COVALENT AND WEAK NON-COVALENT BONDS IN MACROMOLECULES

PRESENTED TO: PRESENTED BY:

PROFESSOR OJASWI SINHA ABDUR RAHAMAN ASHWANI KUMAR SINGH ASHISH VERMA RAHUL TRIPATHI RISHABH CHAURASIYA

MACROMOLECULES INTERACTIONS

1.COVALENT INTERACTION

COVALENT BOND:

• A covalent bond is a chemical bond that involves the sharing of electron pairs between atoms.

• This electron pair is known as shared pairs or bonding electron, and the stable balance of a attractive and repulsive force between atoms, when they share electron is called covcalent bonding.

• TYPES OF COVALENT BOND :• A. Polar- e.g.-A water molecule, abbreviated

as H2O, is an example of a polar covalent bond• B. Non-Polar- e.g.- peptide bond

BIOLOGICAL SIGNIFICANCE OF COVALENT BOND :

1. Covalent bonds are strong enough to held macromoleculers chain together to preserve the sequence of subunits for long period of time.

2. One kind of non-polar covalent bond is very siginificant in macromolecules is called peptide bond.

3. A peptide bond joins together chains of amino acids,which involves in construction of DNA.

4. glycosidic bond (glycosidic link) The type of chemical linkage between the monosaccharide units of disaccharides, oligosaccharides, and polysaccharides, which is formed by the removal of a molecule of water.

COVALENT DRUGS

• Covalent drugs have made a major impact on human health and have been highly successful drugs for the pharmaceutical industry. These inhibitors react with their target proteins to form a covalent complex in which the protein has lost its function. The majority of these successful drugs, which include penicillin,omeprazole,and aspirin.

• Vigabatrin is an irreversible suicide inhibitor of gamma-aminobutyric acid transaminase (GABA-T), the enzyme responsible for the catabolism of GABA, which increases the level of GABA in the brain also comes under this category.

2.NON-COVALENT INTERACTIONS• Hydrophobic Effect Relese of water molecule from structured

solvation layer around the molecule as protein folds increased the net entropy.

• Hydrogen Bond Intraction of N-H and C=O of peptide bond

leads to local regular structures such as α-helix and β-sheets.

• London Dispersion Medium range weak attraction between all

atoms contributes significantily to the stablity in the interior protein.

• Electrostatic Interactions Long-range strong interactions between

permanently charged groups.

BIOCHEMICAL SIGNIFICANCE OF VAN DER WAALS INTERACTIONS

HYDROPHOBIC EFFECT

SIGNIFICACE OF NON-COVALENT INTERACTION

1. In aqueous environment each non-covalent bond is 30to300 times weaker than the typical covalent bond.

2. Unlike a single covalent bond non-covalent interactions are too weak to withstand the thermal motions that tends to pull molecules apart, and large number of non-covalent bonds are needed to hold two molecular surface together.

3. large number of non- covalent bond can form between two surface only when large number of atoms on the surface are precisely matched to each other, which accounts for the specificity of biological recognition, such as occur in between enzyme and substrate.

NON-COVALENT DRUGS• Reversible inhibitors bind non-covalently to

enzymes.• There are three kinds of reversible

inhibitors: competitive, noncompetitive, and uncompetitive inhibitors.

• Few examples of Reversible inhibitors:

• Acetylcholinesterase inhbitors:- Often abbreviated AChEI or anti-cholinesterase it is a chemical that inhibits the enzyme Acetylcholinesterase from breaking down acetylcholine.Common Drug- galantamine.

• Monoamine oxidase inhibitors:- Monoamine oxidase inhibitors (MAO inhibitors) inhibit one or both forms of the enzyme monoamine oxidase and prevent the breakdown of monoamine oxidase neurotransmitters.

REFERENCES1. Molecular biology of the cell,

volume 1 by Bruce Alberts.2. https://en.wikipedia.org/wiki/Non-

covalent_interactions3.

http://www.ncbi.nlm.nih.gov/books/NBK21726/

4. http://www.imsc.res.in/~sitabhra/teaching/cmp03/class4.html