No abstract

These data suggest that at 77 K the methyl radicals rotate about an axis perpendicular to the planes of the radical, whereas the ethyl radical rotates about the C-C bond axis. The analysis of spectra from allyl and methallyl radicals is less conclusive.

Riboflavin and FAD (flavin-adenine-diucleotide) were obtained from Cal. Biochem. Co., Los Angeles, California. FMN (flavin-mono-nucleotide) was donated by Eisai Pharmacy Co., Tokyo, Japan. The estimated purity of these compounds was better than 95 per cent. D-amino acid oxidase was prepared by the method of Kubo et a/.@) and further purified with calcium phosphate gel and Sephadex G-100. MATERIALS A N D METHOD ApparatusThe EPR spectrometer used was a Varian V-4502 with associated 9-in. magnet power supply. Recordings were made on a Moseley Model 2D recorder. The spectrophotometer used was a Bausch and Lomb Spectronic 505 for determinations of flavin concentrations. The U.V. light source was a PEK 200 watt, high pressure mercury lamp, powered

ESR spectra of the methyl, ethyl, n-propyl and allyl radicals adsorbed on silica gel were analysed in terms of g-factor and hyperfine coupling anisotropies. The magnitudes of the anisotropies demonstrate that at 4 K the methyl radical reorients about its threefold axis, and the ethyl radical reorients about the C -C-bond axis. The experimental data for the methyl and ethyl radicals have been combined to yield the dipolar hyperfine coupling for an α-proton. The constants thus derived are B