粉防己碱与牛血清白蛋白相互作用的研究

利用荧光光培和紫外-可见吸收光谱,研究了粉防己碱与BSA相瓦作用的光谱学行为.研究结果表明,粉防己碱埘BSA有较强的荧光猝灭作用,静态猝灭和非辐射能量转移是导致粉防己碱猝火BSA内源荧光的主要原因.利用Stern-Volmer方程处理实验数据,获得了猝火常数Ksv,不同温度下的Ksv分别为1.26×104 L·mol-1(300 K),1.17×104 L·mol-1(310 K),1.12×104 L·mol-1(320 K).根据Forster非辐射能量转移理论计算出了粉防己碱与BSA间的结合距离r(300 K:3.24 nm;310 K:3.31 nm;320 K:3.50nm).此外,还求得了粉防己碱与BSA的结合常数KA(300 K:1.52×105 L·mol-1;310 K:2.03×105 L·mol-1;320 K:2.89×105 L·mol-1)及相应温度下的热力学参数,热力学数据表明二者主要靠疏水作用力结合.粉防己碱与BSA相互作用的同步荧光光谱表明,二者的结合对BSA构象产生了影响.     

胡椒酸乙酯与牛血清白蛋白的相互作用及金属离子的影响

采用荧光光谱研究了胡椒酸乙酯与牛血清白蛋白(BSA)的相互作用。实验结果表明:胡椒酸乙酯与BSA形成基态复合物从而猝灭BSA的内源性荧光,猝灭原因主要为静态猝灭和非辐射能量转移作用。胡椒酸乙酯对BSA的猝灭速率常数Kq为1.451×1013L.mol-1.s-1(25℃)和1.136×1013L.mol-1.s-1(37℃),胡椒酸乙酯与BSA的结合常数KA为9.484×105L.mol-1(25℃)和1.355×106L.mol-1(37℃),结合位点数n为1.18(25℃)和1.24(37℃)。根据Frster偶极-偶极非辐射能量转移理论得到结合距离r为2.68 nm(25℃)和2.81 nm(37℃)。通过热力学参数的计算,确定胡椒酸乙酯与牛血清白蛋白的相互作用是熵增加和吉布斯自由能降低的自发过程,主要作用力为疏水作用力。讨论了共存金属离子对胡椒酸乙酯与BSA的相互作用的影响。     

7-羟基香豆素与三种芳香族氨基酸作用的荧光光谱研究

运用荧光光谱和紫外光谱研究7-羟基香豆素UBM分别与色氨酸Trp,酪氨酸Tyr和苯丙氨酸Phe三种芳香族氨基酸的相互作用。结果表明在模拟人体生理条件下,UMB能引起上述氨基酸发生荧光猝灭,最大猝灭波长依次为347,303和282 nm,猝灭机制均为静态猝灭,相互之间均以摩尔比1：1形成了复合物,且得到两种温度下UMB与Trp,Tyr和Phe反应的表观平衡常数K_c分别为298.15 K时2.993×106,7.858×104和1.186×103 L·mol-1,310.15 K时2.702×104,1.063×105和8.352×103 L·mol-1。热力学函数变化表明UMB与以上三种氨基酸结合作用较强,其中UMB-Trp相互作用力是氢键或范德华力,UMB-Tyr和UMB-Phe相互作用主要以疏水作用为主,同时都可能存在偶极-偶极之间的相互作用。     

荧光光谱法研究虎杖苷与牛血清白蛋白的相互作用

在不同温度下,采用荧光光谱,紫外-可见吸收光谱研究了虎杖苷与牛血清白蛋白(BSA)的相互作用。虎杖苷对BSA的荧光有较强的猝灭作用。根据292K和311K时虎杖苷对BSA的荧光猝灭作用,利用Stern-Volmer方程及双倒数方程处理实验数据,表明虎杖苷对BSA的荧光猝灭作用属于动态猝灭过程,根据Foerster非辐射能量转移理论计算出了虎杖苷与BSA间的结合距离r=3.61nm,结合常数(Kb)分别为5.189×105L·mol-1(292K),1.382×105L·mol-1(311K)及对应温度下的热力学参数。实验结果表明二者主要靠疏水作用力结合,采用同步荧光光谱探讨了虎杖苷对BSA构象的影响。     

