Introduction Definition Structure of peptide bond Classes Dipeptides Tripeptides Polypeptides Peptide synthesis Liquid phase synthesis Solid phase synthesis General principle Steps Peptide overview Application Conclusion References

1. By
KAUSHAL KUMAR SAHU
Assistant Professor (Ad Hoc)
Department of Biotechnology
Govt. Digvijay Autonomous P. G. College
Raj-Nandgaon ( C. G. )

2. peptides
Synopsis
Introduction
Definition
Structure of peptide bond
Classes
Dipeptides
Tripeptides
Polypeptides
Peptide synthesis
Liquid phase synthesis
Solid phase synthesis
General principle
Steps
Peptide overview
Application
Conclusion
References

3. Introduction
All peptides and proteins are polymers of alpha-amino acids (AAs). Peptides are
short polymers of amino acid monomers linked by peptide bonds.AA is a molecule
that contains both amino (NH2) and carboxyl (COOH) functional groups. Each
amino acid has a different side chain (R group). The side chains vary greatly in
their properties. The general structure of an amino acid:
Fig-structure of amino acid

4. Peptide bond
AA are linked by amide bond[peptide bond] the resulting molecules is called peptide
and proteins. They are distinguished from proteins on the basis of size, typically
containing less than 50 monomer units.
Definition
A peptide bond is a covalent bond that is formed between two molecules when the
carboxyl group of one molecule reacts with the amino group of the another
molecule, releasing a molecule of water. This is a a condensation reaction and usually
occurs between amino acids. The resulting CO-NH bond is called a peptide bond, and
the resulting molecule is an amide.
Fig-peptide bond formation

5. Structure of peptide bond-
X-ray diffraction studies of crystals of small peptides by Linus Pauling and R. B.
Corey indicated that the peptide bond is rigid, and planer.
• Pauling pointed out that this is largely a consequence of the resonance interaction
of the amide, or the ability of the amide nitrogen to delocalize its lone pair of
electrons onto the carbonyl oxygen.
•Because of this resonance, the C=O bond is actually longer than normal carbonyl
bonds, and the N–C bond of the peptide bond is shorter than the N–Cα bond.
•It is notice that the carbonyl oxygen and amide hydrogen are in a trans
configuration, as opposed to a cis configuration. This configuration is energetically
more favorable because of possible steric interactions in the other.
N
C R
R'
O
N
C R
R'
O
Fig-formation of peptide bond

6. Figure -. Typical Bond Lengths Within a Peptide Unit. The peptide unit is
shown in the trans configuration.
Figure 3.25. Trans and Cis Peptide Bonds. The trans form is strongly
favored because of steric clashes that occur in the cis form

7. Classes of peptides-
Dipeptides –
Dipeptide is actually one molecule, which consists of 2 amino acids
that are joined by a single peptide bond.
Similarly there are also tripeptides, tetrapeptides, etc.
CH3
H3N C
O
O
CH
H3N C
O
O
CH2OH
H3N C
O
O
Alanine Serine
Valine
CH3
H3N C
H
N
O CH2OH
C
N
H
O
C
O
O
Tripeptide : Ala . Ser. Val
- 2 H2O

8. Polypeptide
A polypeptide is a long, continuous, and unbranched peptide. Proteins
consist of one or more polypeptides arranged in a biologically functional way
and are often bound to cofactors, or other proteins.

9. Peptide synthesis
Peptides are synthesized by coupling the carboxyl group or C-terminus of one amino
acid to the amino group or N-terminus of another. Due to the possibility of
unintended reactions, protecting groups are usually necessary.
There are two types of peptide synthesis-
1. Liquid-phase synthesis
Liquid-phase peptide synthesis is a classical approach to peptide synthesis. It has
been replaced in most labs by solid-phase synthesis . However, it retains usefulness
in large-scale production of peptides for industrial purposes.
2. Solid-phase synthesis
Solid phase peptide synthesis (SPPS), developed by R. B. Merrifield, was a major
breakthrough allowing for the chemical synthesis of peptides and small proteins.

10. General principle
•The general principle of SPPS is one of repeated cycles of coupling-
deprotection.
•The free N-terminal amine of a solid-phase attached peptide is
coupled to a single N-protected amino acid unit.
•This unit is then deprotected, revealing a new N-terminal amine to
which a further amino acid may be attached.
•There are two major used forms of solid phase peptide synthesis –
Fmoc (base labile alpha-amino protecting group) and t-Boc (acid
labile protecting group).
•Each method involves different resins and amino acid side-chain
protection and consequent cleavage/deprotection steps.

