and no arrranged one axis chain remain in one axis, bit it is irregular

=> Stabilize :-

* By four different type forces are ionic, hydrogen,disulphide, hydrophobic interaction respectively
- Due to folding of chain distantly placed active chain of amino acid came closer and form active site enzymatic protein
- Ex :-
* Myoglobin
* Lysozyme
* Carboxy-peptide -A

* Cytochrome-C :-

             highly condensed sequence
* Lactase dehydrogenase
* Chymotrypsin

iv) Quarternery structure :-

              relative arrangement of two or more similar and dissimilar upon one another and united by forces other than covalent and disulphide bond

@ General properties :-

- Having Amorphous nature
- Having Colloidal properties
- Zwitter ion Structure
- Amphoteric Nature
- Having Definate Isoelectric focussing

@ Denaturation :-

         it is type of process in which it all bonds break off and became non functional , this denaturation can be cause by temperature change, change in pH or by chemical