Chem 30B Dr. R. Rinehart
Chapter 19: Amino Acids and Proteins
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Amino Acids: alphabetically, "classic"

Name

3-letter abbreviation

1-letter abbreviation

structure
drawn without
showing ionization

comments

alanine

ala

A

R is small, nonpolar

arginine

arg

R

R is ⊕ at pH 7
contains the guanidino group
semi-essential

asparagine

asn

N

R is polar but neutral; the amide N can serve as attachment point for sugars

aspartic acid or
aspartate

asp

D

R is ⊝ at pH 7; often found at active site of enzymes

cysteine

cys

C

sulfur-containing; its thiol group is frequently found at enzyme active sites; oxidation of the thiol to a disulfide is important in 3^o and 4^o structure of proteins

glutamine

gln

Q

R is polar but neutral

glutamic acid or
 glutamate

glu

E

R is ⊝ at pH 7
familiar as the food additive MSG;
also a neurotransmitter

glycine

gly

G

the simplest amino acid and the only one not of the L- configuration; R is nonpolar, but not very

histidine

his

H

R is ⊕ at pH 7 [~40%]
contains the imidazole group;
found very often at enzyme active sites;
semiessential

isoleucine

ile

I

R is bulky, very nonpolar
diet-essential

leucine

leu

L

R is bulky, very nonpolar
diet-essential

lysine

lys

K

R is ⊕ at pH 7
diet-essential

methionine

met

M

R is bulky, very nonpolar
diet-essential

phenylalanine

phe

F

R is bulky but planar, very nonpolar;
diet-essential

proline

pro

P

an “imino acid”; introduces kinks in protein chains; the N is unable to H-bond when in a protein chain

serine

ser

S

R is polar but neutral
found at active site of many enzymes

threonine

thr

T

R is polar but neutral; diet essential

tryptophan

trp

W

R is extremely bulky, nonpolar; the NH of the indole ring can H-bond;
diet-essential

tyrosine

tyr

Y

R is bulky, nonpolar except for the –OH group, which can ionize at pH>10; the –OH can be phosphorylated as a mechanism of enzyme control by “tyrosine kinases”

valine

val

V

R is bulky, very nonpolar
diet-essential

 © Ronald W. Rinehart, 2002  Structures drawn with ACD Labs ChemSketch^®

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