Shot noise in mesoscopic systems

This is a review of shot noise, the time-dependent fluctuations in the electrical current due to the discreteness of the electron charge, in small conductors. The shot-noise power can be smaller than that of a Poisson process as a result of correlations in the electron transmission imposed by the Pauli principle. This suppression takes on simple universal values in a symmetric double-barrier junction (suppression factor 1/2), a disordered metal (factor 1/3), and a chaotic cavity (factor 1/4). Loss of phase coherence has no effect on this shot-noise suppression, while thermalization of the electrons due to electron-electron scattering increases the shot noise slightly. Sub-Poissonian shot noise has been observed experimentally. So far unobserved phenomena involve the interplay of shot noise with the Aharonov-Bohm effect, Andreev reflection, and the fractional quantum Hall effect.Comment: 37 pages, Latex, 10 figures (eps). To be published in "Mesoscopic Electron Transport," edited by L. P. Kouwenhoven, G. Schoen, and L. L. Sohn, NATO ASI Series E (Kluwer Academic Publishing, Dordrecht

Affinity modification of the membrane-bound microsomal cytochrome P-450 by substrate lipophilic analogs

The following lipophilic spin-labeled cytochrome P-450 analogs were synthesized: 2-octyl-4-(3-iodine-2-oxopropylidene)-2,3,5,5-tetramethylimidaz olidine-1-oxyl (RIII), 2-nonyl-4-(3-iodine-2-oxopropylidene)-2,3,5,5-tetramethylimidaz olidine-1-oxyl (RIV), 2-hepta-decyl-4-(3-iodine-2-oxopropylidene)-2,3,5,5-tetramethyl imidazolidine-1- oxyl (RV). The distribution coefficients, k, in water--lipid and water--octanol systems as well as the theoretical estimates of k for these and previously synthesized analogs, i.e., 4-(3-iodine-2-oxo-propylidenyl)-2,2,3,5,5-pentamethylimidazolid ine-1-oxyl (RI) and 2-hexyl-4-(3-iodine-2-oxopropylidene)-2,3,5,5-tetramethylimidaz olidine- 1-oxyl (RII) were determined. It was shown that RIII and RIV bind as type I substrates to cytochrome P-450 from rat microsomes induced with phenobarbital or 3-methylcholanthrene as well as to those from control rats. Radicals RIII and RIV inhibit the oxidation of aniline, aminopyrine and benzphetamine. RIII-RV strongly inhibit the O-deethylation of 7-etoxyresorufin. The inhibitory activity of the radicals increases in the following order: RV less than RIV less than or equal to RI less than or equal to RIII less than RII. The experimental results suggest that the inhibitory properties are nonmonotonuesly related to the lipophility. The high lipophility of RIII and its strong inhibitory properties permit to render the latter to the class of inhibitors which can be transported by liposome membrane vehicles to the liver, inhibit the in vivo activity of the microsomal system and thus prolong the effects of drugs oxidized by cytochrome P-450