Biomedical subjects
Publications and source records attributed to Russell J Pearson.
Two diastereoisomeric cycloadducts are capable of accelerating their own formation through the assembly of catalytic ternary complexes. The two cycloadducts do not have any measurable catalytic effect on the rate of formation of their diastereoisomer. [structure: see text]
Covalent modifiers of proteins are of importance in chemical proteomics, an emerging chemical technology used to assign protein function. In this study, high-field (1)H NMR techniques were used to analyze the reaction of the bioactive compound, 2,3-bis(bromomethyl)quinoxaline 1,4-dioxide, with amines (a model system for proteins containing nitrogen-based nucleophiles). Unexpectedly, the results show that a double nucleophilic substitution reaction involving 2 equiv of the amine is preferred to an intramolecular cyclization pathway. A direct comparison with the reaction carried out on a substrate lacking the N-oxide functional groups is also provided. X-ray crystal structures and computational studies are used to rationalize the observed differences in reactivity between the two systems.
The rate of reaction and the selectivity of a Diels-Alder cycloaddition between a furan and a maleimide can be enhanced by the introduction of complementary recognition sites on the reactant species. Subtle manipulation of other structural elements allows the generation of the observed rate enhancements and selectivities through either self-replication or formation of a pre-reactive binary complex.
Nitric oxide (NO) is produced continuously from the endothelium and plays a pivotal role in the control of vascular tone. Many of the current therapeutic agents that increase blood flow through production of NO have to be taken orally and can produce significant adverse side effects. We now report on some novel NO-donor drugs, based on thiosugars that generate NO spontaneously. From the range of compounds synthesized, D-SNAG ( S -nitroso-1-thio-2,3,4,6-tetra- O -acetyl-beta-D-glucopyranose) was as effective a vasodilator as any other and, as it was the easiest to synthesize, we undertook a more detailed evaluation to understand the chemistry and mode of action of its vasodilator effect. From the chemical kinetic data, we found that NO release occurred predominantly by thermal decomposition, with a 20-fold increase in decomposition rate between 19 and 37 degrees C. In the forearm of eight normal male subjects, we found that D-SNAG produced a significant dose-dependent vasodilator effect ( P =0.001) with good reproducibility (19%) on repeated testing. We propose that delivery of NO from D-SNAG to the forearm skin microvessels most probably occurs by diffusion across the epidermis. Since such compounds release NO in a non-enzymic manner following topical application, they might produce an attractive therapeutic source of localized NO delivery without inducing systemic side effects.