基于羟苯基苯并咪唑的Zn2+比率荧光探针

通过羰基将两分子2-(4-氨基-2-羟苯基)苯并咪唑(4-AHBI)连接,合成了结构高度对称的新化合物N,N′-二-[3-羟基-4-(2-苯并咪唑)苯基]脲(C27H20N6O3,1),测试了不同溶剂条件下1的紫外吸收和荧光发射光谱,研究了1对Zn2+的选择性识别作用。结果表明,随着溶剂极性的增大,1的紫外吸收峰发生蓝移,激发态分子内质子转移(ESIPT)荧光发射峰明显增强。与4-AHBI相比,1在乙腈溶液中的紫外吸收强度增强约3.5倍,最大吸收峰红移8 nm,荧光发射增强8倍多。1在乙腈溶液中的Zn2+荧光响应行为表明1与Zn2+的结合将导致1在445 nm处的荧光强度不断降低,而在395 nm处出现的新峰的荧光强度不断增强,具有比率荧光探针的特点,而且检测范围较宽,可达1×10-6-1×10-2 mol.L-1。     

Systematic assignment of NMR spectra of 5‐substituted‐4‐thiopyrimidine nucleosides

Unambiguous characterization of 5‐substituted‐4‐thiopyrimidine nucleosides (ribonucleosides and 2'‐deoxynucleosides) was performed using NMR spectroscopy. Assignments of all proton and carbon signals of 5‐bromo‐4‐thiouridine and related nucleosides were systematically carried out and firmly established by COSY and HMQC techniques. The NMR data of various 4‐thiopyrimidine nucleosides are compared, and the key contributing factors discussed. The approach presented here is applicable to other modified nucleosides and nucleotides, as well as nucleobases. Copyright © 2013 John Wiley & Sons, Ltd.     

光谱法研究Fe(Ⅲ)与细胞色素b5的相互作用

用荧光光谱、时间分辨荧光光谱、圆二色谱(CD)和紫外吸收光谱研究了细胞色素b5(cyt b5)与Fe(Ⅲ)的相互作用。结果表明,Fe(Ⅲ)对cyt b5有较强的荧光猝灭作用。用Stern-Volmer方程处理实验结果,并结合时间分辨荧光光谱证明,Fe(Ⅲ)对cyt b5的猝灭机制主要为静态猝灭;Fe(Ⅲ)与cyt b5发生分子内的非辐射能量转移,根据Frster非辐射能量转移理论确定了给体-受体间的结合距离r为5.13nm。同时,用圆二色谱及同步荧光光谱探讨了Fe(Ⅲ)对cyt b5构象的影响。     

多光谱法与分子对接模型研究西维来司钠与弹性蛋白酶的相互作用

采用多种光谱法及分子对接技术对西维来司钠（ONO-5046）与弹性蛋白酶的相互作用进行研究,利用荧光光谱法判断出ONO-5046的加入对弹性蛋白酶产生荧光猝灭作用,与弹性蛋白酶相互作用的猝灭类型为静态猝灭,ONO-5046与弹性蛋白酶以结合比为1∶1的比例构成复合物。经计算,ONO-5046与弹性蛋白酶体系的ΔH<0和ΔS<0,判断出氢键与范德华力为其主要结合作用力,由ΔG<0可知该反应可以自发进行。同步荧光光谱法、紫外-可见分光光谱法和圆二色光谱法探讨了ONO-5046的加入使弹性蛋白酶中氨基酸残基周围环境的疏水性降低,二级结构发生改变,α-螺旋结构的比例减少,无规则卷曲的比例增多;分子对接模拟结果表明：在与弹性蛋白酶相互作用过程中,ONO-5046分子骨架上的多个酰基结构、2个苯环以及较长的共轭结构能提供氢键与范德华力的作用位点,同时,端碳上的3个甲基结构有利于疏水作用,ONO-5046上的氧负离子与弹性蛋白酶的精氨酸存在盐桥作用。以上结果表明,ONO-5046与弹性蛋白酶的结合存在多种作用力,能形成稳定的复合物,从而抑制了弹性蛋白酶的活性。     

Effect of specific rotation of chiral dopant and polymerization temperature on reflectance properties of polymer stabilized cholesteric liquid crystal cells

A series of polymer stabilized cholesteric liquid crystal (PSCLC) cells were prepared by photo‐polymerization of a cholesteric liquid crystal (Ch‐LC) mixture containing a nonreactive LC, a nematic diacrylate and a novel cholesteryl monomer. The influence of the specific rotation and concentration of the chiral dopants, and the polymerization temperature on reflection properties was investigated. The results demonstrate that the reflection band was broadened after polymerization for all the systems both left‐handed S811 and right‐handed R1011 as the chiral dopant, which is speculated to be a result of an inhomogeneous consumption of the chiral monomer within the system. Additionally, the polymer temperature plays an integral role in the observed reflection spectra, and at optimum polymerization temperature the broadband reflection effect becomes much more pronounced. Scanning electron microscopy (SEM) was used to examine the role of microscopic changes of the polymer network induced by polymerization temperature. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1562–1570, 2008     

分光光度法快速测定海虾中呋喃唑酮残留量

建立了快速检测水产品中呋喃唑酮残留量方法.采用分光光度法,以校准曲线法、标准加入法检测海虾、养殖虾中呋喃唑酮残留量.结果表明,本方法线性范围为0.25-20.0μg/mL,r=0.9988,检出限为2.5μg/kg,相对标准偏差＜4.3%,回收率为97%-102%.方法准确、灵敏、简便,适合实验室快速检验.     

一类不确定线性切换系统二次鲁棒稳定性的充分条件

本文研究了一类不确定线性切换系统的二次鲁棒稳定性问题.首先利用矩阵集的严格完备性设计切换律,导出了二次鲁棒稳定的充分条件.同时得到了在任意切换策略下,当矩阵集的所有矩阵为负定时保证切换系统二次鲁棒稳定性.在适当的假设下,这些条件可以表示为矩阵不等式.最后,用数值例子对所得结果加以阐明,说明了文中结果的正确性.     

一类稀疏效应下捕食-被捕食者系统极限环的存在性和唯一性

本文研究捕食者种群具有线性密度制约的一类稀疏效应下捕食－被捕食者系统ｘ＝ｘ（ａｘ－ｃｘ^３－ｂｙ），ｙ＝ｙ（－α＋βｘ－γｙ）．（＊）得到：（１）当Ａ_１＜Ａ_１，Ａ₂＜Ａ₂，Ａ₃＞Ａ₃时，系统（＊）在第一象限内存在极限环；（２）当Ａ₂＜Ａ₂，Ａ₃＞Ａ₃时，系统（＊）在第一