nucleotidyl- ( 5 ' leads to n ) -amino acids containing different heterocycle bases : adenine , guanine , hypoxanthine , cytosine , uracyl , and aromatic amino acids : phenylalanine , tyrosine and tryptophan , have been investigated by proton magnetic resonance and circular dichroism .
C0301713
aromatic amino acids
C0031453
phenylalanine