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Amino Acid Structures, Codes and Reference Information

Amino acid structures and peptide bond formation depictions. Amino acid single-letter and three-letter codes and molecular weights.

Amino Acid Structures.

Amino Acid Structures.

Amino Acid Abbreviations and Molecular Weights.

Amino Acid Three-Letter Abbreviation One-Letter Symbol Molecular Weight
Alanine Ala A 89Da
Arginine Arg R 174Da
Asparagine Asn N 132Da
Aspartic acid Asp D 133Da
Asparagine or aspartic acid Asx B 133Da
Cysteine Cys C 121Da
Glutamine Gln Q 146Da
Glutamic acid Glu E 147Da
Glutamine or glutamic acid Glx Z 147Da
Glycine Gly G 75Da
Histidine His H 155Da
Isoleucine Ile I 131Da
Leucine Leu L 131Da
Lysine Lys K 146Da
Methionine Met M 149Da
Phenylalanine Phe F 165Da
Proline Pro P 115Da
Serine Ser S 105Da
Threonine Thr T 119Da
Tryptophan Trp W 204Da
Tyrosine Tyr Y 181Da
Valine Val V 117Da
The average molecular weight of an amino acid is 110Da. Dalton (Da) is an alternate name for the atomic mass unit, and kilodalton (kDa) is 1,000 daltons. Thus a protein with a mass of 64kDa has a molecular weight of 64,000 grams per mole.

Peptide Bond Formation.

Peptide Bond Formation.

R1 and R2 represent the R groups of the two amino acids.

 

 

The Genetic Code.

1st Position 2nd Position 2nd Position2 2nd Position3 2nd Position4 3rd Position
U C A G
U UUU Phe UCU Ser UAU Tyr UGU Cys U
U UUC Phe UCC Ser UAC Tyr UGC Cys C
U UUA Leu UCA Ser UAA Stop* UGA Stop* A
U UUG Leu UCG Ser UAG Stop* UGG Trp G
C CUU Leu CCU Pro CAU His CGU Arg U
C CUC Leu CCC Pro CAC His CGC Arg C
C CUA Leu CCA Pro CAA Gin CGA Arg A
C CUG Leu CCG Pro CAG Gln CGG Arg G
A AUU Ile ACU Thr AAU Asn AGU Ser U
A AUC Ile ACC Thr AAC Asn AGC Ser C
A AUA Ile ACA Thr AAA Lys AGA Arg A
A AUG Met** ACG Thr AAG Lys AGG Arg G
G GUU Val GCU Ala GAU Asp GGU Gly U
G GUC Val GCC Ala GAC Asp GGC Gly C
G GUA Val GCA Ala GAA Glu GGA Gly A
G GUG Val GCG Ala GAG Glu GGG Gly G
The codons are read in the 5´ → 3´ direction.
*Termination codons.
**AUG start codon.