共查询到20条相似文献,搜索用时 15 毫秒
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C. T. LIN Y. G. CHYAN G. C. KRESHECK HERBERT C. BITTING JR M. A. EL-SAYED 《Photochemistry and photobiology》1989,49(5):641-648
Several spectroscopic techniques (absorption, emission, transient absorption and differential scanning calorimetry--DSC) were used to investigate the deprotonation of dibucaine.HCl in a hydrophobic environment, and the interaction sites and mechanisms of the local anesthetic dibucaine.HCl on bacteriorhodopsin (bR) in purple membrane. The important results are summarized as follows: (1) the visible absorption features of native (lambda max = 568 nm) and deionized (lambda max = 608 nm) bR are sensitive to the amount of dibucaine.HCl added; (2) the emission spectrum of dibucaine.HCl embedded in the retinal-free mutant bR is similar to that of dibucaine free base in Triton X-100 micellar solutions; (3) the phosphorescence emission of dibucaine at 77 K is completely quenched by bR and the fluorescence quenching rate for the incorporated dibucaine.HCl in bR was determined as kq = 4.09 x 10(13) M-1 s-1; (4) the incorporation of dibucaine.HCl in bR inhibits the slow component rate of formation of M412 and decreases the amount of M412 formation in the photochemical cycle of bR; and (5) the thermal stability of native bR was measured by DSC in the presence and absence of dibucaine and yielded an endothermic transition at 95.9 +/- 1.0 degrees C with 13.6 J/g (3.25 +/- 0.12 cal/g) of enthalpy changes. All observations suggest that the action site of the local anesthetic, dibucaine.HCl, is near or at the chromophore, i.e. the retinal Schiff base of bR. The anesthetic action on bR purple membrane is probably via a specific site binding, but not a conformational mechanism. 相似文献
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Dennis Paul Valenzeno Edgar Arriaga John Trank Merrill Tarr 《Photochemistry and photobiology》1993,57(S1):996-999
Abstract— Though cellular photomodification has been shown to change cellular resting membrane potential, an effect of membrane potential on the rate of photomodification has never been reported. Here we demonstrate that the rate of photomodification of potassium channels in frog atrial cells is voltage dependent. The rate of potassium channel photomodification using negatively charged Rose Bengal as the photosensitizer is about 2.5 times greater at the resting membrane potential of -70 m V compared to +40 mV. Similar results are obtained using the positively charged photosensitizer methylene blue. On the other hand, the rate of photomodified increase of leak current in the same cells does not significantly change in this voltage range with Rose Bengal as photosensitizer, but demonstrates a voltage dependence like that of potassium current when methylene blue is the photosensitizer. These observations cannot be explained based on voltage-dependent partitioning of the sensitizer, as similar effects on potassium current were obtained using either a positively charged or negatively charged sensitizer. 相似文献
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等色染料离子对萃取光度法测定铜的研究——四溴荧光素·丁基罗丹明B体系 总被引:4,自引:0,他引:4
提出了等色染料离子对萃取光度法。利用四溴荧光素·丁基罗丹明B(TBF·BRB_2)染料离子对和铜氰络离子与丁基罗丹明B离子缔合物体系的两种离子对的等色生色效应提高了测定铜的灵敏度。方法由于用铜的特效试剂分离铜,选择性好。其摩尔吸光系数为2.45×10~5,铜含量在0~2.54μg/10ml之间遵守比耳定律。对含铜10~(-8)g·ml~(-1)的水样进行测定,相对标准偏差为3.6%。 相似文献
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Abstract— The effect of light-induced and salt-jump induced membrane potential on microsecond and millisecond delayed light emission from chloroplasts, following a single 10 ns flash, have been studied. Microsecond delayed light emission is shown to be independent of the membrane potential contrary to proposals that the activation energy for delayed light emission can be modulated by transmembrane electric fields. This result is discussed in terms of the possible origin of this short-lived emission. Millisecond delayed light after a single excitation flash is enhanced by membrane potential only if a proton gradient is present. By measuring changes in ms delayed light caused by simultaneous injection of KC1 and Na-benzoate (which creates a proton gradient) in the presence of valinomycin, the light-induced potential generated across the thylakoid membrane by a single excitation flash was calibrated and found to be 128 ± 10 mV in agreement with the recent measurements of Zickler and Witt (1976) based on voltage-dependent ionophores. It is concluded that the secondary charges that give rise to ms delayed light, after a single flash, do not fully span the membrane. 相似文献
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苯磺酸甲酯醇解反应的动力学研究 总被引:2,自引:0,他引:2
苯磺酸甲酯醇解反应的动力学研究赖国华,胡科诚,金松寿(杭州大学化学系杭州310028)关键词动力学,苯磺酸甲酯醇解,补偿效应本文研究了苯磺酸甲酯在CH_3OH,C_2H_5OH,n-C_3H_7OH和n-C-4H_9OH中的醇解反应速率随温度的变化情... 相似文献
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在CD-R光盘中,要求记录介质薄膜有良好的光学性能,这样才能降低噪音,提高数据存储与读取的可靠性.菁染料是应用最广泛的记录介质,本文采用旋涂法制备菁染料薄膜时,发现溶剂对薄膜的光学性能有很大的影响.通过AFM对薄膜表面的微观精细结构的研究表明,染料薄膜反射率的高低与薄膜表面粗糙度有关.其中使用氯仿、四氟丙醇和二丙酮醇作溶剂时,制备的染料薄膜表面平整,反射率较高;使用甲醇作溶剂时,染料薄膜布满直径0.3μm左右的晶粒,对光线有强烈散射作用,从而降低了染料薄膜的光学性能. 相似文献
