pH值和钙离子对尖吻蝮蛇抗血小板凝集素二级结构的影响

尖吻蝮蛇毒中抗血小板凝集素是凝血因子IX/凝血因子X结合蛋白，它具有抗凝血和抑制血小板凝集双重活性。用红外光谱、拉曼光谱和CD谱研究了抗血小板凝集素的二级结构以及pH值和钙离子对其二级结构的影响。用CD谱测得，在水溶液中，抗血小板凝集素的主要骨架构象为β-折叠(26.3%)和α-螺旋(19.6%)结构。拉曼光谱显示，在粉末状态，其α-螺旋含量显著降低。CD谱还表明，抗血小板凝集素在pH值3.0～11.0范围内保持稳定的天然结构，钙离子诱导的抗血小板凝集素结构变化是可逆的，钙离子在稳定抗血小板凝集素的天然结构中起重要作用。     

共振光散射法研究脱氧核糖核酸与多胺的相互作用及精胺的测定

在一定条件下,精胺不仅能够与脱氧核糖核酸(DNA)大沟嵌入结合,还能与DNA链上的碱基和磷酸基进行链内结合和跨链结合,形成致密的环状螺旋结构,造成DNA的凝聚,从而使DNA共振光散射(RLS)强度强烈地增强。增强的共振光散射强度与精胺的浓度呈现良好的线性关系,线性范围为5.0×10-7~1.0×10-5mol/L;校正曲线的回归方程为IRLS=40.22 5.28×107C(mol/L),相关系数r=0.9936;检出限(3σ)为7.4×10-8mol/L。在测定精胺的线性范围内,其它多胺(亚精胺,腐胺)、蛋白质及常见的金属离子不干扰测定。该方法用于测定新几内亚凤仙中的精胺,获得满意结果。     

金纳米微粒作探针共振瑞利散射光谱法测定亚甲蓝

在pH为6.5~9.5的中性或弱碱性介质中, 金纳米微粒可与亚甲蓝(MB)阳离子靠静电引力及疏水作用力结合, 形成粒径较大的聚集体(平均粒径从12 nm增至20 nm), 这种聚集体的形成导致共振瑞利散射(RRS)强度显著增强, 最大散射峰位于371 nm. 在适当条件下, 散射强度(ΔI)与亚甲蓝浓度成正比. 该法具有高灵敏度, 将金纳米微粒作为测定亚甲蓝的高灵敏RRS探针, 对亚甲蓝的检出限为21.17 ng/mL, 该法简便， 快速， 且有较好的选择性, 可用于血液中亚甲蓝的测定.     

Resonance Rayleigh scattering determination of trace amounts of Al in natural waters and biological samples based on the formation of an Al(III)-morin-surfactant complex

A novel method for the determination of trace amounts of Al(III) based on resonance Rayleigh scattering (RRS) has been developed. In the presence of some surfactants, Al(III) can react with morin and form an Al(III)-morin-surfactant complex, which results in the enhancement of RRS intensity and the appearance of the corresponding RRS spectral characteristics. Their maximum scatter peaks are at 476 nm for the cetyltrimethylammonium bromide (CTAB) system, 489 nm for the cetylpyridinium chloride (CPC) system, 474 nm for the Triton X-100 system, and 473 nm for the Tween-20 system. The enhanced RRS intensity is directly proportional to the concentration of Al(III). The detection limits are in the range of (0.50-1.2)×10⁻⁷ mol l⁻¹ depending on the surfactant. The characteristics of RRS spectra of the complexes, the optimum conditions of these reactions and the influencing factors have been investigated. The method has high selectivity, and was successfully applied to the determination of Al(III) in natural and biological samples. Furthermore, according to different complexation capacity of Al(III)-morin-CTAB system under two pH conditions, speciation analysis of Al(III) in natural waters was explored. The labile monomeric Al fraction (mainly inorganic Al, Al_i) is determined at acidic pH and the total monomeric Al fraction (Al_a) is determined at alkaline pH. The results are in agreement with those obtained by Driscoll’s 8-hydroxyquinoline extraction-ion exchange method.     

