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Amino Acids

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R CH

NH2

COOH

Classification

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The general structure of an alpha (α) amino acid.

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Isomerism1)Chain2)Functional groups position

CH CH COOH

NH2

CH3

CH2CH3

CH2 CH COOH

NH2

CHCH3

CH3

CH2 CH2 COOH

NH2

CH3 CH COOH

NH2

Leucine Isoleucine

α-Alanine β-Alanine

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3)Optical Isomerism - Enantiomerism

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COOH

CH3

H2N H

COOH

CH3

H NH2* *

MIRROR PLANE

L - Alanine D - Alanine

(L)-Alanine (left) and (D)-alanine (right) in zwitterionic form at neutral pH

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Chemical Properties1. Dipolar ion (dipolar salt)

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2. Amphoterizm As an acid.

CH3 CH COOH

NH2

+ NaOH CH3 CH

NH2

COONa + OH2

CH3 CH COOH

NH2

+ ClH CH3 CH

NH3

COOH

+Cl

As a base

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3. Complex salt

CH3 CH COOH

NH2

2 + Cu(OH)2

Cu

NH2

OC

O

CH3

NH2

OC

O

CH3

+ OH22

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4. Specifical Reactionsa) Inter molecular

O O H

N HCH3

H

OOH

NH CH3

H

ON

N CH3O

CH3

H

H

+ 2 H2Ot

Diketopiperazine

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b) Intra molecular

c) Intra molecular

+ NH3

tCH2 CH2 COOH

NH2

CH2 CH COOH

+ H2Ot

C

O

OHCH2

CH2

CH2 N H

H

C

O

CH2

CH2

CH2

N H

-Aminobutyric acid Butyrolactam

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5. Reaction with nitrous acid

6. Metabolic reactions1)Decarboxylation

R CH COOH

NH2

R CH COOH

OH+ HNO2 + N2 + OH2

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R

CH

COOH

NH2

FMN oxydaza Laa FMN*H2

FAD oxydaza Daa FAD*H2

R

CH

COOH

NH

R

CH

COOH

O NH3

- H2O+

CH3 CH

NH2

COOH CH3 CH

OH

COOHHOH NH3+ +

2) Deaminationa) Oxydative deamination

b) Hydrolytic deamination

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CH3 CH

NH2

COOH CH3 CH2 COOH NH3H ++2

c) Reductive deamination

d) Intra molecula deamination

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3. Transamination

4. Peptide bond formation

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The condensation of two amino acids to form a peptide bond.

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The Biuret test is a chemical test used for detecting the presence of peptide bonds. In the presence of peptides, a copper(II) ion forms a violet-colored complex in an alkaline solution. Several variants on the test have been developed.

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Protein structure

Three possible representations of the three-dimensional structure of the protein triose phosphate isomerase. Left: all-atom representation colored by atom type. Middle: Simplified representation illustrating the backbone conformation, colored by secondary structure. Right: Solvent-accessible surface representation colored by residue type (acidic residues red, basic residues blue, polar residues green, nonpolar residues white).

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Most proteins fold into unique 3-dimensional structures. The shape into which a protein naturally folds is known as its native conformation. Although many proteins can fold unassisted, simply through the chemical properties of their amino acids, others require the aid of molecular chaperones to fold into their native states. Biochemists often refer to four distinct aspects of a protein's structure:

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•Primary structure: the amino acid sequence.•Secondary structure: regularly repeating local structures stabilized by hydrogen bonds. The most common examples are the alpha helix, beta sheet and turns. Because secondary structures are local, many regions of different secondary structure can be present in the same protein molecule.

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•Tertiary structure: the overall shape of a single protein molecule; the spatial relationship of the secondary structures to one another. Tertiary structure is generally stabilized by nonlocal interactions, most commonly the formation of a hydrophobic core, but also through salt bridges, hydrogen bonds, disulfide bonds, and even post-translational modifications. The term "tertiary structure" is often used as synonymous with the term fold. The tertiary structure is what controls the basic function of the protein.

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•Quaternary structure: the structure formed by several protein molecules (polypeptide chains), usually called protein subunits in this context, which function as a single protein complex.

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Proteins are not entirely rigid molecules. In addition to these levels of structure, proteins may shift between several related structures while they perform their functions. In the context of these functional rearrangements, these tertiary or quaternary structures are usually referred to as "conformations", and transitions between them are called conformational changes.

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Such changes are often induced by the binding of a substrate molecule to an enzyme's active site, or the physical region of the protein that participates in chemical catalysis. In solution proteins also undergo variation in structure through thermal vibration and the collision with other molecules.

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Molecular surface of several proteins showing their comparative sizes. From left to right are: immunoglobulin G (IgG, an antibody), hemoglobin, insulin (a hormone), adenylate kinase (an enzyme), and glutamine synthetase (an enzyme).Proteins can be informally divided into three main classes, which correlate with typical tertiary structures: globular proteins, fibrous proteins, membrane proteins.

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Almost all globular proteins are soluble and many are enzymes. Fibrous proteins are often structural, such as collagen, the major component of connective tissue, or keratin, the protein component of hair and nails. Membrane proteins often serve as receptors or provide channels for polar or charged molecules to pass through the cell membrane.

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Thank You!

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