Interaction of hen egg white lysozyme with cefpiramide sodium: multi-spectroscopic and computational simulations

Abstract

Under simulated physiological conditions (pH?=?7.40), the interaction between cefpiramide sodium and hen egg white lysozyme was studied with multi-spectroscopy and molecular docking. The results showed that cefpiramide sodium quenched the fluorescence of hen egg white lysozyme by static quenching, and the number of binding site n was about 1. The binding distance (r) between cefpiramide sodium and hen egg white lysozyme was obtained based on the Förster nonradioactive resonance energy transfer and r was less than 7?nm, which indicated that there was a non-radiative energy transition in the system. The thermodynamic parameters were obtained from the van't Hoff equation, and the Gibbs free energy ΔG?H?S?>?0, indicating hydrophobic interaction played a major role in forming the cefpiramide sodium-hen egg white lysozyme complex. Synchronous spectra, circular dichroism spectra and UV-Vis spectra showed that cefpiramide sodium changed the conformation of hen egg white lysozyme. The molecular docking results showed that the binding position of cefpiramide sodium was close to the active center composed of Asp52 and Glu35 residues, suggesting that cefpiramide sodium could change the microenvironment of amino acid residues at the catalytic active center of hen egg white lysozyme.     

基于“猫眼”效应的激光侦察技术及其在军事上的应用

光电设备或光学观瞄设备的光学窗口对入射激光具有较强的反射特性,该特性也被称为"猫眼"效应。从理论上分析了猫眼效应产生的机理,并将理论计算结果与实验结果进行了比较。论述了基于猫眼效应的激光侦察技术原理和该技术在军事上的应用。讨论了影响猫眼效应的因素,并用实验结果证明了理论分析得出的部分结论。     

Spectrophotometric studies on the interaction between myricetin and lysozyme in the absence or presence of Cuor Fe

The binding of myricetin to lysozyme (Lys) in aqueous solution was investigated by fluorescence spectroscopy, ultraviolet-visible absorption spectroscopy (UV) and circular dichroism (CD) spectra under physiological conditions. There are also many metal ions present in body, thus the research about the effect of metal ions on the interaction of drugs with proteins is crucial. In this study, we have investigated the effect of both familiar metal ions Cu²⁺ and Fe³⁺ on the interaction between myricetin and Lys by using spectroscopy technique at pH 7.40, for the first time. Spectrophotometric observations are rationalized in terms of a static quenching process in a static quenching way. The cause of showing upward curvy patterns in Stern-Volmer plots was analyzed. The binding constants and binding sites of myricetin with Lys with or without Cu²⁺ and Fe³⁺ at different concentrations of myricetin were calculated. UV/vis measurements on the enzymatic activity of Lys with or without Cu²⁺ in the absence or presence of myricetin indicated that the interaction between myricetin and Lys led to a reduction in the activity of Lys. Furthermore, the effect of pH on the binding constant of myricetin with Lys was also examined.     

Fluorescence spectrometric studies on the binding of puerarin to human serum albumin using warfarin, ibuprofen and digitoxin as site markers with the aid of chemometrics

The interaction of puerarin with human serum albumin (HSA) in pH 7.4 Tris-HCl buffer has been investigated by fluorescence, Fourier transform infrared (FT-IR) and circular dichroism (CD) spectroscopy. The results revealed the presence of static type of quenching mechanism in the binding of puerarin to HSA. The association constants (K_a) between puerarin and HSA were obtained according to Modified Stern-Volmer equation. The calculated thermodynamic parameters indicated that the binding of puerarin to HSA was driven mainly by hydrophobic interaction. The competitive experiments of site markers suggested that the binding site of puerarin to HSA was located in the region of subdomain IIA (sudlow site I). Further, a chemometrics approach, parallel factor analysis (PARAFAC), was applied to resolve the measured three-way synchronous fluorescence spectra data of the competitive interaction between puerarin and warfarin with HSA. The concentration information for the three reaction components, warfarin, puerarin and puerarin−HSA, in the system at equilibrium was obtained simultaneously. The PARAFAC analysis indicated that puerarin in the puerarin-HSA complex was displaced by warfarin, which confirmed the binding site of puerarin to HSA was located in site I. Moreover, the results of CD and FT-IR spectra demonstrated that the secondary structure of HSA was changed in the presence of puerarin.     

