Amino acid

Nonpolar Side Chains 
There are eight amino acids with nonpolar side chains. Glycine, alanine, and proline have small, nonpolar side chains and are all weakly hydrophobic. Phenylalanine, valine, leucine, isoleucine, and methionine have larger side chains and are more strongly hydrophobic.

Polar, Uncharged Side Chains 
There are also eight amino acids with polar, uncharged side chains. Serine and threonine have hydroxyl groups. Asparagine and glutamine have amide groups. Histidine and tryptophan have heterocyclic aromatic amine side chains. Cysteine has a sulfhydryl group. Tyrosine has a phenolic side chain. The sulfhydryl group of cysteine, phenolic hydroxyl group of tyrosine, and imidazole group of histidine all show some degree of pH-dependent ionization.

Charged Side Chains
There are four amino acids with charged side chains. Aspartic acid and glutamic acid have carboxyl groups on their side chains. Each acid is fully ionized at pH 7.4. Arginine and lysine have side chains with amino groups. Their side chains are fully protonated at pH 7.4.

This table shows amino acid names, three- and one-letter standard abbreviations, and linear structures. Click on the amino acid name for its Fischer projection formula (atoms in red are bonded to each other).

Name	Abbreviation	Linear Structure
Alanine	ala A	CH3-CH(NH2)-COOH
Arginine	arg R	HN=C(NH2)-NH-(CH2)3-CH(NH2)-COOH
Asparagine	asn N	H2N-CO-CH2-CH(NH2)-COOH
Aspartic Acid	asp D	HOOC-CH2-CH(NH2)-COOH
Cysteine	cys C	HS-CH2-CH(NH2)-COOH
Glutamic Acid	glu E	HOOC-(CH2)2-CH(NH2)-COOH
Glutamine	gln Q	H2N-CO-(CH2)2-CH(NH2)-COOH
Glycine	gly G	NH2-CH2-COOH
Histidine	his H	NH-CH=N-CH=C-CH2-CH(NH2)-COOH
Isoleucine	ile I	CH3-CH2-CH(CH3)-CH(NH2)-COOH
Leucine	leu L	(CH3)2-CH-CH2-CH(NH2)-COOH
Lysine	lys K	H2N-(CH2)4-CH(NH2)-COOH
Methionine	met M	CH3-S-(CH2)2-CH(NH2)-COOH
Phenylalanine	phe F	Ph-CH2-CH(NH2)-COOH
Proline	pro P	NH-(CH2)3-CH-COOH
Serine	ser S	HO-CH2-CH(NH2)-COOH
Threonine	thr T	CH3-CH(OH)-CH(NH2)-COOH
Tryptophan	trp W	Ph-NH-CH=C-CH2-CH(NH2)-COOH
Tyrosine	tyr Y	HO-Ph-CH2-CH(NH2)-COOH
Valine	val V	(CH3)2-CH-CH(NH2)-COOH

Amino Acid pKa and pI Values

Amino Acid	pKaC	pKaN	pKaR	pI
Glycine Alanine Valine Leucine Isoleucine Proline Serine Threonine Cysteine Methionine Asparagine Glutamine Phenylalanine Tyrosine Tryptophan Lysine Arginine Histidine Aspartate Glutamate	2.4 2.4 2.3 2.3 2.3 2.0 2.2 2.1 1.9 2.1 2.1 2.2 2.2 2.2 2.5 2.2 1.8 1.8 2.0 2.1	9.8 9.9 9.7 9.7 9.8 10.6 9.2 9.1 10.7 9.3 8.7 9.1 9.3 9.2 9.4 9.1 9.0 9.3 9.9 9.5	8.4 10.5 10.5 12.5 6.0 3.9 4.1	6.10 6.15 6.00 6.00 6.05 6.30 5.70 5.60 5.15 5.70 5.40 5.65 5.75 5.70 5.95 9.80 10.75 7.65 2.95 3.10

 Structures

Nonpolar (hydrophobic)

amino acid	three letter code	single letter code
glycine	Gly	G
alanine	Ala	A
valine	Val	V
leucine	Leu	L
isoleucine	Ile	I
methionine	Met	M
phenylalanine	Phe	F
tryptophan	Trp	W
proline	Pro	P

