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Abstract— C18 formate ester (5) [2-(6-methyl-8-(2,6,6-trimethyl-1-cyclohexen-1-yl)-3E,5E,7E-octatrienyl formate], a highly reactive analog of retinal, was synthesized and its interaction with bacterioopsin studied. The formate ester, in the absence of purple or bleached membrane, undergoes very rapid reaction (tl/2 = 0.9 min) in neutral buffer but with membrane present it diffuses more rapidly into the membrane where it reacts slowly. Incorporation of 5 in the membrane results in a 38 nm (3900 cm-1 ) red shift which remains after reconstitution with retinal. Similar experiments with the corresponding C18 alcohol (4) results in a red shift, but this absorption blue shifts upon reconstitution with retinal. Washing the formate ester-treated membrane with bovine serum albumin or the corresponding lyophilized preparation with hexane, treatments that remove retinal oxime, fails to remove the UV-visible absorption, suggesting that a covalent bond between the C18 moiety and a nucleophilic group of the protein has probably formed. 相似文献
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Savukov IM Seltzer SJ Romalis MV 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2007,185(2):214-220
We demonstrate detection of proton NMR signals with a radio-frequency (rf) atomic magnetometer tuned to the NMR frequency of 62 kHz. High-frequency operation of the atomic magnetometer makes it relatively insensitive to ambient magnetic field noise. We obtain magnetic field sensitivity of 7 fT/Hz1/2 using only a thin aluminum shield. We also derive an expression for the fundamental sensitivity limit of a surface inductive pick-up coil as a function of frequency and find that an atomic rf magnetometer is intrinsically more sensitive than a coil of comparable size for frequencies below about 50 MHz. 相似文献
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We describe an alkali-metal magnetometer for detection of weak magnetic fields in the radio-frequency (rf) range. High sensitivity is achieved by tuning the Zeeman resonance of alkali atoms to the rf frequency and partially suppressing spin-exchange collisions in the alkali-metal vapor. We demonstrate magnetic field sensitivity of 2 fT/Hz(1/2) at a frequency of 99 kHz with a resonance width of 400 Hz. We also derive a simple analytic expression for the fundamental limit on the sensitivity of the rf magnetometer and show that a sensitivity of about 0.01 fT/Hz(1/2) can be achieved in a practical system with a measurement volume of 200 cm3. 相似文献
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Stanley Seltzer 《Photochemistry and photobiology》1999,70(4):680-685
The title compound (4) was synthesized in three steps from 1,1-dimethoxy-7-methyl-9-(2′,6′,6′-trimethyl-1-cy-clohexen-1-yl)-4E,6E,8E-nonatrien-3-one (1). Interaction of 4 with bacterioopsin produced a pigment absorbing at 573 nm, which, on long standing in the dark, moves to 406 nm, mirroring the behavior of nonradioactive 4 with bacterioopsin (S. Seltzer, J. Org. Chem. 60, 1189–1194, 1993). Compound 4 was designed to test for the involvement of a nucleophilic side chain, presumably asp-212, in catalyzing the dark cis-trans isomerization of bound retinal, through its attack at C-13. Such a mechanism is anticipated to lead to a cross-linked product where the nucleophile replaces the 13-acetoxy group when 4 is substituted for the natural chromophore. The protein, reconstituted with 4, after extensive washing, solubilization in dimethylsulfoxide and extensive dialysis retains its radioactivity suggesting the establishment of a cross-link. Solution in 6 M urea, however, results in substantial loss of radioactivity, suggesting that the unfolded labeled protein suffers hydrolysis of the very labile 13-enolester group followed by proton exchange. 相似文献
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Seltzer SJ Michalak DJ Donaldson MH Balabas MV Barber SK Bernasek SL Bouchiat MA Hexemer A Hibberd AM Kimball DF Jaye C Karaulanov T Narducci FA Rangwala SA Robinson HG Shmakov AK Voronov DL Yashchuk VV Pines A Budker D 《The Journal of chemical physics》2010,133(14):144703
Many technologies based on cells containing alkali-metal atomic vapor benefit from the use of antirelaxation surface coatings in order to preserve atomic spin polarization. In particular, paraffin has been used for this purpose for several decades and has been demonstrated to allow an atom to experience up to 10?000 collisions with the walls of its container without depolarizing, but the details of its operation remain poorly understood. We apply modern surface and bulk techniques to the study of paraffin coatings in order to characterize the properties that enable the effective preservation of alkali spin polarization. These methods include Fourier transform infrared spectroscopy, differential scanning calorimetry, atomic force microscopy, near-edge x-ray absorption fine structure spectroscopy, and x-ray photoelectron spectroscopy. We also compare the light-induced atomic desorption yields of several different paraffin materials. Experimental results include the determination that crystallinity of the coating material is unnecessary, and the detection of C[Double Bond]C double bonds present within a particular class of effective paraffin coatings. Further study should lead to the development of more robust paraffin antirelaxation coatings, as well as the design and synthesis of new classes of coating materials. 相似文献
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W. Potzel F. E. Wagner R. L. Mössbauer G. Kaindl H. E. Seltzer 《Zeitschrift für Physik A Hadrons and Nuclei》1971,241(2):179-187
The recoilless nuclear gamma resonance of the 127 keV γ-rays of101Ru was observed in ruthenium metal, RuO2 and [Ru(NH3)4(HSO3)2]. By comparison of the isomer shifts observed in these materials for the 127 keV absorption line with the corresponding shifts of the 90keV γ-rays of99Ru one obtains δ〈r 2〉 [127 keV]/ δ〈r 2〉 [90 keV]=1.78±0.26 for the ratio of the changes of the mean square nuclear charge radii between the first excited and the ground states in these nuclei. An estimate of electron density differences based on free-ion relativistic self-consistent field calculations yields δ〈r 2〉[90keV]≈+1.4·10?3 for99Ru and δ〈r 2〉/〈r 2〉 [127 keV]≈+2.4·10?3 for the101Ru case. These results are discussed in terms of the core excitation model. 相似文献
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The perturbation theory of the electromagnetic and weak interactions is considered in the framework of nonlocal theory. A hypothesis is proposed that the photon and neutrino fields are connected with the charged local fields of the electrons, muons, and W bosons in the nonlocal way.The definite intermediate regularization procedure is introduced that the S matrix is finite, unitary, causal, gauge invariant in perturbation theory when regularization is moved off. The interaction Lagrangian contains no infinite counter terms and the S matrix is finite without any infinite renormalizations. 相似文献