Proteins may be broken into their constitutent monomer molecules by hydrolysis. AminoAcid products of the reaction constitute the AminoAcid composition of the Proteins.

  • Standard AminoAcid : 20 amino acids found in Proteins

  • Nonstandard AminoAcid : chemically mdified after their incorporation into a polypeptide and amino acids that occur in living organisms but are not found in Proteins. e.g.taurin

These molecules contain a central carbon atom (alpha-carbon) to which an amino group, a carboxylate group, a hydrogen atom, and an R(side chain) group are attached.

At a pH of 7 the carboxyl group of an AminoAcid is in its conjugate base form (-COO-) and the amino group is in its conjugate acid form (-NH3+). Thus each AminoAcid can behave as either an acid or a base. It's called Amphoteric property of a AminoAcid. Neutral molecules that bear an equal number of positive and negative charges simultaneously are called zwitterions. It is the R group, however, that gives each AminoAcid its unique properities. Also the pH value that AminoAcid's net charge become zero is called IsoelectricPoint.

Names and Abbreviations of the Standard amino acids

AminoAcid

Three-Letter

One-Letter

Alanine

Ala

A

Arginine

Arg

R

Asparagine

Asn

N

Aspartic acid

Asp

D

Cysteine

Cys

C

Glutamic acid

Glu

E

Glutamine

Gln

Q

Histidine

His

H

Isoleucine

Ile

I

Leucine

Leu

L

Lysine

Lys

K

Methionine

Met

M

Phenylalanine

Phe

F

Proline

Pro

P

Serine

Ser

S

Threonine

Thr

T

Tryptophan

Trp

W

Tyrosine

Tyr

Y

Valine

Val

V

Special AminoAcid

SelenoCystein

Sec

U

Classification of Amino acids

  • Group I : Hydrophobic - Nonpolar side Chains
    • Ala, Val, Leu, Ile, Pro, Met, Phe, Trp
    Group II : Polar, unchanged
    • Gly, Ser, Thr, Cys,Tyr, Asn, Gln
    Group III : Acidic
    • Asp, Glu
    Group IV : Basic
    • Lys, Arg, His

Properties of each Amino acids

♣Histidine(His, H)

  • Unique imidazole side chain: effective as nucleophilic catalyst( more basic than hydroxide ion)

    five-membered ring structure --> relatively little steric hindrance pKa = 7

<Aromatic Residues>

  • Has UV absorbance and fluorescence properties of proteins.

AminoAcid chart

http://www.ionsource.com/virtit/VirtualIT/chart1.gif

필수 AminoAcid

체내에서 합성이 되지 않기 때문에 반드시 섭취해야 하는 8가지 AminoAcid들

  • Ile, Leu, Val, Lys, Phe, Trp, Met, Thr

AminoAcid (last edited 2011-08-03 11:00:46 by localhost)

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