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31.
Voltage-dependent outward current measured in the dark is reduced after illumination. This reduction can be blocked by tetraethylammonium and is associated with a decrease in total membrane conductance. The voltage dependence of the current reduced by light is the same as that of the delayed rectifier. These results indicate that light modulates the delayed rectifier. This modulation serves to maintain a stable voltage response to constant illumination. 相似文献
32.
Cytokinin from soluble RNA of Escherichia coli: 6-(3-methyl-2-butenylamino)-2-methylthio-9-beta-D-ribofuranosylpurine 总被引:12,自引:0,他引:12
W J Burrows D J Armstrong F Skoog S M Hecht J T Boyle N J Leonard J Occolowitz 《Science (New York, N.Y.)》1968,161(842):691-693
We have isolated a compound responsible for the cytokinin activity of soluble RNA from Escherichia coli. The structure, indicated as 6-(3-methyl-2-butenylamino)-2-methylthio-9-beta-D-ribofuranosylpurine, C(16)H(23)N(5)0(4)S, on the basis of low-and high-reso!ution mass spectrometry, was established by unequivocal synthesis. The mass spectra, chromatographic behavior, and ultraviolet spectra of the compounds from natural and synthetic sources were identical. 相似文献
33.
A fluorescent modification of adenosine triphosphate with activity in enzyme systems: 1,N 6 -ethenoadenosine triphosphate 总被引:3,自引:0,他引:3
A new, highly fluorescent adenosine triphophate (ATP) analog, 1,N(6) ethenoadenosine triphosphate, has been synthesized. Its fluorescence properties, including the long fluorescence lifetime and the possibility of detection at very low concentrations, in conjunction with its activity in the representative enzyme systems here reported, make it a valuable probe of enzymic mechanism and structure. 相似文献
34.
The formyl cation, HCO+, has long been believed to be an important intermediate in the chemistry of carbon monoxide (CO) in acidic environments, but its spectroscopic observation in solution has been elusive. This species was generated by the reaction of CO with the liquid superacid hydrofluoric acid-antimony pentafluoride (HF-SbF5) under pressure and was observed by nuclear magnetic resonance and infrared spectroscopy. Equilibria between CO in the gas phase, CO dissolved in HF-SbF5, the SbF5 adduct of formyl fluoride, and HCO+ associated with several equilibrating anions of the type [SbxF5x+1]- are proposed to describe the system. 相似文献
35.
Flavell RA Kaczmarek LK Badou A Boulpaep EL Desai R Basavappa S Matza D Peng YQ Mehal WZ 《Science (New York, N.Y.)》2005,310(5756):1903
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Sir2 (silent information regulator 2) is a nicotinamide adenine dinucleotide-dependent deacetylase required for longevity due to calorie restriction in yeast and Drosophila. In mammals, calorie restriction induces a complex pattern of physiological and behavioral changes. Here we report that the mammalian Sir2 ortholog, Sirt1, is required for the induction of a phenotype by calorie restriction in mice. 相似文献
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