engleski

Estimation of stability constants of mixed amino acid complexes with copper(II) from topological indices

Stability constants of binary and ternary complexes of five naturally occuring amino acids (Gly, Ala, Val, Phe, Tyr) with copper(II) were correlated with the Wiener's (W) and the valence connectivity indices (c) of their ML2 complexes yielding the correlation coefficient r = 0.931 - 0.997, and the root-mean-square (rms) deviation between measured and estimated values in the range of 0.013 to 0.065 log K units. Multiple regression of the 27 second ligation constants of binary and ternary complexes of 10 amino acids (Gly, Ala, Val, Leu, Ser, Thr, Met, Phe, Tyr, Trp) on topological indices of various molecular species (L, ML, ML2) yielded R= 0.696 - 0.756 and rms = 0.17 - 0.19 log K2 units. The result is essentially better than the results obtained by mechanistic method of M. Tabata and M. Tanaka (see Ref. 8) on the same set of data (rms = 0.39 log K2 units). The method appeared to be sensitive to ability of amino acid for additional (apical) coordination, but not very sensitive to other structural properties (aromacity, polarity). Among the models used, the best results were obtained with the third-order valence-connectivity index (3cv) calculated for the formula of complex compounds (ML and ML2).

stability constants; copper(II) chelates; topological indices.

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