the three aromatic amino acids , phenylalanine , tryptophan , and tyrosine , the charged hydrophilic amino acids , aspartic acid and lysine , and the neutral amino acid alanine were found to occur most often in the determinant region of the peptides tested , whereas asparagine , cysteine , and histidine occurred the least often .
C0002520
amino acids
C0301715
neutral amino acid