国际液晶学会与活性行走的由来

国际液晶学会是作者于1990年建议成立的，活性行走的概念是作者于1992年提出的．活性行走是描述简单与复杂系统中自组织和图样形成的一个范式，已被广泛应用于自然科学和社会科学的各种系统中．文章首次给出关于国际液晶学会与活性行走创立过程的第一手资料，并介绍了活性行走的实质和意义．     

The size of active bubbles for the production of hydrogen in sonochemical reaction field

The sonication of aqueous solution generates microscopic cavitation bubbles that may growth and violently collapse to produce highly reactive species (i.e. OH, HO₂ and H₂O₂), hydrogen and emit light, sonoluminescence. The bubble size is a key parameter that influences the chemical activity of the system. This wok aims to study theoretically the size of active bubbles for the production of hydrogen in ultrasonic cavitation field in water using a single bubble sonochemistry model. The effect of several parameters such as frequency of ultrasound, acoustic intensity and liquid temperature on the range of sonochemically active bubbles for the production of hydrogen was clarified. The numerical simulation results showed that the size of active bubbles is an interval which includes an optimum value at which the production rate of H₂ is maximal. It was shown that the range of ambient radius for an active bubble as well as the optimum bubble radius for the production of hydrogen increased with increasing acoustic intensity and decreased with increasing ultrasound frequency and bulk liquid temperature. It was found that the range of ambient bubble radius dependence of the operational conditions followed the same trend as those reported experimentally for sonoluminescing bubbles. Comparison with literature data showed a good agreement between the theoretical determined optimum bubble sizes for the production of hydrogen and the experimental reported sizes for sonoluminescing bubbles.     

Optimization of the number and the positions of error sensors in adaptive active sound control

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Alloying effects and site occupancies of Re in the C14 Cr-based Laves phases: a first-principles study

First-principles calculations based upon the density functional theory have been carried out to investigate the alloying effects and site occupancies of Re in the C14 XCr₂ (X?=?Nb, Ta, Ti, Zr, Hf) Laves phases. The calculated results indicate that Re tends to facilitate and participate in the formation of the Laves phases, generating X₈Cr₁₅Re accordingly. The partial density of states and charge density di?erence were analysed to re?ect the bonding characteristics. For X₈Cr₁₅Re, the bonding between the doped Re and its nearest neighbour Cr atoms all show covalent characteristics, which contribute to the phase stability. The substitution of Re on X sites is energetically unfavourable due to the weak bonding between Re and its nearest neighbour X atoms.     

Difference in radiocarbon ages of carbonized material from the inner and outer surfaces of pottery from a wetland archaeological site

AMS (Accelerator Mass Spectrometry) radiocarbon dates for eight potsherds from a single piece of pottery from a wetland archaeological site indicated that charred material from the inner pottery surfaces (5052 ± 12 BP; N = 5) is about 90 (14)C years older than that from the outer surfaces (4961 ± 22 BP; N = 7). We considered three possible causes of this difference: the old wood effect, reservoir effects, and diagenesis. We concluded that differences in the radiocarbon ages between materials from the inner and outer surfaces of the same pot were caused either by the freshwater reservoir effect or by diagenesis. Moreover, we found that the radiocarbon ages of carbonized material on outer surfaces (soot) of pottery from other wetland archaeological sites were the same as the ages of material on inner surfaces (charred food) of the same pot within error, suggesting absence of freshwater reservoir effect or diagenesis.     

Period-doubling bifurcation in two-stage power factor correction converters using the method of incremental harmonic balance and Floquet theory

In this paper, period-doubling bifurcation in a two-stage power factor correction converter is analyzed by using the method of incremental harmonic balance (IHB) and Floquet theory. A two-stage power factor correction converter typically employs a cascade configuration of a pre-regulator boost power factor correction converter with average current mode control to achieve a near unity power factor and a tightly regulated post-regulator DC-DC Buck converter with voltage feedback control to regulate the output voltage. Based on the assumption that the tightly regulated post-regulator DC-DC Buck converter is represented as a constant power sink and some other assumptions, the simplified model of the two-stage power factor correction converter is derived and its approximate periodic solution is calculated by the method of IHB. And then, the stability of the system is investigated by using Floquet theory and the stable boundaries are presented on the selected parameter spaces. Finally, some experimental results are given to confirm the effectiveness of the theoretical analysis.     

Hf-N体系的晶体结构预测和性质的第一性原理研究

为了寻找具有优异力学性能的新型超高温陶瓷材料, 结合进化算法和第一性原理, 系统研究了Hf-N二元体系所有稳定存在的化合物及其晶体结构. 除了实验已知的岩盐结构的HfN之外, 本文还找到了Hf₆N(R-3), Hf₃N(P6₃22), Hf₃N₂(R-3m), Hf₅N₆(C2/m)和Hf₃N₄(C2/m)五种新结构, 基于准简谐近似原理计算了这些稳定结构的声子谱以验证其动力学稳定性, 常温甚至更高温度下的吉布斯自由能以验证其高温热力学稳定性. 结果表明, 这些结构是动力学稳定的, 且在1500 K以下都是热力学稳定的. 同时, 本文还列出了在搜索过程中出现的空间对称性较高、能量较低的亚稳态结构, 包括Hf₂N(P4₂/mnm), Hf₄N₃(C2/m), Hf₆N₅(C2/m), Hf₄N₅(I4/m), Hf₃N₄(I-43d)和Hf₃N₄(Pnma). 之后计算了上述所有结构的力学性质(弹性常数、体模量、 剪切模量、 杨氏模量、硬度), 随着N 所占比例的增加, 硬度呈现的整体趋势是先增大后下降, 在Hf₅N₆处取得最大值, 为21 GPa. 其中Hf₃N₂和Hf₄N₅也展现出了较高的硬度, 都为19 GPa. 最后, 计算了这些结构的电子态密度和晶体轨道汉密尔顿分布, 从电子结构的角度分析了力学性能的成因. 研究结果显示, 较强的Hf-N共价键和较低的结构空位率是Hf₅N₆具有优异力学性能的主要原因.     

