Decay rates biological compounds

As pointed out by these workers [147], the rates of release of ATP or other biological substrates are generally deduced indirectly and are frequently inferred solely from the decay rate of aci-nitro anion intermediates (44), which absorb in the near-UV. Such analyses can sometimes be complicated by non singleexponential kinetics that may be the result of overlapping bands from other byproducts of photolysis. As nicely demonstrated [147], structurally more informative TRIR experiments can not only monitor directly the kinetics of release of the biological compound of interest but also provide valuable information concerning the identities and chemical fates of byproducts. 

In addition to its quantitative aspects, adsorptive stripping voltammetry provides important contributions to our knowledge of biological compounds. In particular, considerable recent activity in our laboratory has focussed on the achievement of direct electron traiisfer for various biomacromolecules. The strategy here is to form the protein/-electrode complex , essential for a facile redox process, using an unmodified electrode. Electron-transfer rates are known to decay rapidly (exponentially) upon increasing the distance between the electrode and the redox center of the biomacromolecule. Binding of such molecules to the surface may thus be effective for electron-transfer enhancement. Other laboratories have concentrated on the use of electrode modifiers (e.g.,... 

Chemical/Physical. Hydrolysis in distilled water at 25 °C produced 3-chloro-2-propen-l-ol and HCl. The reported half-life for this reaction is only 2 d (Kollig, 1993 Milano et al., 1988). trans-1,3-Dichloropropylene was reported to hydrolyze to 3-chloro-2-propen-l-ol and can be biologically oxidized to 3-chloropropenoic acid which is oxidized to formylacetic acid. Decarboxylation of this compound yields carbon dioxide (Connors et al., 1990). Kim et al. (2003) reported that the disappearance of tra 35-l,3-dichloropropylene in water followed a first-order decay model. At 25 and 35 °C, the first-order rate constants were 0.083 and 0.321/d, respectively. The corresponding hydrolysis half-lives were 8.3 and 2.2 d, respectively. 

Manganese compounds of biologic importance are examined by pulse radiolysis e.g., the rate of dismutation of radiation-generated Of is catalyzed by Escherichia coli, Mn-containing superoxide dismutase involving electron transfer in which enzymes with Mn(IV), Mn(IIl), Mn(II) and Mn(I) oxidation states are involved. A kinetic model for the reaction mechanism of an Mn dismutase from Bacillus stearothermophilus accounts for the variation of the rate of decay on the concentrations of Oj, enzyme, HjOj, NaNj, KCN and H+. 

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