ABSTRACT
Concurrent with emerging world-wide use of diverse organotins as industrial biocides, catalysts, and plastics stabilizers have grown highly sophisticated analytical methods permitting their ultratrace (<ppb) molecular speciation in both environmental and biological media. These characterization advances have been achieved in large part because of newly available very selective chromatographic substrates — operating either in liquid or gas modes — directly coupled with sensitive tin-selective detectors capable of quantitating the element below picogram levels. At the foundation of this present state of measurement is the remarkable stability and longevity of the tin-carbon sigma bond, which by both numbers and kinds of covalently bound organic groups confers sufficient chemical information for precise and quantitative isolation and determination. The same architectural features in the tin-carbon skeleton encode vital information dictating biological activity. Thus, we can now show that quantitative topological treatment of organotins in terms of Sn-C bonding parameters and conformational variations conferred by local solvent or site complexation can predict membrane uptake and cellular metabolic response to a notable degree with bacteria, algae, and larvae. Now and in the future, our arsenal of speciation methods and quantitative structure-activity relationships derived from key organotin moieties must be directed to assessments of specific cellular and subcellular toxic or benign responses. Among current research options are both the evaluation of homologies of nonlabile functions bound to tin, its coordination number and oxidation state, and its local site stereo-chemistry as also influenced by labile neutral or charged ligands. From such considerations, we construct a picture of reasonable cellular sites and transport agents for bioactive tin-containing molecules relevant to the concerns of this symposium.