头孢噻肟钠与牛血清白蛋白的相互作用

采用荧光光谱、同步荧光光谱、紫外光谱研究了水溶液中头孢噻肟钠(CTX)与牛血清白蛋白(BSA)之间的相互作用.结果表明:CTX能显著猝灭BSA的内源荧光并以静态猝灭为主;两者以摩尔比1∶1结合,结合常数分别为1.20×104(298K)、7.63×103(308K)和6.69×103(313K)L·mol-1;根据热力学参数判断CTX与BSA之间的作用力主要为氢键和范德华力;依据Foester非辐射能量转移理论计算出CTX与BSA之间的结合距离r为3.26nm,同步荧光光谱研究表明CTX能够使BSA构象发生变化.     

阿维菌素与牛血清白蛋白作用的光谱研究

依据阿维菌素与牛血清白蛋白的结合作用使牛血清白蛋白内源荧光发生改变的现象,用荧光光度法研究了在一定条件下阿维菌素和牛血清白蛋白相互作用的机理。结果表明,阿维菌素对牛血清白蛋白的荧光猝灭是形成了超分子化合物的静态猝灭过程。测定了在不同温度下阿维菌素与牛血清白蛋白的结合常数KA和结合位点数n分别为KA=2.26×103L·mol-1,n=1.08(25℃);KA=1.35×103L·mol-1,n=1.05(35℃)。根据阿维菌素与牛血清白蛋白相互作用的热力学参数,确定了阿维菌素与牛血清白蛋白之间的作用力类型为氢键和范德华力;根据Foerster非辐射能量转移理论求得阿维菌素与牛血清白蛋白的结合距离为2.55nm。用同步荧光光谱确定阿维菌素影响了BSA微区的构象。     

葛根素与牛血清白蛋白相互作用的研究

应用荧光光谱法研究了生理条件下(pH7.4)葛根素(PUE)与牛血清白蛋白(BSA)的相互作用。结果表明,葛根素对BSA荧光的猝灭机制属于形成复合物的静态猝灭过程,求得其猝灭常数为7.29×1012 L·mol-1·s-1,结合常数为5.04×104 L·mol-1;根据Frster非辐射能量转移理论,测得葛根素在BSA中的结合位置与色氨酸残基间的距离为3.35 nm;探讨了葛根素对蛋白质空间结构的影响及其相互作用机理;考察了体内某些共存金属离子对葛根素与BSA结合作用的影响。     

防己诺林碱与牛血清白蛋白相互作用的研究

在不同温度下,用荧光猝灭光谱、同步荧光光谱和紫外-可见吸收光谱,研究了防己诺林碱与BSA相互作用的光谱学行为。防己诺林碱对BSA有较强的荧光猝灭作用。根据不同温度下防己诺林碱对BSA的荧光猝灭作用,利用Stern-Volmer方程处理实验数据,表明防己诺林碱对BSA的荧光猝灭作用属于静态猝灭。根据Frster非辐射能量转移理论计算出了防己诺林碱与BSA间的结合距离R(27 ℃ 2.51 nm; 37 ℃ 2.72 nm; 47℃ 2.89 nm)、结合常数K_A(27 ℃ 1.05×105 L·mol-1; 37 ℃ 3.31×105 L·mol-1; 47 ℃ 7.24×105 L·mol-1)及对应温度下的热力学参数。热力学数据表明二者主要靠疏水作用力结合,同时用同步荧光光谱探讨了防己诺林碱对BSA构象的影响。     

