类水滑石主体层板与客体CO2-3、H2O间的超分子作用

通过构建类水滑石双层计算模型, 采用混合密度泛函B3LYP/6-31G(d)//B3LYP/3-21G方法计算类水滑石(LDHs-CO3-yH2O)的结构与能量, 探讨LDHs限域空间中客体阴离子及水分子的分布形态以及主客体超分子作用. 计算结果表明, 客体阴离子与水分子以平行层板的方式存在于水滑石层间. 主客体发生作用时, CO2-3的HOMO轨道向层板的LUMO轨道转移电子. 所形成的LDHs-CO3主客体作用要强于LDHs-F以及LDHs-Cl, 与其离子交换性能相一致. 水滑石去水结构(LDHs-CO3)水合过程, 氢键作用较静电作用更占优势, 并且layer-water型氢键要强于anion-water 型氢键. 此外, 水合能计算表明LDHs水合具有一定的饱和量.     

Atomistic modelling of the hydration of CaSO4

Atomistic modelling techniques, using empirical potentials, have been used to simulate a range of structures formed by the hydration of γ-CaSO₄ and described as CaSO₄·nH₂O (0<n<1). The hemihydrate phase (n=0.5) is of commercial importance and has been subjected to much experimental study. These simulation studies demonstrate significant water-matrix interactions that influence the crystallography of the hydrated phase. The existence of two types of hydration site has been predicted, including one within the Ca²⁺coordination sphere. Close correlation between water molecule bonding energy, Ca²⁺-O_w bond length and unit-cell volume have been established. This shows that as the number of water molecules within the unit cell increases, the bonding energy increases and the unit cell contracts. However around n=0.5, this process reaches a turning point with the incorporation of further waters resulting in reduced binding energy and an expanding unit cell.     

水合和pH对蛋白酶K热诱发转变影响的量热法研究

用差示扫描量热法, 在310～450 K温度范围、0.048～4.39克水/克干酶以及pH3～9范围内研究了蛋白酶K(EC 3.4.21.14)的热变性。分别提出表征热变性过程的三个主要热力学参数: 热变性温度T_d、比变性焓△H_d及超额表观比热C_(ex)~(max)和总水量h以及pH的关系。除Td和h的关系属于Flory-Garrett类型外, 蛋白酶K的热变性热力学特征和已报道的球蛋白、双螺旋蛋白及三螺旋蛋白不相同。一级水合水对蛋白酶K热变性热力学特征有最大的影响, pH也是影响该酶热稳定性的重要因素。     

Study of Host-Guest Complexation of Alkaline Earth Metal Ion,Aluminum Ion and Transition Metal Ions with Crown Ethers by Fast Atom Bombardment Mass Spectrometry

Complexations of crown ethers with alkali metal ions have been investigated extensively by FAB mass spectrometry over the past decade, but very little attention has been paid to reactions of crown ethers with other classes of metal ions such as alkaline earth metal ions, transition metal ions and aluminum ions. Although fast atom bombardment ionization mass spectrometry has proven to be a rapid and convenient method to determine the binding interactions of crown ethers with metal ions, problems in reliabilities for quantitative measurements of” binding strength for the host-guest complexes have been described in the literature. Thus, in this paper, applications of FAB/MS for investigating the complexation of crown ethers with various classes of metal ions is discussed. Extensive fragmentations for neutral losses such as C₂H₄O or C₂H₄ molecules from the host-guest complexes could be observed. The reason is attributed to the energetic bombardment processes of FAB occuring in the formation of these complexes. Complexes of cyclen with metal ions also show neutral losses of C₂H₄NH molecules leading to fragment ions. Transition metal ions usually form (Crown + MCl)⁺ type of ions, alkaline earth metal ions can form both (Crown + MCl)⁺ and (Crown + MOH)⁺ type of ions. But for aluminum ions, only (Crown + Al(OH)₂)⁺ type of ions could he observed.     

