Ian C. P. Smith

An electron spin resonance study of proton transfer equilibria involving the semiquinone radicals derived from hydroquinone and catechol

The electron spin resonance spectra of the semiquinone radicals derived from hydroquinone and catechol have been studied in aqueous solutions of varying ph in a rapid flow system. The spectra were found to change drastically with ph; these effects are attributed to protonation of the semiquinones at rates which are dependent on the ph. Models for the systems are proposed, and the effects of exchange are described by means of the modified Bloch equations. Estimates are made of the rate constants and equilibrium constants for protonation of the semiquinone radicals and limits are set for the rate of hydroxyl proton exchange between the radical species and solvent in the low ph region.

Proton Magnetic Resonance of Transfer RNA

The temperature dependence of the areas under the proton magnetic resonance spectra of unfractionated yeast transfer RNA in 1.0 molar NaCl is a consequence of salt-induced aggregation and does not constitute a monitor of the melting of secondary molecular structure. Such melting can be observed by following the widths of the resonances in the various regions of the spectra. Peaks attributable to dihydrouracil and the methyl groups of the methylated bases are detected in the spectra of unfractionated transfer RNA and alanine transfer RNA.