荧光光谱法研究四苯基-锌金属卟啉与蛋白质的相互作用机理

利用荧光光度法研究了meso-四(4-羟基苯基)卟啉-锌金属卟啉(TPP-Zn)与牛血清白蛋白(BSA)之间的结合反应。TPP-Zn对于BSA有荧光猝灭作用,基于TPP-Zn对BSA内源荧光的猝灭机理,测定了两者之间在不同温度下的结合常数,温度在27,35和42 ℃时,利用荧光猝灭法测得的结合常数K分别为1.521×106 L·mol-1,7.048×105 L·mol-1,1.473×105 L·mol-1,各温度下的最大扩散碰撞猝灭速率常数K_q均大于2.0×1010 L·mol-1·s-1,由此判定猝灭类型为静态猝灭。根据Frster非辐射能量转移理论,确定了TPP-Zn与BSA之间的能量转移效率E,能量给体(BSA)与受体(TPP-Zn)之间的结合距离r=3.72<7 nm,符合非辐射能量转移条件。依据热力学参数ΔG<0,ΔH<0和ΔS>0确定了TPP-Zn与BSA之间的作用力主要是静电引力。     

荧光法对姜黄素与牛血清白蛋白相互作用的研究

应用荧光光谱法研究了生理条件下(pH7.4)姜黄素(Curcumin)与牛血清白蛋白(BSA)的相互作用。实验结果表明,姜黄素对BSA产生荧光猝灭作用,其机理属于静态猝灭过程。T=310K时,其猝灭常数为1.388×1012L.mol-1.s-1,表观结合常数为2.387×104L.mol-1。根据Foerster非辐射能量转移理论,测得姜黄素在BSA中的结合位置与色氨酸残基间的距离为4.43nm。探讨了姜黄素对BSA构象的影响及结合机理,考察了体内某些共存金属离子对姜黄素与BSA结合作用的影响。     

Guided-Wave Two-Dimensional Acousto-Optic Scanner Using Proton-Exchanged Lithium Niobate Waveguide

Two-dimensional scanning of a 0.6328 mum guided-light beam has been realized using noncolinear acousto-optic (AO) coplanar Bragg diffraction together with colinear AO guided-mode to substrate radiation-mode conversion in a Z-cut Xpropagation LiNbO3 proton-exchanged (PE) waveguide. The two surface acoustic (SAW) waves utilized are at the center frequencies of 500 and 200 MHz, propagating in the Y and X axes, respectively. Two-dimensional scanning of approximately 720 resolvable light beam spots, namely, 18 40 (horizontal vertical) scanning, has been demonstrated using a light beam of 1.0 mm aperture. The total number of resolvable beam spots can be greatly increased from 720 by simply utilizing SAW transducers of larger bandwidth and a light beam of greater aperture. It should also be possible to significantly increase the diffraction efficiency from 3 % by optimizing the parameters of the PE waveguide and the SAWs.     

Effect ofγ-radiation on the spectral luminescence characteristics of impure cadmium tungstate crystals

Results of a study of the effect of γ-radiation on the spectral luminescence properties of cadmium tungstate crystals doped with silver, bismuth, and molybdenum cations are presented. Spectral characteristics of the nondnnnoped crystals are briefly described. Absorption and photo and X-ray luminescence spectra of the crystals taken before and after exposure to γ-radiation (5.5·10⁴ Gy) are compared. It is found that the spectral characteristics of the crystals doped with silver, bismuth, and molybdenum cations do not change markedly after the exposure. The relation between the type of impurity-induced defects, individual characteristics of the impurity cations, and the character of the effect of γ-radiation on the spectral luminescence properties of impure crystals is analyzed (preliminarily). Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 1, pp. 55–60, January–February, 1997.     

Measurement of nonlinear coefficient of optical fiber based on small chirped soliton transmission

We measure the waveform and phase curves of short optical pulses before and after transmission over different lengths of fibers by use of the pulse analyzer with the frequency-resolved optical gating (FROG),and numerically simulate pulse evolution under the experimental conditions.The nonlinear coefficient of the fiber is given by comparing the experimental results with the numerical ones.Difference between the experiment and numerical simulation is analyzed.     

