Reference table

Amino Acid Codes Table

This table lists the 20 standard amino acids with their one-letter code, three-letter code, RNA codons, side-chain class, molecular weight, and links to detailed amino acid pages.

20 Standard Amino Acids

Amino acid	One-letter	Three-letter	Codons	Category	Molecular weight
Alanine	A	Ala	GCU GCC GCA GCG	Nonpolar	89.09 Da
Arginine	R	Arg	CGU CGC CGA CGG AGA AGG	Basic	174.20 Da
Asparagine	N	Asn	AAU AAC	Polar	132.12 Da
Aspartic Acid	D	Asp	GAU GAC	Acidic	133.10 Da
Cysteine	C	Cys	UGU UGC	Sulfur-containing	121.02 Da
Glutamic Acid	E	Glu	GAA GAG	Acidic	147.13 Da
Glutamine	Q	Gln	CAA CAG	Polar	146.15 Da
Glycine	G	Gly	GGU GGC GGA GGG	Nonpolar	75.07 Da
Histidine	H	His	CAU CAC	Basic	155.16 Da
Isoleucine	I	Ile	AUU AUC AUA	Nonpolar	131.17 Da
Leucine	L	Leu	UUA UUG CUU CUC CUA CUG	Nonpolar	131.17 Da
Lysine	K	Lys	AAA AAG	Basic	146.19 Da
Methionine	M	Met	AUG	Sulfur-containing	149.21 Da
Phenylalanine	F	Phe	UUU UUC	Aromatic	165.19 Da
Proline	P	Pro	CCU CCC CCA CCG	Nonpolar	115.13 Da
Serine	S	Ser	UCU UCC UCA UCG AGU AGC	Polar	105.09 Da
Threonine	T	Thr	ACU ACC ACA ACG	Polar	119.12 Da
Tryptophan	W	Trp	UGG	Aromatic	204.23 Da
Tyrosine	Y	Tyr	UAU UAC	Aromatic	181.19 Da
Valine	V	Val	GUU GUC GUA GUG	Nonpolar	117.15 Da

How to Use Amino Acid Codes

One-letter codes are used in compact protein sequences, while three-letter codes are common in structure files, teaching materials, and biochemical references.

Follow any codon link to see which amino acid it encodes, its DNA equivalent, synonymous codons, and anticodon pairing.

Amino Acid Codes Table

20 Standard Amino Acids

How to Use Amino Acid Codes

Related Tools