Download Physical properties of amino acids: Chemical properties of amino

Physical properties of amino acids:
Colorless, crystals, soluble in water, insoluble in ether.
All amino acids( except glycine) are optically active.
Amphoteric (react as acidic and basic), (NH2 and COOH group).
Chemical properties of amino acids: 2 reactive groups
A – COOH Reactions:
1-Ester with alcohol
Amino acids react with alcohol to form ester.
COO
COOH
COOR
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HCl
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NH3—CH—————> ClNH3—C—H————> ClNH3—C—H
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R
R
R
2-With NH3 Amidation.
Aspartic acid ————> Aspargine
Aspartic acid
Aspargine
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+ H2O
3-Reduction by LiAlH4
LiAlH4
R—CH—(NH2)—COOH—————> R—CH—(NH2)CH2OH
Amino alcohol
4-Decarboxylation
B –NH2 Reaction:
1-Salts with acids
H
H
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HCl
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R—C—COOH—————> R—C—COOH
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NH2
NHCl
2-Acylation: Reaction with strong acids
(Acid anhydride + NaOH)
2
3-Methylation and benzoylation: important, detoxification process.
4-With Sanger s reagent (1-floro-2,4-di nitro benzene).
FDNB
Amino acid + DNFB————> Di nitro phenyl amino acid
Is a test for free amino acid.
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5-With nitrous acids HNO2 ——> Oxo acid.
H
H
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R—C—COOH+ HNO2————> R—C—COOH + N2 + H2O
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NH2
OH
N2= measure of free NH2 group in protein or peptide.
6-Oxidative deamination (Removal of NH2)
H
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R—C—COOH————> R—C—COOH———>R—C—COOH+NH3
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NH2
NH
O
Oxo acid (keto acid)
7-Ninhydrin reaction
Hydrindentin
Quantitative measurement of free α- amino group .
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Peptide bonding
A covalent bond that links amino acids together in protein.
( α- amino group of amino acid with α- COO group of another amino acid) .
Polypeptide: many repeated peptide bonds. Biological active protein contain
1 or more polypeptide chains.
Small polypeptides of biological activity:
1-Lue.-Encephalin and Met.- Encephalin (5 amino acid)
Try.-Gly.-Gly.-Phe.-Lue.
Tyr.-Gly.-Gly.-Phe.-Met.
Relieve pain centrally.
2-Angiotensin II (8 amino acids)
Asp.-Arg.-Val.-Tyr.-Ilu.-His.-Pro.-Phe.
(vasoconstrictor) hormone.
3-Vasopressin (9 amino acids)
Cys.-Tyr.-Phe.-Gln.-Asn.-Cys.-Pro.-Arg.-Gly.
(antidiuretic hormone), acts on kidney tubules to prevent dieresis, secreted
by the pituitary gland.
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4-Gramicidine-S (2 chain of 5 amino acids)
Antibiotic: for Bacillus, breuis.
Derived amino acids (modified amino acids)
Found in certain protein.
1-Cystine: oxidize Cysteine
2- 4-hydroxy Prolin and 4-hydroxy Lysine
3-Phospho Serine
Casein of milk, some enzymes.
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4-Phospho Tyrosine
(cancer research)
5-N-formyl methionine
Essential for protein synthesis in E-coli.
6-Amino acids not related to protein synthesis
Homoserine
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Ornithin
Urea cycle intermediate
Essential amino acids
Histidine, Leucine, Isoleucine, Lysine, Methionine, Phenyl alanine,
Threonine, Tryptophan, Valine.
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