Thermal decomposition of HfCl4 as a function of its hydration state

The thermogravimetric behavior of HfCl₄ powders with different hydration states has been compared. Strongly hydrated powders consist of HfOCl₂·nH₂O with n>4. Partially hydrated powders consist of particles with a HfCl₄ core and a hydrated outerlayer of HfOCl₂·nH₂O with n in the range of 0-8. Hydrated powders decomposed at temperature lower than 200 °C whereas the decomposition of partially hydrated powders was completed at a temperature of around 450 °C. The observed differences in decomposition temperature is related to the structure of HfOCl₂·nH₂O, which is different if n is higher or smaller than 4 and leads to intermediate compounds, which decompose at different temperatures.     

Theoretical study of the calcium dication hydrates

Ab initio SCF calculations have been carried out for calcium dication surrounded by 1–4 or 6 water molecules using several basis sets. The structure of the hydrated ions is examined and the hydration energy estimated. The changes in the structure of water within the complex are qualitatively explained in terms of charge transfer and coulombic interactions among the atoms. Finally, the influence of electron correlations is discussed.     

The stokes and robinson hydration theory: A modification with application to concentrated electrolyte solutions

The proposed extension to the Stokes and Robinson hydration theory is based on the premise that H₂O molecules of electrolyte solutions reside in two unique environments, the solvent environment and the hydration envelope (or sheath) environment. Changes to the chemical potential of H₂O in either environment result in redistribution of H₂O molecules between the environments; consequently hydration numbers of electrolytes decrease as the solvent activity decreases. An equation derived from the theory and containing two adjustable parameters reproduces electrolyte activity coefficients more accurately than does the original Stokes and Robinson equation.     

Collagen absorption bands in heated and rehydrated dentine

The objective of this work is identifying changes in the collagen bands in heated and rehydrated dentine. We use bovine dentine slices that were heated in oven between 100 and 300 degrees C. The sample hydration was conducted in sodium chloride solution at 0.9 wt.%; the spectra were acquired by a Fourier transform infrared spectrometer in the spectral range of 4000-400 cm-1. Our results show a temperature range (T225 degrees C) where the collagen is denatured and no reversion is observed after rehydration. This work identifies an important characteristic that dentinal collagen can assume when the tissue is heated and rehydrated; these results indicate the denaturation temperature of dentinal collagen to be near 175-200 degrees C.     

水化Na-蒙脱石和Na/Mg-蒙脱石的分子动力学模拟

利用分子动力学方法(MD)研究了Na-蒙脱石和Na/Mg-蒙脱石层间的补偿阳离子和水分子的结构及扩散性质. 模拟结果表明, 在一定水含量范围内Na-蒙脱石和Na/Mg-蒙脱石表现出不同的膨胀形式, 特别是层间水分子数目在48～72之间时, Na/Mg-蒙脱石的层间距比Na-蒙脱石有较为明显的增大. Na/Mg-蒙脱石两层水化物的层间水分子与Mg2+形成了明显的两层水合壳; 而与Na+只形成了一层平面的水合壳. 在Na/Mg-蒙脱石中, Na+和 Mg2+的扩散方式不同, Na+的扩散范围相对更广, 自扩散系数更大. Na/Mg-蒙脱石比相同水含量下的Na-蒙脱石层间水的自扩散系数小. 由于Mg2+和Na+对层间结构的强烈影响, 从而使有少量Mg2+取代Na+的Na/Mg-蒙脱石与Na-蒙脱石表现出不同的膨胀性质和层间物质的扩散性质.     

The influence of Na+ on neighbouring hydrogen bonds of aliphatic amino acid

Summary The influence of Na⁺ on hydrogen bonds of the OH O and NH O type between an aliphatic amino acid (glycine zwitterion) and water is investigated byab initio calculations with minimal Gaussian basis sets. Distortion of the hydration shell caused by Na⁺, and interaction energies contributing to the over-all stabilization are discussed.

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Der Einfluß von Na⁺ auf die benachbarten Wasserstoffbindungen in aliphatischen Aminosäuren

Zusammenfassung Der Einfluß von Na⁺ auf die Wasserstoffbindungen vom OH O- und NH O-Typ in aliphatischen Aminosäuren (Glycin-Zwitterion) und Wasser wurde mittelsab initio Berechnungen mit einem minimalen Gausschen Basissatz untersucht. Die durch Na⁺-Ionen hervorgerufenen Verzerrungen der Hydratationsschale und die zur Gesamtstabilisierung beitragenden Wechselwir-kungsenergien werden diskutiert.