Formation constants of silver(I) complexes of some sulphur-containing dipeptides and valylvaline

Abstract

Formation constants at 25 °C and I= 0.10 mol dm ^–3(KNO₃) have been determined for the complexes of Ag^I with a range of nine dipeptides which incorporate side-chains containing one (glycylmethionine and methionylglycine) or two sulphur donor atoms. In the latter case dipeptides formed from amino acids of the same and of different chiralities were studied (e.g. L-methionyl-L-methionine and L-methionyl-D-methionine). The results are compared with those for valylvaline. Values for the formation constants are interpreted in terms of the preferred conformations of the dipeptides, and the tendency for Ag^I to bond to S-donor atoms or to adopt linear co-ordination through the formation of dimeric complexes.