PREDICTING RELATIVE TOXICITY AND INTERACTIONS OF DIVALENT METAL-IONS - MICROTOX(R) BIOLUMINESCENCE ASSAY

Both relative toxicity and interactions between paired metal ions were predicted with least-squares linear regression and various ion charac teristics. Microtox(R) 15 min EC50s (expressed as free ion) for Ca(II) , Cd(II), Cu(II), Hg(II), Mg(II), Mn(II), Ni(II), Pb(II), and Zn(II) w ere most effectively modeled with the constant for the first hydrolysi s (K-H for M(n+) + H2O --> MOH(n-1) + H+) although other ion character istics were also significant in regression models. The \log K-H\ is co rrelated with metal ion affinity to intermediate ligands such as many biochemical functional groups with O donor atoms. Further, ordination of metals according to ion characteristics, e.g., \log K-H\, facilitat ed prediction of paired metal interactions. Pairing metals with strong tendencies to complex with intermediate or soft ligands such as those with O or S donor atoms resulted in strong interactions.