1. By
A. k. jangid
School of chemical science
CUG
Email:-ashok4483@gmail.com

2.  Introduction
 Protein and peptide
 Peptide bond and its Machanism
 Characteristics of peptide
 Methods of peptide synthesis
 Protein structure(Linus pauling
structure)

3. • As muscles and tendons they provide the body with the
means for movement; as skin and hair they give it an outer
covering.
• Proteins are polyamides, and their monomeric units are
composed of about 20 different a-amino acids.
• Proteins occur in every living
organism, are of many different
types, and have many different
biological functions.
• The three groups of biological
polymers are polysaccharides,
proteins, and nucleic acids.
• As enzymes and hormones, proteins
catalyze and regulate the reaction
that occur in the body.

4. • Oligopeptide is formed of (2 – 10 ) amino acids:
2 amino acids dipeptide,
3 amino acids tripeptide,
4 amino acids tetrapeptide ….etc.
• Polypeptide is formed of more than 10 amino acids
• All proteins are polymers of
amino acids.
• Each protein polymer
(polypeptide chain) consists of a
sequence of 20 different amino
acids connected together by
peptide bonds.
• For chains under 40 amino acid
residues, the term peptide is
frequently used instead of
protein.

5. • This is a dehydration synthesis reaction (also
known as a condensation reaction).
• The four-atom functional group -C(=O)NH- is
called an amide group or (in the context of
proteins) a peptide group.
• Peptide bond is an amide
linkage between the
carboxyl group of one
amino acid and the amino
group of another amino
acid formed by
condensation reaction with
removal of one molecule
of water.

6. N
H
H CH
COO
R
AMINO ACID
H2O H2O
N
H
H CH
H
C
R
O
N
CH
H
COO
R
PEPTIDE GROUP

7. • Cis and Trans Peptide Bonds
• Resonance
C
O
N C
O
N
C
O
C
N
C
H
alfa c atom
alfa c atom
C N
O
C
H
C
alfa C atom
alfa C atom
CH
O
C
H2
N
H2
C
H
cis trans

8. Coupling
Deprotection
 Formation of peptide bond it is necessary that the
OH Group present in the carboxylic acid function is
convert into a good leaving.
COOH group is to convert in to acyle group.
In this method ,the protected amino acid is
converted to the corresponding acyl chloride
followed by reaction with amino acid or ester under
Schotten - -Baumann condition or treatment with
amino ester in organic solvents to give the N-
protected peptide.
Deportection under hydrolytic condition give the
free peptide.
2HN
H
C
R
COOH
SOCl2
N
H
C
R1
CO Cl
H
H
2H N
H
C
R2
C
O
OCH3
2HN
H
C
R1
C
O
N
H
H
C
R2
COCH3
H
C C
O
N
H
H
C
R2
COOH
R1
N
H
H

9. • Structure of protein divided into 4 levels.
• Primary structure
• Secondary structure
• Tertiary structure
• Quaternary structure
• Protein molecule can be
formed of one or more
polypeptide chains which
may vary in the number and
sequence of amino acid
residues.

10. N CH C
R
N
O
*
H H
H
C C N
O
R
H
H
C
R
C
O
n
Primary structure of protein refers to linear
Secquence of amino acid in its polypeptide
chain . It represent the number,nature and
Sequence of amino acid molecule in the poly-
-peptide chain.
Example:- simple polypeptide chain.

11. It results by hydrogen bonding between
carboxylic oxygen and amide hydrogen atom
of the component amino acid of the peptide
chain.
These hydrogen bonded arrangement ,if
present ,are called secondary structure of
protein.
• These bond can occure either with in the molecule of one
polypeptide chain forming alpha-helix plated sheet.
• The alpha-helix structure of protein was first proposed by Linius
pauling and Robert corey using X ray analysis of protein.
• In the alpha-helix (look like the right hand screw) conformation,the
polypeptide chain form of spiral staircase.
• The coil of helix are held together by hydrogen bond laying
parallel to the main axis and all side chain extend outward form
the axis of the spiral.
• Such a structure is flexible and elastic but it gives stability of the
peptide chain.
The folding of linear polypeptide chain in to a
specific arrangement, represents the
secondary structure of a protein molecule.

12. • "for his research into the nature of the chemical bond and its
application to the elucidation of the structure of complex
substances"
Example : - hairs protein ,nails protein etc.

13.  The quaternary structure involves the non covalent association
of two or more peptide chain in protein molecule.
 Having more than peptide chain so called oligomers.
 In this structure same kind of interaction that hold the
individual protein chain in a particular three dimensional
conformation.
 They are hydrophobic interactions, hydrogen bond and electro-
- static interaction. It decribe the way of subunits are arrange in
space.
 Example: hemoglobin form a globular protein.
 Tertiary structure of a protein
is the final three dimensional
shape due to folding its poly-
peptide chain.
 Protein folds in solution have
maximum stability due to that
occur in folding are covalent –
bond ,hydrogen bond and
vanderwaals or hydrophobic
interaction.
 Example –alpha
Keratin,fibrous-
protein

14. For your kind attention !!!!!!!!!!!