Anti-microbial Activities of Protic Ionic Liquids Studied with Microcalorimetry Method

The anti-microbial activities of seven protic ionic liquids(ILs) against Escherichia coli and Staphylococcus aureus were studied by a micro-calorimetric method at 310 K.The bacterial growth rate constants were determined based on the bacterial growth power-time curves,andminimum biocidal concentrations were estimated.The results indicate that the protic ILs studied show inhibitory activities on the bacteria,implying a potential eco-toxicity to the microorganisms in the water system.Moreover,the inhibition e...     

Binding and degradation of DNA on montmorillonite coated by hydroxyl aluminum species

Adsorption, desorption and degradation by DNase I of DNA on montmorillonite (M) and different hydroxyaluminum-M complexes (Al(OH)_x-M) containing 2.5, 10.0 and 20.0 mmol coated Al/g clay (AM_2.5, AM₁₀ and AM₂₀) were studied. The adsorption isotherms of DNA on montmorillonite and Al(OH)_x-M complexes conformed to the Langmuir equation. The amount of DNA adsorbed followed the sequence of montmorillonite > AM₂₀ > AM₁₀ > AM_2.5. A marked decrease in the adsorption of DNA on montmorillonite and Al(OH)_x-M complexes was observed with the increase of pH from 4.0 to 9.0. Calcium ion significantly promoted DNA adsorption. The adsorption enthalpy of DNA on montmorillonite was endothermic, whereas that on Al(OH)_x-M complexes was exothermic. The percent desorption of DNA from clays was in the order of montmorillonite > AM_2.5 > AM₁₀ > AM₂₀, suggesting that OH–Al loading on montmorillonite surface increased the binding affinity of DNA. Fourier transform infrared (FTIR) spectra showed that the binding of DNA on AM₁₀ and AM₂₀ changed its conformation from the B-form to the Z-form. The presence of montmorillonite and Al(OH)_x-M complexes provided protection for DNA against degradation by DNase I. The higher level of protection was found with Al(OH)_x-M complexes compared to montmorillonite. The higher stability of DNA in the system of Al(OH)_x-M complexes seemed to be attributed mainly to the conformational change of bound DNA and their greater adsorption capacity for DNase I. The information obtained in this study is of fundamental significance for understanding the behavior of extracellular DNA in soil environments.     

MnMoO4·H2O纳米棒生长过程的原位热动力学研究

在298.15 K下采用现代微量热技术监测了微乳液法原位合成MnMoO4·H2O纳米棒过程中能量变化的微量热曲线. 该曲线显示, 反应开始瞬时放热, 有一个尖锐的放热峰, 在随后的过程中分别出现一个强的吸热峰和放热峰. 通过X射线粉末衍射仪(XRD)、 场发射扫描电子显微镜(FESEM)和透射电子显微镜(TEM)等对MnMoO4·H2O纳米棒的结构、 形貌及尺寸进行了表征. 结合微乳液的特性和量热曲线, 讨论了MnMoO4·H2O纳米棒生长过程中的形貌演变和热动力学信息. 整个生长过程包含微乳液的碰撞凝聚、 反应成核、 结晶和生长过程. 经计算, 反应成核过程、 晶化过程及晶体二次生长过程的速率常数分别为6.35×10-3, 7.18×10-4和9.16×10-5 s-1. 生长速率小于成核速率, 这有利于纳米材料的形成.     

环丙沙星与牛血清白蛋白的结合反应

以光谱技术与微量热技术相结合研究了水溶液中牛血清白蛋白与环丙沙星分子间结合作用的机制. 荧光猝灭法测得该反应的结合常数K=8.39×104 L•mol－1,结合位点数n =1.18;依据Fōrster非辐射能量转移机制,得到授体 受体间的结合距离(r=2.46 nm)和能量转移效率(E=0.33).微量热法测得反应的焓变 ΔrHm≈0;牛血清白蛋白与环丙沙星分子间有较强的结合作用,且以疏水作用为主.     

细菌变异株生长热谱研究

用微量热法研究微生物的生长与代谢,是生物热力学一个新的研究领域.我们已经测得细菌生长的完整热谱,这种热谱具有良好的重现性和明显的特征性,可以作为细菌的“指纹图”对其进行种的分类和鉴定[1～5].但在研究中发现,同种细菌不同变异株的生长图谱略有差异,若培养基选择?..     

微量热法研究漆酶和3,4,5-三羟基苯甲酸的反应

用LKB－2107型微量热系统,在不同的温度(pH＝7.4)条件下,测定了3,4,5－三羟基苯甲酸与漆酶反应的摩尔反应烙、米氏常数、反应速率常数、漆酶的活性并计算了结合能、活化自由能、活化能和活化烟等.在此基础上,应用过渡态理论,从能量变化的角度,对其催化过程进行了分析.由活化摘(△S_≠^T＜0)得出酶－底物过渡态的结构较酶－底物复合物更为有序的结论.     

Entropic Contributions to Sodium Solvation and Solvent Stabilization upon Electrochemical Sodium Deposition from Diglyme and Propylene Carbonate Electrolytes

The formation of an appropriate solid electrolyte interphase (SEI) at the anode of a sodium battery is crucially dependent on the electrochemical stability of solvent and electrolyte at the redox potential of Na/Na⁺ in the respective system. In order to determine entropic contributions to the relative stability of the electrolyte solution, we measure the reaction entropy of Na metal deposition for diglyme (DG) and propylene carbonate (PC) based electrolyte solutions by electrochemical microcalorimetry at single electrodes. We found a large positive reaction entropy for Na⁺ deposition in DG of Δ_R 234 J mol⁻¹ K⁻¹ (c.f.: Δ_R 83 J mol⁻¹ K⁻¹), which signals substantial entropic destabilization of Na⁺ in DG by about 0.73 eV, thus increasing the stability of solvent and electrolyte relative to Na⁺ reduction. We attribute this strong entropic destabilization to a highly negative solvation entropy of Na⁺, due to the low dielectric constant and high freezing entropy of DG.