可可碱与牛血清白蛋白作用光谱特性的研究

本文应用荧光光谱法研究了可可碱（TB）与牛血清白蛋白（BSA）相互作用的光谱特性。测定了18℃、30℃、40℃温度下的结合常数KA分别为1．68×10^4、1．58×10^4、1．45×10^4L／mol,结合位点数咒分别为1．04、1．03、1．03。实验结果表明：TB对BSA内源荧光的猝灭机理主要为静态猝灭;热力学参数探讨其相互作用机理,TB主要以静电力与BSA相互作用;研究了TB对BSA构象的影响,BSA的荧光主要源于色氨酸残基。同时研究了Cu^2＋存在下TB与BSA的相互作用。     

6-苄氨基嘌呤与牛血清白蛋白作用荧光特性的研究

应用荧光光谱法研究了6-苄氨基嘌呤（6-BA）与牛血清白蛋白（BSA）相互作用的荧光特性。测得了6-BA与BSA在10、27、40℃温度下的结合常数KA为：0.21×10^5、1.37×10^5、5.53×10^5L/mol,结合位点数n为：1.0、1.2、1.3。6-BA对BSA内源荧光的猝灭机理主要为静态猝灭,6-BA主要以疏水作用与BSA相互作用,BSA的荧光主要源于色氨酸残基,6-BA对BSA的构象有影响。     

荧光光谱法研究氰戊菊酯与牛血清白蛋白的结合反应

在生理酸度条件下,应用荧光光谱法和紫外一可见光谱法,研究了在不同温度下氰戊菊酯与牛血清白蛋白（BSA）的结合反应。实验发现,氰戊菊酯对BSA的内源荧光有较强的猝灭作用,且此荧光猝灭机理为动态猝灭。由热力学参数焓变△H=17.78kJ·mol^-1,熵变△S=143.65J·mol^-1·K^-1,推断出氰戊菊酯与BSA结合反应主要由疏水作用力驱动。根据Fǒrster非辐射能量转移理论,计算出供体（BSA）-受体（氰戊菊酯）间的结合距离为4.28nm,能量转移效率为0.0699。三维荧光光谱表明氰戊菊酯的存在使BSA的构象发生了变化。此外,还考察了某些金属离子对氰戊菊酯与BSA结合反应的影响。     

毛细管电泳对盐酸普罗帕酮与人血清白蛋白结合作用的研究

采用毛细管区带电泳（CZE）技术,研究了盐酸普罗帕酮（propafenone hydrochloride）与人血清白蛋白（HSA）的结合作用机制。在以硼砂-碳酸氢钠（pH10,50mmol／L）为运行缓冲溶液,运行电压17kV,进样时间12s,紫外检测器（214 nm）的条件下检测,结合常数和结合位点数在298K和310K分别为心。=2．24×10^7 L·mol^-1,n298k=1．2及K310k=3．12×10^7 L·mol^-1,n310K=1．3。同时运用荧光光谱研究了盐酸普罗帕酮与人血清白蛋白的结合作用机制;并从热力学参数推得了药物分子与人血清白蛋白分子间的作用力类型等分子间的相互作用信息。     

邻菲咯啉乳酸镍配合物的合成与表征及其与牛血清白蛋白相互作用的荧光分析

利用溶液法合成了配合物[Ni(Hlact)₂(phen)]·2H₂O(1),并对该配合物进行了元素分析、红外光谱和X-射线单晶衍射表征。通过荧光光谱法研究了不同温度下配合物1与牛血清白蛋白相互作用的荧光强度的变化,计算在不同温度下,配合物1与牛血清白蛋白(BSA)的结合常数、结合位点数以及热力学函数,进一步讨论了配合物1与BSA相互作用的作用力类型和两者之间的距离。结果表明,配合物1对牛血清白蛋白的荧光猝灭为静态猝灭过程,它与牛血清白蛋白的相互作用有一个位点,结合常数的平均值5.06×10⁵ L·mol^-1,作用距离为2.35 nm,相互作用力表现为氢键和范德华相互作用。     

胡椒酸与牛血清白蛋白相互作用的研究

用荧光光谱及紫外光谱法模拟研究生理条件下胡椒酸与牛血清白蛋白(BSA)的相互作用。结果表明,胡椒酸与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。胡椒酸对BSA的猝灭速率常数Kq为2.969×1013(18℃)、2.491×1013(25℃)和2.328×1013L·mol-1·s-1(37℃)。胡椒酸与BSA的结合常数KA为1.01×105(18℃)、2.06×104(25℃)和1.02×104L·mol-1(37℃),结合位点数n为0.90(18℃)、0.77(25℃)和0.72(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2.47(18℃)、2.52(25℃)和2.54(37℃)nm。确定胡椒酸与BSA有较强的相互作用,可以被蛋白质所储存和运输。     

