No abstract

With the objective to understand how the pattern and degree of chlorination influence on the properties of the title molecules, a computational study on biphenyl and all the chlorinated biphenyls (from 1 to 10 chlorine atoms, 209 congeners) has been undertaken. The study includes conformational searches (and further refinement by molecular dynamics simulations) and the ab initio calculation of the molecular electrostatic potential (MEP) and the dipole moments for all the congeners. The most significant property is the MEP, finding a good correlation between the MEPs and the substitution pattern on chlorinated biphenyls. The most toxic congeners possess highly positive values of electrostatic potential on the aromatic rings and highly negative values of electrostatic potential on the chlorine atoms. Additionally, we have found that the toxic congeners possess conformations with low dipole moments, a fact that may be linked to the ready accumulation on the adipose tissue. The results on the geometry and electrostatic properties of chlorinated biphenyls can be useful to rationalize their selective toxicities.

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The function of conventional immuno-logical assays is to determine the presence and amount of known substances. Cross-reactivity of antibodies with unknown species of similar structure is a problem that can be circumvented by using chromatography in a second level of discrimination. Tandem LC-IA systems increase the selectivity and the sensitivity of assays by removing interfering species. For cases in which the goal is to prove that similar species are absent from a sample or to identify antigen variants, conventional assays fail. LC-IA systems are adept at dealing with these tasks. The necessary steps of metering reagents, separating Ag:Ab complex from other species, and enhancing detection in an immunological assay are easily accommodated by the LC system. In fact, the LC system provides a wide variety of new, high-sensitivity, high-speed methods for carrying out immunological assays. On the basis of the enormous versatility, selectivity, and sensitivity that LC-IA brings to analytical chemistry, we believe this technique will become increasingly important for monitoring analytes in complex biological matrices.