On the calculation of a limit for infinite systems from data on finite systems

We propose a mathematical model for the calculation of physical or chemical properties of infinite polymers, based on data for structurally closely related finite molecules. The modelling is phenomenological but permits a physical interpretation of the parameters involved in the equations. Received: 11 June 1996 / Accepted: 5 June 1997     

Triple Positive Solutions of Boundary Value Problems for High-order Fractional Differential Equation at Resonance with Singularities

In this paper, we investigate the existence of triple positive solutions of boundary value problems for high-order fractional differential equation at resonance with singularities by using the fixed point index theory and the Leggett-Williams theorem. The spectral theory and some new height functions are also employed to establish the existence of triple positive solutions. The nonlinearity involved is arbitrary fractional derivative, and permits singularity.     

The asymptotic behavior of queueing systems: Large deviations theory and dominant pole approximation

This paper presents the exact asymptotics of the steady state behavior of a broad class of single-node queueing systems. First we show that the asymptotic probability functions derived using large deviations theory are consistent (in a certain sense) with the result using dominant pole approximations. Then we present an exact asymptotic formula for the cumulative probability function of the queue occupancy and relate it to the cell loss ratio, an important performance measure for service systems such as ATM networks. The analysis relies on a new generalization of the Taylor coefficients of a complex function which we call characteristic coefficients. Finally we apply our framework to obtain new results for the M/D/1 system and for a more intricate multiclass M/D/n system.     

罗丹明6G与核酸作用的共振光散射光谱及其分析应用

研究了罗丹明6G（Rh6G）与核酸（ctDNA和yRNA)作用的共振光散光谱（RLS）特征，基于RLS的增强，建立了一种测定核酸的新方法，考察了各种影响因素，在优化条件下确定了RLS强度与ctDNA和yRNA浓度之间的关系，相应的线性范围分别为0.05-37.0μg.mL^-1、0．1－10．0μg.mL^-1，检出限分别为3．0ng.mL^-1和9．5ng.mL^-1。四种合成样品五次平行测定结果的相对标准偏差（RSD）范围为2．0％－3．0％。     

Non-covalent assemblies of negatively charged boronated porphyrins with different cationic moieties

A unique approach to non-covalent electron and energy transfer is described that is based on the formation of salt bridges between oppositely charged porphyrin units. A new class of electrostatically linked dimeric and pentameric porphyrins was synthesized by interaction of novel anionic boron containing porphyrins such as 5-(benzamidodecahydro-closo-dodecaborate)-10,15,20-triphenylporphyrin (N1) and meso-tetrakis-benzamidodecahydro-closo-dodecaborate)porphyrin (N2) and a variety of cationic meso-tetraarylporphyrin units. A bipyridine linked dimer (N1 · bpy · N1) was also prepared by employing N,N′-dimethyl-4,4′-bipyridinium (bpy) as a spacer between two mono-anionic species. A quinone-porphyrin dyad was also prepared for electron or energy transfer demonstration. All the synthesized assemblies were characterized by NMR, IR, UV-Vis, and mass spectroscopy. Significant spectral changes occurred in the absorption spectra of these non-covalent porphyrin assemblies compared to those of the reference monomers, indicating the presence of electronic interaction between the adjacent porphyrin units. Resonance light scattering was also used to study the formation of these assemblies in solution.     

夜蓝共振瑞利散射光谱法测定透明质酸钠

在pH3．0～3．9的HAc—NaAc介质中，夜蓝与透明质酸钠作用形成结合产物时将导致溶液共振瑞利散射(RRS)增强，并产生新的RRS光谱，其最大散射峰位于408nm处。透明质酸钠在0～1．5mg／L范围内其浓度与RRS强度成正比。据此，建立了一种测定透明质酸钠的新方法。该法对透明质酸钠的检出限(3d)为13．7μg／L。应用于润舒氯霉素滴眼液和润洁滴眼露中透明质酸钠的测定，回收率在98．2％～104．3％之间，结果满意。