11. Fig- solid phase peptide synthesis by using fmoc protecting group

12. Steps
.The first stage of the technique consists of peptide chain assembly with
protected amino acid derivatives on a polymeric support.
The second stage of the technique is the cleavage of the peptide from the
resin support with the concurrent cleavage of all side chain protecting
groups to give the crude free peptide.
SOLID PHASE PEPTIDE SYNTHESIS
T
P
AA1 RX
anchoring
T
P
AA1 R
deprotection
P
AA1 R
T
P
AA2
coupling (-H2O)
T
P
AA2
P
AA1 R

13. T
P
AA2
P
AA1 R deprotection
coupling
repetitive
cycle
T
P
AAn
P
AA2
P
AA1 R
AAn
AA2 AA1
cleavage
+
final deprotection
Fig- solid phase peptide synthesis

14. Peptide overview
Bio-Synthesis is a leading global manufacturer of high quality custom-
synthesized peptides. It was successfully synthesized tens of thousands of
synthetic peptides for the biomedical research community, biotechnology
and pharmaceutical companies and have consistently met the highest
peptide standards of quality, service and technical expertise
Synthetic peptides are widely used for the following purposes:
- To verify the structure of naturally occurring peptides as determined by
degradation techniques.
- To study the relationship between structure and activity of biologically
active protein and peptides and establish their molecular mechanisms.
- To develop new peptide-based immunogens, hormones, vaccines, etc

15. Applications of
synthetic peptides
Immune peptides:
synthetic antigens;
vaccines
diagnostic tools
immunostimulator peptides;
muramyl dipeptide
tuftsin derivatives
Hormones:
oxytocin
vasopressin
insulin
somatostatin
GnRH
etc.
Neuropeptides:
substance P
cholecystokinin
neurotensin
Antibiotics:
tachikinin
gramicidine S
Toxins:
conotoxins
spider toxins
snake toxins
ionchanel blockers
Enzymes and
enzyme inhibitors:
Ribonuclease A
Carriers:
templates
miniproteins
Peptides
for structural studies:
turn mimicking cyclic peptides
Transporter peptides:
penetratin
oligoarginine
HIV-Tat protein

16. C-peptide
Proinsulin C-peptide was first described in 1967 in connection with the discovery of
the insulin biosynthesis.It serves as an important linker between the A- and the B-
chains of insulin and facilitates the efficient assembly, folding, and processing of
insulin in the endoplasmic reticulum. Equimolar amounts of C-peptide and insulin are
then stored in secretory granules of the pancreatic beta cells and both are eventually
released to the portal circulation.
Fig- structure of c peptide

17. Uses
•Newly diagnosed diabetes patients often get their C-peptide levels measured as a
means of distinguishing type 1 diabetes and type 2 diabetes. C-peptide levels are
measured instead of insulin levels because insulin concentration in the portal vein
ranges from two to ten times higher than in the peripheral circulation.
• The pancreas of patients with type 1 diabetes is unable to produce insulin, and,
therefore, they will usually have a decreased level of C-peptide, whereas C-peptide
levels in type 2 patients are normal or higher than normal.
•Measuring C-peptide in patients injecting synthetic insulin can help to determine
how much of their own natural insulin these patients are still producing.

18. Peptide hormone
•Peptide hormones are a class of peptides that are secreted into the blood
stream and have endocrine functions in living animals.
Notable peptide hormones
•The anterior pituitary secretes prolactin, which acts on the mammary gland,
adrenocorticotrophic hormone (ACTH), which acts on the adrenal cortex to
regulate the secretion of glucocorticoids, and growth hormone, which acts on
bone, muscle, and the liver.
•The posterior pituitary gland secretes antidiuretic hormone, also called
vasopressin, and oxytocin. Peptide hormones are produced by many different
organs and tissues, however, including pancreas (insulin and somatostatin),
the gastrointestinal tract cholecystokinin, gastrin).

19. •Some neurotransmitters are secreted and released in a similar
fashion to peptide hormones, and some 'neuropeptides' may be used
as neurotransmitters in the nervous system in addition to acting as
hormones when released into the blood. When a peptide hormone
binds to receptors on the surface of the cell, a second messenger
appears in the cytoplasm, which triggers intracellular responses
Diagnostic Peptides
Peptides can be designed that change color under certain conditions,
and these can be used for diagnostic purposes. For example, a
chromogenic peptide substrate can readily detect the presence,
absence and varying blood levels of enzymes that control blood
pressure and blood clotting ability.

20. Design of peptide enzymes (pepzymes):
surface-simulation synthetic peptides that mimic the chymotrypsin
and trypsin active sites exhibit the activity and specificity of the
respective enzyme
•Two 29-residue peptides were prepared, one of which (ChPepz) was
designed by surface-simulation synthesis to mimic the active site of alpha-
chymotrypsin, and the other (TrPepz), which contained four substitutions
relative to ChPepz, was fashioned after the active site of trypsin.
•The ChPepz monomer effected hydrolysis of the ester group in N-benzoyl-L-
tyrosine ethyl ester, an alpha-chymotrypsin substrate.
•ChPepz was completely inactivated by diisopropyl fluorophosphate (DIFP),
or reduction of the disulfide bond.

21. •TrPepz was fully inactivated by reduction of the disulfide bond,
by DIFP,
•It had no catalytic activity on N-tosyl-L-arginine methyl ester, a
trypsin substrate.
•This ability to construct fully functional peptide enzymes
(pepzymes) of chosen specificities should find many practical
applications.

23. References
•Biochemistry by Lubert styer 5th edition
•Biochemistry by lehninger 4th edition
•Harper’s lllustrated biochemistry by Robert k. murray 26th edition