左旋紫草素与溶茵酶相互作用的研究

利用荧光猝灭方法结合紫外光谱（UV）、傅立叶红外光谱（FT—IR）和圆二色性光谱（CD）,在模拟生理条件下研究了左旋紫草素和溶菌酶的结合常数、主要作用力以及左旋紫草素对溶菌酶二级结构的影响。在温度为296、303和310K时,根据Scatchard方程测得左旋紫草素和溶菌酶的结合常数分别为3．022×10^4、1．894×10^4、0．9581×10^4L·mol-1,结合位点数分别为0．98、0．76、0．68;焓变（△H）和熵变（AS）分别为-14．78kJ／mol、24．26J／（mol·K）,结果表明其主要作用力为疏水性和静电作用力。同步荧光和紫外光谱研究进一步证明左旋紫草素与溶菌酶有着较强的结合,左旋紫草素对溶菌酶的荧光猝灭为多种机理同时存在,并根据Fbrster能量非辐射转移理论测得结合位置与色氨酸残基问的距离r为4．62nm。CD和frr—IR研究显示,左旋紫草素使溶菌酶的二级结构发生了变化。该文为左旋紫草素在人体内的储存、运输、作用机理及临床试验提供了具有指导作用的信息。     

孔雀石绿与牛血清白蛋白的相互作用

运用荧光光谱和紫外-可见吸收光谱研究了在缓冲溶液中不同温度下孔雀石绿(MG)与牛血清白蛋白(BSA)之间的相互作用. 实验结果表明, MG对BSA的内源荧光猝灭为静态猝灭过程. 测定了该反应在不同温度下的结合常数KA, KA分别为7.69×10⁴ L·mol-1(10 ℃)、5.31×10⁴ L·mol-1(20 ℃)和4.85×10⁴ L·mol-1(37 ℃), MG与BSA以摩尔比1:1结合. 根据Forster非辐射能量转移理论, 求出了37 ℃时给体(MG)和受体(BSA)之间能量转移效率和结合距离分别为E=0.1635 和r=2.30 nm. 计算出的热力学参数表明, MG 和BSA之间的作用力主要是通过氢键和范德华力相互作用.     

分光光度法测定水样中阴离子表面活性剂——基于溴甲酚紫和溴化十六烷基吡啶混合溶液间增色反应

试验发现：在pH6．4的磷酸盐缓冲介质中,含有溴甲酚紫及溴化十六烷基吡啶的混合溶液在586nm波长处的吸收强度因加入某种阴离子表面活性剂（如十二烷基磺酸钠SLS或十二烷基硫酸钠SDS）而增加,并其增强程度与所加入的阴离子表面活性剂的浓度在一定范围内呈线性关系。经测定,SLS的线性范围在2．13×10^-5mol·L^-1以内,SDS的线性范围在2．15×10^-5mol·L^-1以内。两者的检出限（3S）依次为4．92×10^-7,8．54×10^-7mol·L^-1,两反应的摩尔吸光率依次为2．94×10^4,1．58×10^4L·mol^-1·cm^-1。将此方法应用于一些水样中阴离子表面活性剂（以SLS表示）的测定,测得其回收率在98．8％～101．9%之间,测定结果的相对标准偏差（n=6）均小于2％。     

胡椒酸丁二醇单脂与牛血清白蛋白相互作用的研究

运用荧光及紫外-可见吸收光谱法研究了胡椒酸丁二醇单酯(简称BPM)与牛血清白蛋白(BSA)的相互作用。实验结果表明,胡椒酸丁二醇单酯与BSA形成基态复合物导致BSA内源性荧光猝灭,猝灭机理主要为静态猝灭和非辐射能量转移,其猝灭速率常数为Kq为1.077×1013L/(mol.s)(25℃)、0.946×1013L/(mol.s)(37℃)。利用荧光猝灭反应测得结合常数KA为2.6×106(25℃)、3.4×106(37℃),结合位点数n为1.30(25℃)、1.33(37℃)。根据Frster能量转移理论得到结合距离r=2.92nm(25℃)、2.66nm(37℃)和能量转移效率E=0.45(25℃)、0.43(37℃)。通过热力学参数计算,确定胡椒酸丁二醇单酯与BSA的相互作用是熵增加和吉布斯自由能降低的自发过程,主要作用力是疏水作用力。     

