Quantitative studies of the avidity of naturally occurring substances for trace metals. 2. Amino-acids having three ionizing groups

Abstract

The avidities of alpha-amino-acids with 3 ionizing groups for the ions of heavy metals were measured and recorded as stability constants. For any 1 metal the stability constants varied over an enormous range (e.g. by 10ll for Ni). However, the order of avidities for any given amino acid, remains as with glycine. Tyrosine, ornithine, lysine, arginine, aspartic acid and glutamic acid were found to combine through the alpha-amino and alpha.carboxyl groups, after the manner of glycine. Other acids combine through the alpha and the omega N atoms (the S atom in cysteine). The homologous series: lysine, ornithine, alpha, gamma-diaminobutyric acid and alpha beta-diaminopropionic acid was examined and found to yield examples of transition between these 2 extremes. Several acids show abnormalities of behavior with Cu; cysteine and histidine show anomalies with Co, but histamine does not. The ionization constants of alpha, gamma-diaminobutyric, alpha, beta-diaminopropionic and benzoylglutamic acids were detd. for the 1st time.