The Excitation Temperatures of Nonmetal Atoms and the OH Temperatures in Microwave-Induced Plasma

Abstract

The excitation temperatures of nonmetal atoms and the OH molecule temperatures have been measured in argon MIP, operating under atmospheric pressure at different experimental conditions. Atoms of Ar I, P I and H have been used as thermometric species. The rotational and vibrational temperatures have been obtained from the OH A²Σ⁺ - X²? band spectra. The ^SR₂₁ ratational lines have been used for the first time for the temperature measurements. The energy distributions observed here are discussed.     

嵌入原子法研究Ni3Al中点缺陷以及Re择优占位和集团化

基于纯金属元素Ni，Al和Re的基本物理性质，建立了一个Ni-Al-Re三元体系的分析型嵌入原子多体势.结合分子动力学计算了Ni₃Al的平衡晶格常数、弹性模量、结合能、空位形成能以及反位置缺陷形成能，并分析了Ni₃Al中点缺陷的存在形式.计算结果表明，当成分偏离理想化学配比时出现反位置缺陷.同时研究了Re在Ni₃Al中的择优占位以及Re在Ni₃Al和Ni中的集团化行为.计算结果表明，Re在Ni₃Al中优先置换Al的位置，且发现当Re原子团的尺寸接近于11?时，Re原子团的长大趋势变弱.计算结果与实验以及其他的理论计算结果相符合. 关键词： 嵌入原子势 3Al')" href="#">Ni₃Al Re 占位 集团化     

Effect of glutaphen on generation of active oxygen species, photosynthetic electron transport, and the functional activity of photosystem 2 in Chlorella cells

Treatment of chlorella green algae (Chlorella sp.) for 2 h in the dark with the photodynamic herbicide glutaphen (GTP), consisting of 0.3 mM 1,10-phenanthroline and 0.6 mM glutamic acid, followed by illumination leads to efficient generation of active oxygen species (AOS). After 15 min of illumination, AOS accumulation reaches 200% compared with the level in cells of the control culture, then it decreases down to 130% and 115% after 1 day and 3 days of illumination. During the first few days after treatment, we observe inhibition of synthesis of a specific precursor of chlorophyll (Chl): 5-aminolevulinic acid molecules, and then we observe stimulation of the synthesis. The effect of GTP on the photosynthetic activity of chlorella does not depend on the AOS level but rather remains uniform, in contrast to its effect on the Chl biosynthesis system. GTP does not change the efficiency of light harvesting and charge separation at the reaction centers of photosystem (PS) 2, but significantly lowers the functional efficiency of the electron transport chain: the photochemical quenching constants for Chl a fluorescence and the effective quantum yield of photochemical reactions in photosystem 2 decrease. The major mechanism of action for GTP is probably displacement of the secondary quinone acceptor Q_B from its binding site on the D1 protein by the 1,10-phenanthroline, consequent inhibition of electron efflux from Q _A ⁻ and increase in the fraction of Q_B-nonreducing centers of PS 2. The active oxygen species generated in the cells have a photodegradative effect on the Chl biosynthesis system, in particular on its initial steps, and do not involve already formed pigment-protein complexes of PS 2. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 6, pp. 801–806, November–December, 2006.     

大型粮仓温度分布反演数学模型的研究

采用有限元数值模拟方法,以响应面模型RSM(Response surface model)理论为基础对大型粮仓冬、夏两季的温度分布进行了深入分析,推导了粮仓温度反演数学模型。将采集的温度值导入RSM模型中,并结合单因素轮换法、正交实验和统计方法,通过构造一个具有明确表达形式的多项式来预测粮仓温度分布反演数学模型。在数学模型的基础上给出各因子交互作用下的设计空间、各因素对粮温影响的主效应及交互效应。实验证明该数学模型误差小,精度高,具有良好的计算性能,在大型粮仓温度监控系统中采用该模型能够解决布线少、预测空间范围广的问题。     

美国激光制导武器的发展现状与趋势

文章重点介绍了激光制导的原理和方式,同时用几种典型的激光制导武器说明了美国在此方面的发展,对激光武器的优缺点及其发展趋势也作出了深刻的分析.     

交流阻抗及功率因数测量中偏差的修正

介绍了在交流阻抗及功率因数测量中由测量仪表引起的偏差的修正方法.主要讨论了一级修正和精确修正两种方法,导出了计算复阻抗和功率因数的修正式.给出了测量日光灯电路的阻抗及功率因数的实例.由计算结果可以看出,精确修正后的结果与不做修正的结果之间存在较大的差异,说明在要求较精确测量的情况下,应该对测量结果进行修正.