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Abstract– Infrared difference spectra with 4 cm?1 spectral resolution and 10-u.s temporal resolution, obtained previously with a stroboscopic Fourier-transform difference technique (Braiman et al., 1991, Proc. Natl. Acad. Sci. USA 88, 2388), were analyzed by means of a global exponential fitting procedure based on singular value decomposition. Using a simple linear kinetic model K → L → M for the bacteriorhodopsin (bR) photocycle in the time range10–1000 μ.s at 16.5°C, it was possible to generate bR → L and bR → M difference spectra with signal/noise ratios comparable to those obtainable with low temperature difference spectroscopy. The resulting time-resolved bR → L and bR-→ M difference spectra are both very similar to the corresponding static FTIR difference spectra obtained at 175 K and 250 K, respectively. In the bR → L spectrum, however, there are interesting differences that may indicate a greater degree of deprotonation of Asp-96 when L is formed at physiological temperatures than when it is observed in a low-temperature steady state. 相似文献
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杯芳烃膜电极研究 总被引:4,自引:0,他引:4
用吸附法将 C-十一烷基间苯二酚杯 [4]芳烃固定在玻碳电极上制成杯芳烃膜电极 ,对DL-去甲肾上腺素、尿酸、DL-酪氨酸、邻苯二酚进行了测定 ,该电极对 DL-去甲肾上腺素和邻苯二酚具有良好的响应 ,其线性范围分别为 4.0× 1 0 -5~ 8.0× 1 0 -4 和 2 .0× 1 0 -4 ~ 2 .0× 1 0 -3mol·L-1,检测下限分别为 1 .2 5× 1 0 -5和 1 .0× 1 0 -5mol· L-1,对尿酸、DL -酪氨酸没有响应 ,试验发现杯芳烃膜电极不但具有选择性 ,而且有较快的响应速度、良好的重现性和稳定性。 相似文献
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Abstract— Resonance Raman spectra of photostationary state mixtures at — 80°C of bR568, L, L', and M for light-adapted bacteriorhodopsin were obtained. The approximate Raman spectrum of L + L' was obtained by computer, subtracting the known Raman spectra of bR568 and M from the photostationary state spectra. Several new species not previously observed with the bacteriorhodopsin photocycle have been proposed recently. We compare our results to these studies in order to investigate the photoreaction scheme of bacteriorhodopsin. 相似文献
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Abstract— The binding of neutral red to purple membrane has been studied. The intrinsic p K a and the apparent p K a , of bound neutral red were determined by titration and by measuring the binding ratio of neutral red to purple membrane as a function of pH. The surface potential of purple membrane was inferred from the difference between these two p K a s. The H+ /M412 ratio at different ionic strengths was also measured and compared with the surface potential. The results show that the H+ /M412 decreased as the surface potential increased due to decreased salt concentrations. However, this correlation holds only for KCl concentrations higher than 30 m M . At lower salt concentrations, the change in surface potential is always less than the variation in the H+ /M412 ratio. 相似文献
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本文用停流法和分光光度法研究了[Fe(por)Cl](por=原卟啉(pp)或对应的二甲酯(ppdme))与N-甲基咪唑(N-MeIm)的亲核取代反应动力学,讨论了反应机理,求得前置平衡的平衡常数(K)和基元步骤的速率常数(k1),研究了温度对反应动力学的影响,得到平衡步骤的和基元步骤的活化参数 相似文献
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甲烷常压O2部分氧化合成甲醛反应动力学 总被引:1,自引:0,他引:1
用Mo/SiO2催化剂在常压流动体系固定床反应器中进行了甲烷部分氧化合成甲醛反应的本征动力学研究,确定了反应途径和反应级数,通过Laplace变换计算了各步反应速度常数和活化能,给出了O2浓度和反应温度对产物分布和最佳空时的影响规律,并预测了不同反应温度下的最佳空时及空时收率(STY)。 相似文献
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Satoru Tokutomi Tatsuo Iwasa Tru Yoshizawa Shun-ichi Ohnishi 《Photochemistry and photobiology》1981,33(4):467-474
Abstract— Flash-induced changes in surface potential and fluidity of purple membrane were studied by a spin label method. Changes in surface potential and fluidity were monitored by observing the distribution of charged and uncharged spin labels between the purple membrane and the aqueous phase.
On flash illumination, a transient hyperpolarization of the surface potential and a transient fluidization of the membrane hydrophobic region are induced. The former may probably reflect the proton movement near the purple membrane surface, while the latter may result from photo-induced conformational changes of bacteriorhodopsin.
The two events are different in time course. The relationships between the two events, and the formation and decay of the intermediates of bacteriorhodopsin in the photoreaction cycle are discussed. 相似文献
On flash illumination, a transient hyperpolarization of the surface potential and a transient fluidization of the membrane hydrophobic region are induced. The former may probably reflect the proton movement near the purple membrane surface, while the latter may result from photo-induced conformational changes of bacteriorhodopsin.
The two events are different in time course. The relationships between the two events, and the formation and decay of the intermediates of bacteriorhodopsin in the photoreaction cycle are discussed. 相似文献