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121.
Michael Caffrey Joshua Kaufman Stephen J. Stahl Paul T. Wingfield Angela M. Gronenborn G.Marius Clore 《Journal of magnetic resonance (San Diego, Calif. : 1997)》1998,135(2):368-372
A suite of 3D NMR experiments for measuring15N–{1H} NOE,15NT1, and15NT1ρvalues in large proteins, uniformly labeled with15N and13C, is presented. These experiments are designed for proteins that exhibit extensive spectral overlap in the 2D1H–15N HSQC spectrum. The pulse sequences are readily applicable to perdeuterated samples, which increases the spectral resolution and signal-to-noise ratio, thereby permitting the characterization of protein dynamics to be extended to larger protein systems. Application of the pulse sequences is demonstrated on a perdeuterated13C/15N-labeled sample of the 44 kDa ectodomain of SIV gp41. 相似文献
122.
Iwaniszewski J Kaufman IK McClintock PV McKane AJ 《Physical review. E, Statistical physics, plasmas, fluids, and related interdisciplinary topics》2000,61(2):1170-1175
Electronic analog experiments on escape over a fluctuating potential barrier are performed for the case when the fluctuations are caused by Ornstein-Uhlenbeck noise (OUN). In its dependence on the relation between the two OUN parameters (the correlation time tau and noise strength Q) the nonmonotonic variation of the mean escape time T as a function of tau can exhibit either a minimum (resonant activation), or a maximum (inhibition of activation), or both these effects. The possible resonant nature of these features is discussed. We claim that T is not a good quantity to describe the resonancelike character of the problem. Independently of the specific relation between the OUN parameters, the resonance manifests itself as a maximal lowering of the potential barrier during the escape event, and it appears for tau of the order of the relaxation time toward the metastable state. 相似文献
123.
A series of nonpolar single- and two-ring dipentyl derivatives of p-carboranes, bicyclo[2.2.2]-octane and benzene was investigated in the pure state and in binary mixtures with a nematic host. The resulting virtual nematic-isotropic transition temperatures [TNI] for single ring compounds were compared with those for two ring compounds. All [TNI] were compared with the molecular aspect ratios X and filling fractions F obtained from MNDO calculations. The highest effectiveness in promotion of the nematic phase was found for bicyclo[2.2.2]octane and 12-vertex p-carborane and ascribed to exceptional molecular rigidity and electronic properties, respectively. Results show that a high filling fraction F and molecular stiffness are the necessary factors for a highly stable nematic phase. 相似文献
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A theory of whistler wave leakage from a magnetic field aligned duct with enhanced plasma density is presented. The energy flux from the duct and the corresponding wave attenuation rate are calculated in the WKB approximation. Possible experimental confirmations of the theory are indicated. 相似文献
127.
Mordechai Deutsch Reuven Tirosh Menachem Kaufman Naomi Zurgil Arye Weinreb 《Journal of fluorescence》2002,12(1):25-44
The use of fluorescence polarization as a functional parameter in monitoring cellular activation calls for the reliable and accurate measurement of the fluorescence intensity and polarization (FI and FP) of microscopic objects. The relevant experimental parameters that enter such measurements are thoroughly discussed. The possibility of executing FP measurements properly by flow-through systems is compared with that of static cytometry. Remarks on the effects of high-power excitation on markers and cells conclude the paper. 相似文献
128.
K. Dorenburg H. -J. Glas S. L. Kaufman G. zu Putlitz 《Zeitschrift für Physik A Hadrons and Nuclei》1974,267(4):257-259
An optical pumping experiment was performed to obtain precise hfs shifts for Cs in Argon. The shifts measured include a term quadratic in the densityρ and a large temperature coefficient. The coefficients of the expansionδv/v 0=a ρ+bρ 2 area(80 °C)=?29.8(6)x10?9(Torr?1(0°C))b(80 °C)=+11(2)x10?14(Torr?2(0 °C)). The shift grows more negative with increasing temperature by 0.37 (2)%/°C. 相似文献
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