Polar (hydrophilic)

serine	Ser	S
threonine	Thr	T
cysteine	Cys	C
tyrosine	Tyr	Y
asparagine	Asn	N
glutamine	Gln	Q

Electrically Charged (negative and hydrophilic)

aspartic acid	Asp	D
glutamic acid	Glu	E

Electrically Charged (positive and hydrophilic)

lysine	Lys	K
arginine	Arg	R
histidine	His	H

Alanine ALA; A MW: 89.09 IE: 6.00 Formula: C3H7N1O2		Arginine ARG; R MW: 174.20 IE: 11.15 Formula: C6H14N4O2
Asparagine ASN; N MW: 132.12 IE: 5.41 Formula: C4H8N2O3		Aspartic Acid ASP; D MW: 133.10 IE: 2.77 Formula: C4H7N1O4
Cysteine CYS; C MW: 121.16 IE: 5.02 Formula: C3H7N1O2S1		Glutamic Acid GLU; E MW: 147.13 IE: 3.22 Formula: C5H9N1O4
Glutamine GLN; Q MW: 146.15 IE: 5.65 Formula: C5H10N2O3		Glycine GLY; G MW: 75.07 IE: 5.97 Formula: C2H5N1O2
Histidine HIS; H MW: 155.16 IE: 7.47 Formula: C6H9N3O2		Isoleucine ILE; I MW: 131.17 IE: 5.94 Formula: C6H13N1O2
Leucine LEU; L MW: 131.17 IE: 5.98 Formula: C6H13N1O2		Lysine LYS; K MW: 146.19 IE: 9.59 Formula: C6H14N2O2
Methionine MET; M MW: 149.21 IE: 5.74 Formula: C5H11N1O2S1		Phenylalanine PHE; F MW: 165.19 IE: 5.48 Formula: C9H11N1O2
Proline PRO; P MW: 115.13 IE: 6.30 Formula: C5H9N1O2		Serine SER; S MW: 105.09 IE: 5.68 Formula: C3H7N1O3
Threonine THR; T MW: 119.12 IE: 5.64 Formula: C4H9N1O3		Tryptophan TRP; W MW: 204.23 IE: 5.89 Formula: C11H12N2O2
Tyrosine TYR; Y MW: 181.19 IE: 5.66 Formula: C9H11N1O3		Valine VAL; V MW: 117.15 IE: 5.96 Formula: C5H11N1O2

CLICK ON THE NAME OF THE AMINO ACID TO SEE THE 3D IMAGE

Name Abbreviation	Mol Wt	pI	CAS Registry Number	Structure formula
Alanine ala a	89.09	6.00	56-41-7	CH3-CH(NH2)-COOH
Arginine  arg r	174.20	11.15	74-79-3	HN=C(NH2)-NH-(CH2)3-CH(NH2)-COOH
Asparagine  asn n	132.12	5.41	5794-13-8	H2N-CO-CH2-CH(NH2)-COOH
Aspartic acid  asp d	133.10	2.77	56-84-8	HOOC-CH2-CH(NH2)-COOH
Cysteine  cys c	121.15	5.02	52-90-4	HS-CH2-CH(NH2)-COOH
Glutamine  gln q	146.15	5.65	56-85-9	H2N-CO-(CH2)2-CH(NH2)-COOH
Glutamic acid  glu e	147.13	3.22	56-86-0	HOOC-(CH2)2-CH(NH2)-COOH
Glycine  gly g	75.07	5.97	56-40-6	NH2-CH2-COOH
Histidine  his h	155.16	7.47	71-00-1	N=C-NH-C=C-CH2-CH(NH2)-COOH |________|
Isoleucine  ile i	131.17	5.94	73-32-5	CH3-CH2-CH(CH3)-CH(NH2)-COOH
Leucine  leu l	131.17	5.98	61-90-5	(CH3)2-CH-CH2-CH(NH2)-COOH
Lysine  lys k	146.19	9.59	39665-12-8	H2N-(CH2)4-CH(NH2)-COOH
Methionine  met m	149.21	5.74	63-68-3	CH3-S-(CH2)2-CH(NH2)-COOH
Phenylalanine  phe f	165.19	5.48	63-91-2	Ph-CH2-CH(NH2)-COOH
Proline  pro p	115.13	6.30	147-85-3	NH-(CH2)3-CH-COOH |_________|
Serine ser s	105.09	5.68	56-45-1	HO-CH2-CH(NH2)-COOH
Threonine  thr t	119.12	5.64	72-19-5	CH3-CH(OH)-CH(NH2)-COOH
Tryptophan  trp w	204.23	5.89	73-22-3	Ph-NH-CH-C-CH2-CH(NH2)-COOH |_______|
Tyrosine  tyr y	181.19	5.66	60-18-4	HO-p-Ph-CH2-CH(NH2)-COOH
Valine  val v	117.15	5.96	72-18-4	CH3-CH(CH2)-CH(NH2)-COOH

