COMPLEX FORMATION BETWEEN HEAVY METALS AND THIOLACETIC ACID IN ELECTRON MICROSCOPIC HISTOCHEMISTRY

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Abstract
Evidence for the formations of complexes of aurous and lead ions with thiolacetic acid was obtained by two methods. (1) It was demonstrated that the addition of the metal ions to solutions of thiolacetic acid at pH 6.2 caused a bathochromic shift of the ultraviolet spectrum of this compound characteristic of those observed on combination of metal ions with an organic resonator. The experiments indicated that aurous ions form a coordinate complex with thiolacetic acid containing one metal ion and two thiolacetate residues. (2) It was observed that aurous and lead ions inhibited the reaction of thiolacetic acid with N-ethylmaleimide. Complex formation of the heavy metals with thiolacetic acid may be of importance in preventing their binding at nonspecific sites and in facilitating their penetration into tissue sections in the adaptation for electron microscopy of the thiolacetic acid method for cholinesterases.