Cu+和Ag+叠氮盐晶体的周期性ab initio计算

过渡金属叠氮盐为化学结构简单的爆燃爆炸性物质．可作为起爆剂或快速反应研究的模型体系。在炸药化学、固体化学和固体物理等领域受到广泛关注．其晶体结构、物理、化学和爆炸性质已有许多报道．但迄今对该类化合物的理论研究方法仅局限于半经验的DV-Xa方法和EH-CO法．     

Study on Gd3+ and Sm3+ co-doped ceria-based electrolytes

Doped ceria electrolytes of Ce_1-aGd_a-ySm_yO_2–0.5a, wherein a=0.15 or 0.2, and 0ya, were prepared with the citrate method, and characterized by inductively coupled plasma–atomic emission spectrometry, energy dispersive spectrometry, scanning electron microscopy, powder X-ray diffraction, and AC impedance spectroscopy. The effect of composition on the structure and conductivity was studied. All the samples were fluorite-type ceria-based solid solutions. For the singly doped samples, the optimal composition was Ce_0.85Gd_0.15O_1.925 for Gd³⁺-doped ceria (CGO), which showed higher ionic conductivity than the best Sm³⁺-doped ceria (CSO) at 773–973 K. For the co-doped samples, the ionic conductivities were higher than those of the singly doped ones in the temperature range 673–973 K when a=0.15, but only better in 673–773 K when a=0.2. For the samples of Ce_0.85Gd_0.15-ySm_yO_1.925, wherein 0.05y0.1, much higher ionic conductivity was observed than those of the singly doped ceria at 773K~973 K. Therefore, these co-doped samples would be better than CGO and CSO to be the electrolytes of intermediate-temperature solid oxide fuel cells.     

Energy transfer between Gd3+ and Sm3+ the effect of Gd3+ on quenching of Sm3+ and intensity parameters of Sm3+ in borate glasses

Intensity parameters of Sm³⁺ in borate glasses were obtained by fitting the oscillator strengths to the Judd-Ofelt formula and a study of energy transfer from gadolinium to samarium was performed. An increase of samarium fluorescence originating from the ${}^4\text{G}{}_{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}$ level was observed in the presence of gadolinium, in the concentration range of 0.1–3 wt% samarium with gadolinium constant at 3 wt%. The intensity of samarium fluorescence on excitation at 273 nm increased by one order of magnitude in the presence of gadolinium. From the excitation spectrum of the double-doped glasses (Gd + Sm), it was deduced that energy absorbed by gadolinium is transferred from ${}^6\text{P}{}_{\mathrm{<mtext>7</mtext><mtext>2</mtext>}}$ gadolinium levels to the ${}^4\text{P}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}$ and ${}^4\text{P}{}_{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}$ samarium levels.The mechanism of this energy transfer was obtained by plotting the energy transfer probabilities as a function of samarium concentration. A linear dependence of $\text{η}{}_0\text{η}$ (η intensity of gadolinium in the presence of samarium) versus square of concentration of Sm + Gd is obtained. From this it is concluded that the transfer is of electric-multipolar type, mainly dipole-dipole. A small increase (about 10%) of fluorescence of samarium in the presence of gadolinium excited at levels where no energy transfer can take place is attributed to the fact that the quenching of samarium occurring by the cross relaxation $\text{(}{}^4\text{G}{}_{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}\text{→}{}^6\text{F}{}_{\mathrm{<mtext>9</mtext><mtext>2</mtext>}}\text{) (}{}^6\text{H}{}_{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}\text{→}{}^6\text{F}{}_{\mathrm{<mtext>9</mtext><mtext>2</mtext>}}\text{)}$ is suppressed by the presence of gadolinium as seen from concentration dependence of samarium doped glasses compared to double-doped glasses.     

TiP+6, Ti2P+6二元团簇的密度泛函理论研究

利用含有电子相关效应校正的密度泛函理论DFT中的B3LYP方法，选择LANL2DZ双ξ基组，并考虑极化函数，对TiP6^ ,Ti2P6^ 二元团簇各种可能存在的几何构型及电子结构进行了密度泛函理论研究，得到了TimPn^ 二元团簇的最稳定构型，其中TiP6^ 的最稳定构型为具有C3v对称性的半笼状结构，Ti2P6^ 的最稳定构型为具有D6h对称性的六角双锥，所得构型很好地说明了激光光解的实验结果。     

