Relative Silver(I) Ion Binding Energies of a- Amino Acids: A Determination by Means of the Kinetic Method

The relative silver(I) ion binding energies of 19 a-amino acids have been measured by means of the kinetic method. In general, they are similar to the relative copper(I) ion binding energies of corresponding amino acids although there are differences that can be accounted for by differences in silver(I) and copper(I) chemistry. The correlation with proton basicities is comparatively poorer. Again, the differences between silver(I) and proton binding can be attributed to differences in silver(I) and proton chemistry. The relative silver(I) binding energies measured are best described as relative basicities or DDG°Ag’s. The observed internal consistency during construction of a silver(I) ion basicity ladder implies that DDS°Ag is approximately zero except when histidine and lysine are involved. For 16 a-amino acids, their relative silver(I) ion basicities ' relative silver(I) ion affinities or DDG°Ag ' DDH °Ag. (J Am Soc Mass Spectrom 1998, 9, 760–766) © 1998 American Society for Mass Spectrometry The bio-inorganic chemistry of the silver(I) ion isrich and fascinating. The silver(I) ion has longbeen used as a bactericide in the form of eye drops for newborns [1, 2]. Some of its complexes display remarkable antimicrobial activities [3, 4]. The metallothioneins, a class of small proteins believed to b