[Exchange of A1-glycine in bovine insulin with L- and D-tryptophan]

Substitution of A1-glycine of insulin by L-amino acids yields in analogues with low biological activity. With D-amino acids in A1 biological activity is essentially retained. Synthesis of [A1-L-tryptophan]- and [A1-D-tryptophan]-insulin should provide information about the position of the side chains of L- and D-amino acids relative to A19-tyrosine, e.g. by evaluation of intramolecular resonance energy transfer between the fluorescent side chains. [A1-D-Tryptophan]-insulin exhibits full biological activity.