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Biomedical subjects

W J Caspary

Publications and source records attributed to W J Caspary.

4 recordsLinked to original sources
PubMed1978

Studies on spin labeled ribonucleic acids encapsulated by viral proteins.

Spin labeled poly rA (sl-poly rA) was encapsulated by the coat proteins of two plant viruses having different morphologies: TMV, a rigid rod and CCMV, an icosahedral sphere. Electron microscopy showed that the resultant particles were morphologically similar to the parent virus from which the coat protein was obtained. Encapsulation produced progressive immobilization of the spin label. The motion of the spin label attached to TMV-sl-poly rA appears anisotropic with a correlation time about the long axis of approximately 5 x 10(-6) sec. Exogenous nuclease had no effect on the epr spectrum of this nucleo-protein complex. The epr spectrum of CCMV-sl-poly rA was isotropic with a correlation time less than 5 x 10(-7). CCMV-sl-poly rA was partially degraded by T2 ribonuclease. Theoretical calculations of correlation times for the motion of the nucleo-protein particles were similar to the experimentally derived values suggesting that the nucleo-protein particles are tightly packed with little potential for internal motion.

Electron Spin Resonance Spectroscopy↗
PubMed1976

Spin labeled nucleic acids.

Homopolyribonucleotides and E. coli DNA wer spin labeled with an iodoacetamide-nitroxide compound. The extent of labeling is highly dependent upon the nature of the base and the secondary structure of the nucleic acid. This spin label-polymer linkage is unstable at high temperatures and in phosphate buffers. In order to determine the effect of changes in the environment of nucleic acids on the esr signals of their attached spin labels, the polynucleotides were subjected to temperature and viscosity perturbations. An increase in temperature (T) affects a linear decrease in the anisotropy factor of the esr signal. The log tau (tau = correlation time) versus (1/T) profile is linear with a positive slope when the spin label is attached to single stranded polynucleotides but exhibits discontinuities at certain critical temperatures when attached to the duplexes poly (As-U) and poly (I-Cs). These critical temperatures are lower than the optical Tm. Logarithmic increase in viscosity was found to produce a linear increase in tau in aqueous sucrose solutions.

Binding Sites↗