Resonance scattering of canonical elastic shells in absorbing fluid medium

Resonance scattering of elastic spherical shell and cylindrical shell while the surrounding fluid medium has absorption is studied. The normal mode solution derived using exact elastic theory and the separation of variables is still applicable. However, the scattering form function has to be modified for the absorbing medium, otherwise the unreasonable result would be obtained. The backscattering form function in the absorbing medium is redefined, and the form function of elastic spherical and cylindrical shell with vacuum or solid matter filled is calculated in various absorption conditions. The results show that the absorption of surrounding fluid leads to notable attenuation of the coincidence resonances in the mid-frequency, but it has a little influence on the low-frequency resonance scattering induced by the filler inside the shell.     

Single-beam self-referenced phase-sensitive surface plasmon resonance sensor with high detection resolution

A versatile and low-cost single-beam self-referenced phase-sensitive surface plasmon resonance(SPR)sensing system with ultra-high resolution performance is presented.The system exhibits a root-mean-square phase fluctuation of ±0.0028.over a period of 45 min.i.e.a resolution of±5.2×10-9 refractive index units.The enhanced performance has been achieved through the incorporation of three design elements:a true single-beam configuration enabling complete self-referencing so that only the phase change associated with SPR gets detected,a differential measurement scheme to eliminate spurious signals not related to the sensor response,and the elimination of retardation drifts by incorporating temperature stabilization in the liquid crystal phase modulato .Our design should bring the detection sensitivity of non-labeling SPR biosensing closer to that achievable by conventional fluorescence-based techniques.     

Influences of SiO2 protective layers and annealing on the laser-induced damage threshold of Ta2O5 films

Ta2O5 films are prepared on BK7 substrates with conventional electron beam evaporation deposition.The effects of SiO2 protective layers and annealing on the laser-induced damage threshold (LIDT) of the films are investigated.The results show that SiO2 protective layers exert little influence on the electric field intensity(EFI)distribution,microstructure and microdefect density but increase the absorption slightly.Annealing iS effective on decreasing the microdefect density and the absorption of the films.Both SiO2 protective layers and annealing are beneficial to the damage resistance of the films and the latter is more effective to improve the LIDT.Moreover,the maximal LIDT of Ta2O5 films is achieved by the combination of SiO2 protective layers and annealing.     

A stereo matching algorithm using multi-peak candidate matches and geometric constraints

Gray cross correlation matching technique is adopted to extract candidate matches with gray cross correla- tion coefficients less than some certain range of maximal correlation coefficient called multi-peak candidate matches. Multi-peak candidates are extracted corresponding to three closest feature points at first. The corresponding multi-peak candidate matches are used to construct the model polygon. Correspondence is determined based on the local geometric relations between the three feature points and the multi-peak candidates. The disparity test and the global consistency checkout are applied to eliminate the remaining ambiguous matches that are not removed by the local geometric relational test. Experimental results show that the proposed algorithm is feasible and accurate.     

Fiber Modal Index Measurements Based on Fiber Gratings

A novel method based on fiber gratings for measuring the effective indices of fiber modes is proposed. The effective index difference between the core mode and a cladding mode was obtained by analyzing the interference fringe of a pair of cascaded long-period fiber gratings. In order to extract the core mode index from the measured index difference, an index matching oil immersion method is proposed. By analyzing the interaction between the cladding mode and the oil applied on the cladding surface, the mode order and the effective index of the involved cladding mode might be calculated. Experimental results about the interference fringe shifts induced by the oil index and the oil-applied length are also presented.     

Optical Pulse Compression Schemes That Use Nonlinear Bragg Gratings

Nonlinear optical pulse compression of picosecond pulses typically requires long lengths of optical fiber and multiple components. Periodic structures, such as fiber Bragg gratings, are highly dispersive at wavelengths outside of the photonic bandgap. This implies that such gratings can be used as very short all-fiber compressors. In this paper a number of such compression schemes are reviewed involving uniform and nonuniform fiber Bragg gratings, relying on both soliton and nonsoliton compression principles. Experimental results supporting the corresponding underlying theory are also presented. Finally, an extension of one of the compression schemes is shown, which allows the generation of adjustable high-repetition rate soliton trains.