Adsorption of Co2+ and Zn2+ on cryptomelane-type hydrous managese dioxide

Co²⁺ and Zn²⁺ ions are adsorbed on cryptomelane-type MnO₂ by exchange with surface protons and with structural ions (probably K⁺ and/or Mn²⁺) in the oxide. The latter sites are responsible for the much higher capacity to these cations, compared to Na⁺. At all pH values, two straight lines expressing the presence of mainly two groups of sites with distinctly different adsorption energies are located in the Langmuir plots for both Co²⁺ and Zn²⁺. The apparent capacities of the two groups increase with the increase of pH, indicating the involvement of protons in the adsorption process over the whole concentration range. The higher Co²⁺ capacity at relatively low pH, compared to the Zn²⁺ capacity, is probably due to a more exchange with the structural ions. Crytomelane type MnO₂ seems to be a quite heterogenous ion adsorbent whose adsorption sites could be approximated to two groups only.     

Multi-reference configuration interaction calculations on the systems Xe 2 + and Xe 3 +

Potential curves for the ground (²Σ _u ⁺ ) and the three lowest excited states of the Xe ₂ ⁺ dimer ion (²Π _g ,²Π _u ,²Σ _g ⁺ ) have been calculated using pseudopotentials in MRD-CI (multi-reference single anddouble excitationconfigurationinteraction) calculations. Spin-orbit interaction — leading to the six states 1.(1/2) _u , 1.(3/2) _g , 1.(3/2) _u , 1.(1/2) _g , 2.(1/2) _u , 2.(1/2) _g — has been taken into account using a semiempirical technique [1]. Subsequently, starting with a relaxed Xe ₂ ⁺ ion in its ground state, the potential energy surface for the system Xe-Xe ₂ ⁺ was studied. We found that the collinear approach of the Xe atom leads to the most stable geometry. This is a linear symmetric molecule with bond lengths of 6.38 bohr. In the bestT-shaped structure, the Xe atom is 7.83 bohr away from the midpoint of the Xe ₂ ⁺ (r=6.1 bohr) dimer. The calculated binding energy of 0.25 eV for the equilibrium structure of the Xe ₃ ⁺ molecule (i.e. the linear symmetric geometry), is in very good agreement with experimental results of 0.27 ± 0.02 eV [2].     

Theoretical Investigation on the Electronic and Geometric Structure of GaN2+ and GaN4+

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.     

H+-Ca2+ Equilibrium Exchange on Polyacrylic Cationites

Potentiometric titration curves of carboxyl-containing polyacrylic cation exchangers (Amberlite IRC 86, Dowex MAC 3, Lewatit CNP 80, Purolite C 104, and Relite CNS) in the H form with calcium ions were measured. It was found that the apparent equilibrium constant strongly depended on the composition of resinate solutions, which was indicative of significant deviations of solutions in the cation exchanger gel phase from the ideal behavior. The largest deviations were observed for Dowex MAC 3 ion exchanger, and the smallest, for Amberlite IRC 86. For the other sorbents, the dependences coincided to within measurement errors. The experimental data were treated in terms of six models of the theory of exchange equilibria. The best approximation to titration curves was obtained in terms of the model that suggested the presence of two types of exchange centers in ion exchangers and took into account the influence of the state of three neighboring fixed groups on each spatially separated center. The amounts of centers of all types in the ion exchangers were determined. Differences in the selectivity of the cation exchangers with respect to calcium ions were explained.     

Theoretical investigation on the electronic and geometric structure of GaN2+ and GaN4+

The electronic and geometric structures of gallium dinitride cation, GaN2+ and gallium tetranitride cation, GaN4+ were systematically studied by employing density functional theory (DFT-B3LYP) and perturbation theory (MP2, MP4) in conjunction with large basis sets, (aug-)cc-pVxZ, x = T, Q. A total of 7 structures for GaN2+ and 24 for GaN4+ were identified, corresponding to minima, transition states, and saddle points. We report geometries and dissociation energies for all the above structures as well as potential energy profiles, potential energy surfaces, and bonding mechanisms for some low-lying electronic states. The calculated dissociation energy (De) of the ground state of GaN2+, X1Sigma+, is 5.6 kcal/mol with respect to Ga+(1S) + N2(X1Sigmag+) and that of the excited state, ?3Pi, is 24.8 kcal/mol with respect to Ga+(3P) + N2(X1Sigmag+). The ground state and the first excited minimum of GaN4+ are of 1A1(C2v) and 3B1(C2v) symmetry with corresponding De of 11.0 and 43.7 kcal/mol with respect to Ga+(1S) + 2N2(X1Sigmag+) for X1A1 and Ga+(3P) + 2N2(X1Sigmag+) for 3B1.