 Grouping of amino acids based on their charges, hydorphobicity and polarity

Non-polar Hydrophobic		Negatively charged (acidic amino acids) Polar Hydrophilic		No charge (non-acidic amino acids) Polar Hydrophilic		Positively charged (basic amino acids; non-acidic amino acids) Polar Hydrophilic
Amino acid	pI	Amino acid	pI	Amino acid	pI	Amino acid	pI
Phenylalanine  phe f	5.48	Aspartic acid  asp d	2.77	Cysteine  cys c	5.02	Histidine  his h	7.47
Methionine  met m	5.74	Glutamic acid glu e	3.22	Asparagine  asn n	5.41	Lysine  lys k	9.59
Tryptophan  trp w	5.89			Glutamine  gln q	5.65	Arginine  arg r	11.15
Isoleucine  ile i	5.94			Threonine  thr t	5.64
Valine  val v	5.96			Tyrosine  tyr y	5.66
Leucine  leu l	5.98			Serine ser s	5.68
Alanine ala a	6.00			Glycine  gly g	5.97
Proline  pro p	6.30

Amino Acid Reference Data

The data in this table are for amino acid residues. To calculate the mass of a neutral peptide or protein, sum the residue masses plus the masses of the terminating groups (e.g. H at the N-terminus and OH at the C-terminus).

Residue	3- letter code	1- letter code	Mono- isotopic mass	Average mass	Structure
Alanine C3H5NO	Ala	A	71.037114	71.0779
Arginine C6H12N4O	Arg	R	156.101111	156.1857
Asparagine C4H6N2O2	Asn	N	114.042927	114.1026
Aspartic acid C4H5NO3	Asp	D	115.026943	115.0874
Asn or Asp	Asx	B
Cysteine C3H5NOS	Cys	C	103.009185	103.1429
Glutamic acid C5H7NO3	Glu	E	129.042593	129.114
Glutamine C5H8N2O2	Gln	Q	128.058578	128.1292
Glu or Gln	Glx	Z
Glycine C2H3NO	Gly	G	57.021464	57.0513
Histidine C6H7N3O	His	H	137.058912	137.1393
Isoleucine C6H11NO	Ile	I	113.084064	113.1576
Leucine C6H11NO	Leu	L	113.084064	113.1576
Lysine C6H12N2O	Lys	K	128.094963	128.1723
Methionine C5H9NOS	Met	M	131.040485	131.1961
Phenylalanine C9H9NO	Phe	F	147.068414	147.1739
Proline C5H7NO	Pro	P	97.052764	97.1152
Serine C3H5NO2	Ser	S	87.032028	87.0773
Threonine C4H7NO2	Thr	T	101.047679	101.1039
Selenocysteine C3H5NOSe	SeC	U	150.95363	150.0379
Tryptophan C11H10N2O	Trp	W	186.079313	186.2099
Tyrosine C9H9NO2	Tyr	Y	163.06332	163.1733
Unknown	Xaa	X
Valine C5H9NO	Val	V	99.068414	99.1311

