Biological methane activation involves the intermediacy of carbon-centered radicals.

The spin-trapping technique has demonstrated that carbon-centered radicals are produced during soluble-methane-monooxygenase catalysis of the hydroxylation of several different types of substrate. The resulting spin-adducts were identified from the hyperfine splitting constants in their EPR spectra. Isotopic labelling showed unequivocally that the trapped radicals were derived from substrate. The carbon-centered substrate radicals are believed to result from hydrogen-atom abstraction by a ferryl species in a cytochrome-P-450-like mechanism. No hydroxy radical nor an oxygen-based radical of any kind was detected in any of the spin-trapping experiments.     

Identification of an interleukin-1 beta binding protein in human plasma

A covalent cross-linking technique was used to bind iodinated interleukin-1 (IL1) alpha and beta to plasma proteins. One specific IL1 beta binding protein was observed, that when cross-linked to ¹²⁵I-ILl beta migrated to approximately 60 kDa on SDS-PAGE. The protein did not bind IL1 alpha. The 43 -kDa protein was partially purified using a wheat germ agglutinin affinity column. The isolated factor again specifically bound IL1 beta, and appeared to consist of single chain glycoprotein. The protein was heat stable and had a rapid association time with IL1 beta. This protein may be an important carrier molecule for IL1 beta in vivo.     

Book Reviews

Radicals in Organic Synthesis: Formation of Carbon-Carbon Bonds by Bernd Giese (Pergamon Press, 1986)

Metabolism and Action of Anti-Cancer Drugs G. Powis and R.A. Prough (Eds.) Taylor & Francis: London 1987. ISBN 0-85066-3695     

Formation of Radicals by Mechanical Processes

The application of e.s.r. spectroscopy to the study of radicals formed by mechanical means (grinding, shearing, bending, cutting, etc.) is discussed. Two mechanisms are considered, one being the homolytic breaking of main-chain bonds in polymers, and the other being charge-transfer (tribo-electric effect). The former is thought to occur for high polymers whilst the latter may be important for certain inorganic materials especially ionic solids.

Specific examples are given for the generation of radicals by cutting finger nails and by grinding bone. In both cases, well-defined e.s.r. spectra were obtained for which identifications are offered. Possible implications of the mechanical formation of radicals in bone are considered.     

Responses of cultured rat trigeminal ganglion neurons to bitter tastants

The initial steps in taste and olfaction result from the activation by chemical stimuli of taste receptor cells (TRCs) and olfactory receptor neurons (ORNs). In parallel with these two pathways is the chemosensitive trigeminal pathway whose neurons terminate in the oral and nasal cavities and which are activated by many of the same chemical stimuli that activate TRCs and ORNs. In a recent single unit study we investigated the responses of rat chorda tympani and glossopharnygeal neurons to a variety of bitter-tasting alkaloids, including nicotine, yohimbine, quinine, strychnine and caffeine, as well as capsaicin, the pungent ingredient in hot pepper. Here we apply many of these same compounds to cultured rat trigeminal ganglion (TG) neurons and measure changes in intracellular calcium [Ca2+]i to determine whether TG neurons will respond to these same compounds. Of the 89 neurons tested, 34% responded to 1 mM nicotine, 7% to 1 mM caffeine, 5% to 1 mM denatonium benzoate, 22% to 1 mM quinine hydrochloride, 18% to 1 mM strychnine and 55% to 1 microM capsaicin. These data suggest that neurons from the TG respond to the same bitter-tasting chemical stimuli as do TRCs and are likely to contribute information sent to the higher CNS regarding the perception of bitter/irritating chemical stimuli.