Biomedical subjects
Publications and source records attributed to W Snipes.
Spin labels dissolved in highly purified fatty acid systems exhibit nearly identical tumbling rates in liquid and solid phases. Even though the spin labels do not have the same molecular geometry as the lipid matrix the melting point of the matrix can be inferred by measurements of the temperature dependency of molecular motion.
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Bases, nucleosides, nucleotides, and polynucleotides were exposed to chemically generated singlet oxygen to determine whether the species oxidized paralleled those oxidized in photodynamic reactions. In neutral or basic aqueous solution guanine, guanosine, deoxyguanosine, guanylic acid, deoxyguanylic acid, thymine, and uracil reacted with singlet oxygen. Since these compounds are oxidized in photodynamic processes, this study provides further evidence that singlet oxygen is the active intermediate in the photodynamic oxidation of nucleic acid constituents. Dienophilic attack by singlet oxygen is considered to be a plausible mechanism in these reactions.
Spin-label studies were carried out on Neurospora mitochondria under in vivo and in vitro labeling conditions. A long-chained spin-labeled fatty acid was incorporated by Neurospora and was found in mitochondrial phospholipids. The molecular motion at various temperatures was different from that for the same spin label under in vitro labeling conditions. The results for spin-labeled mitochondria were compared with those from isolated lipids and with those from aggregates of spin-labeled fatty acid and isolated bovine serum albumin. These comparisons suggest that the hydrocarbon portions of membranes are relatively fluid and are not extensively restricted in motion by association with proteins.
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The rate of free radical decay was measured at various temperatures using electron paramagnetic resonance spectroscopy. Rate constants determined from first-order decay kinetics were used to determine the activation energy for the process of free radical decay. The similarity between the temperature dependence of free radical decay by heat and that of electrical conductivity has led us to consider the possibility that the two processes may be related. Mechanisms by which a population of electron-hole conducting states may lead to free radical decay are outlined and experimental data relating to these mechanisms are discussed.