The RNA Codons

Second nucleotide
	U	C	A	G
U	UUU Phenylalanine (Phe)	UCU Serine (Ser)	UAU Tyrosine (Tyr)	UGU Cysteine (Cys)	U
	UUC Phe	UCC Ser	UAC Tyr	UGC Cys	C
	UUA Leucine (Leu)	UCA Ser	UAA STOP	UGA STOP	A
	UUG Leu	UCG Ser	UAG STOP	UGG Tryptophan (Trp)	G
C	CUU Leucine (Leu)	CCU Proline (Pro)	CAU Histidine (His)	CGU Arginine (Arg)	U
	CUC Leu	CCC Pro	CAC His	CGC Arg	C
	CUA Leu	CCA Pro	CAA Glutamine (Gln)	CGA Arg	A
	CUG Leu	CCG Pro	CAG Gln	CGG Arg	G
A	AUU Isoleucine (Ile)	ACU Threonine (Thr)	AAU Asparagine (Asn)	AGU Serine (Ser)	U
	AUC Ile	ACC Thr	AAC Asn	AGC Ser	C
	AUA Ile	ACA Thr	AAA Lysine (Lys)	AGA Arginine (Arg)	A
	AUG Methionine (Met) or START	ACG Thr	AAG Lys	AGG Arg	G
G	GUU Valine Val	GCU Alanine (Ala)	GAU Aspartic acid (Asp)	GGU Glycine (Gly)	U
	GUC (Val)	GCC Ala	GAC Asp	GGC Gly	C
	GUA Val	GCA Ala	GAA Glutamic acid (Glu)	GGA Gly	A
	GUG Val	GCG Ala	GAG Glu	GGG Gly	G

The Genetic Code (DNA)

TTT	Phe		TCT	Ser		TAT	Tyr		TGT	Cys
TTC	Phe		TCC	Ser		TAC	Tyr		TGC	Cys
TTA	Leu		TCA	Ser		TAA	STOP		TGA	STOP
TTG	Leu		TCG	Ser		TAG	STOP		TGG	Trp
CTT	Leu		CCT	Pro		CAT	His		CGT	Arg
CTC	Leu		CCC	Pro		CAC	His		CGC	Arg
CTA	Leu		CCA	Pro		CAA	Gln		CGA	Arg
CTG	Leu		CCG	Pro		CAG	Gln		CGG	Arg
ATT	Ile		ACT	Thr		AAT	Asn		AGT	Ser
ATC	Ile		ACC	Thr		AAC	Asn		AGC	Ser
ATA	Ile		ACA	Thr		AAA	Lys		AGA	Arg
ATG	Met*		ACG	Thr		AAG	Lys		AGG	Arg
GTT	Val		GCT	Ala		GAT	Asp		GGT	Gly
GTC	Val		GCC	Ala		GAC	Asp		GGC	Gly
GTA	Val		GCA	Ala		GAA	Glu		GGA	Gly
GTG	Val		GCG	Ala		GAG	Glu		GGG	Gly

*When within gene; at beginning of gene, ATG signals start of translation.

Essential Amino Acids (Body cannot make these amino acids, they must come from food or amino acid supplements.)
	Amino Acid	Sym.	Abbr.	Min. Daily mg.	Acid Base Neu.	# of pathways - One Pathway	Generates	Works With (Against)	Augments
1	Isoleucine*	I	Ile	10	n	1 - threonine --> isoleucine	-	-	muscles
2	Leucine*	L	Leu	14	n	1 - keto-isovalerate --> leucine	-	-	blood, muscle, hormone
3	Lysine	K	Lys	12	B	2 - asparate --> lysine	-	calcium	herpes, triglycerides
4	Methionine	M	Met	13	n	7 - homoserine --> methionine	cysteine	selenium, zinc	hair, skin, chelator
5	Phenylalanine	F	Phe	14	n	3 - chorismate --> phenylalanine	tyrosine	B6	depression
6	Threonine	T	Thr	7	N	3 - aspartate --> threonine	glycine, serine	-	collagen, tooth enamel
7	Tryptophan	W	Trp	3.5	n	1 - chorismate --> tryptophan	niacin, seratonin	-	depression
8	Valine*	V	Val	10	n	1 - pyruvate --> valine	-	-	muscles
Food Sources: Fish - meat - poultry - cottage cheese - peanuts - lentils           A= acid, B= base, N= Neutral, n= non-polar           *= BCAA, Branched-Chain Amino Acids, all important in muscle recovery
-
Non-Essential Amino Acids (The body can make these amino acids from the above essential amino acids.)
	Amino Acid	Sym.	Abbr.	Min. Daily mg.	Acid Base Neu.	# of pathways - One Pathway	Generates	Works With (Against)	Augments
1	Alanine	A	Ala	-	n	4 - valine pyruvate --> alanine	-	-	-
2	Arginine*	R	Arg	-	B	4 - citrulline --> arginine	polyamines, creatine	zinc (lysine)	immune, healing, muscles
3	Asparagine	N	Asn	-	N	3 - asparate and ammonia	-	-	CNS
4	Aspartic Acid	D	Asp	-	A	3 - glutamate --> aspartate	-	-	CNS, brain
5	Cysteine	C	Cys	-	N	4 - serine --> cysteine	homocysteine, taurine	B6, Vit.E	skin, hair
6	Glutamic Acid	E	Glu	-	A	3 - ketoglutarate --> glutamate	glutamine, GABA	B6	brain
7	Glutamine	Q	Gln	-	N	2 - glutamate --> glutamine	-	-	brain
8	Glycine	G	Gly	-	N	2 - serine --> glycine	glutathione	GABA, taurine	body protein
9	Histidine*	H	His	-	B	1 - histidinol --> histidine	histamine	-	blood, allergy, sex
10	Proline	P	Pro	-	n	4 - l-glutamine --> proline	hydroxyproline	Vitamin C	collagen, elastin
11	Serine	S	Ser	-	N	1 - phosphoglycerate --> serine	cysteine, glycine	choline	blood sugar
12	Tyrosine	Y	Tyr	-	N	2 - phenylalanine --> tyrosine	thyroxin, melanin	B6	thyroid
* = These are Essential for infants, since their bodies cannot produce them yet.
-
Other Amino Acid Factors
-	Carnitine	-	Car	-	-	carnitine --> butyrobetaine -->	Lysine, methionine	Vitamin C	fat metabolism
-	Citrulline	-	Cit	-	-	argenine --> citrulline --> ornithine	Ornithine	zinc	urea cycle
-	Hydroxyproline	-	Hyp	-	-	proline --> hydroxyproline	-	Vitamin C	collagen
-	Ornithine	-	Orn	-	-	argenine --> citrulline --> ornithine	-	-	urea cycle
-	Taurine	-	Tau	-	-	methionine --> cysteine --> taurine	GABA, glycine	B6	heart, bile
The above are precursors for, or important products of, the 20 "true" amino acids listed above.

Codes

AA Residue Composition

Mono.

Avg.

Structure

I O N S O U R C E . C O M

AA Codes

AA Residue Composition

Mono.

Avg.

Structure

Gly

G

C2H3NO

57.021464

57.05

Asp

D

C4H5NO3

115.02694

115.1

Ala

A

C3H5NO

71.037114

71.08

Gln

Q

C5H8N2O2

128.05858

128.1

Ser

S

C3H5NO2

87.032029

87.08

Lys

K

C6H12N2O

128.09496

128.2

Pro

P

C5H7NO

97.052764

97.12

Glu

E

C5H7NO3

129.04259

129.1

Val

V

C5H9NO

99.068414

99.07

Met

M

C5H9NOS

131.04048

131.2

Thr

T

C4H7NO2

101.04768

101.1

His

H

C6H7N3O

137.05891

137.1

Cys

C

C3H5NOS

103.00919

103.1

Phe

F

C9H9NO

147.06841

147.2

Leu

L

C6H11NO

113.08406

113.2

Arg

R

C6H12N4O

156.10111

156.2

Ile

I

C6H11NO

113.08406

113.2

Tyr

Y

C9H9NO2

163.06333

163.2

Asn

N

C4H6N2O2

114.04293

114.1

Trp

W

C11H10N2O

186.07931

186.2

H	1.0078250,	1.008	O	15.994915,	16.00	OH	17.00274,	17.01	H20	18.01057,	18.02	NH3	17.02655,	17.03
CH3*	14.01565,	14.03	CH3CO*	42.01057,	42.04
* The mass of these groups observed after the displacement of a proton, for example the addition of a methyl group CH3 should displace a proton and thus the mass change is equivalent to the addition of CH2.  See our policy for rounding and significant figures.

Best Wishes: Dr.Ehab Aboueladab, Tel:01007834123 Email:ehab10f@gmail.com,ehababoueladab@yahoo.com