离子液体对木瓜蛋白酶催化特性的影响

研究了以1-丁基-3-甲基咪唑、四乙基铵及N-乙基吡啶为阳离子, 配以多种阴离子(H₂PO₄^-, ClO₄^-, HSO₄^-, CH₃COO^-, Cl^-, Br^-, NO₃^-, SCN^-, BF₄^-, PF₆^-)的离子液体对木瓜蛋白酶催化N-苯甲酰-L-精氨酸乙酯(BAEE)水解的活性及热稳定性的影响. 通过分析含离子液体体系中木瓜蛋白酶的水解活性和热力学失活参数, 发现该酶活性及稳定性与离子液体的Kosmotropicity性质无关. 因此, 离子的Hofmeister效应并不适合解释离子液体对木瓜蛋白酶催化特性的影响规律. 当以BF₄^-为阴离子, 改变阳离子结构时, 仅[BMIm][BF₄]可提高酶活性, 其它含官能团的咪唑类离子液体则降低酶活性, 但大部分离子液体明显提高木瓜蛋白酶的热稳定性. 在所研究的离子液体中, 基于PF₆^-或BF₄^-阴离子的离子液体可提高木瓜蛋白酶的活性及其热稳定性. 在含[BMIm][PF₆]介质中, 木瓜蛋白酶的水解活性最高; 在含[HOEtMIm][BF₄]介质中其热稳定性最好.     

离子对水的17O-NMR化学位移和水结构的影响

在小于1 mol•L-1的浓度范围内,测试了碱金属、碱土金属氯化物、卤化钠及其它常见含氧酸盐溶液的17O-NMR化学位移（δ(H217O)）.发现离子对δ(H217O)的影响与离子的半径、电荷、离子外层电子结构及离子结构有关.其它离子参数相同时,离子半径越大,离子的摩尔δ(H217O)越大;在电子结构相同的情况下,离子电荷越大,离子的摩尔δ(H217O)越大;多原子离子的摩尔δ(H217O)更多地是与其离子结构相关.离子的摩尔δ(H217O)的大小反映了该离子对水的结构的影响情况,离子的摩尔δ(H217O)越大,对水的结构促进作用越强.     

阴离子对水的羟基伸缩振动拉曼光谱的影响

通过比较纯水、NaX(X=F, Cl, Br, I)、Na2S、NaOH、NaNO3、Na2CO3、Na2SO4溶液的羟基伸缩振动拉曼光谱, 发现所研究的阴离子对水的结构都有破坏作用. 通过比较阴离子对水的羟基伸缩振动拉曼光谱的影响, 可将所研究的阴离子分为两类, 一类阴离子有F−、OH−、S2−、CO32−, 另一类阴离子有Cl−、Br−、I−、NO3−和SO42−. 它们的主要区别在于对羟基伸缩振动拉曼光谱3600 cm−1、2900−3100 cm−1处影响不同, 产生这些区别的原因在于阴离子与水分子之间氢键的强弱. 阴离子对水的羟基伸缩振动拉曼光谱的影响因素有离子半径、离子电荷和离子结构, 它们的影响程度为离子结构>离子电荷>离子半径.     

Hofmeister效应辅助的蛋白质基水凝胶应变传感器

以酪蛋白酸钠和明胶为原料, 通过简单的在硫酸铵溶液中浸泡的方法, 借助Hofmeister效应制备了一种强韧导电的酪蛋白酸钠/明胶水凝胶, 克服了蛋白质基水凝胶柔软、 易碎的问题. 测试结果表明, 该水凝胶具有优异的机械性能, 最大拉伸应力为3.55 MPa, 最大拉伸应变为1375%; 水凝胶的最大电导率为0.0954 S/cm, 导电灵敏因子为0.53. 用该水凝胶制备的传感器对不同大小及不同速率的应变均具有分辨能力, 能够监测人体不同部位的运动, 且传感器的信号传输具有稳定性和准确性, 表明该水凝胶是监测人体健康和运动的理想材料. 该水凝胶还具有良好的形状记忆性能. 这一策略为制备全天然蛋白质基水凝胶开辟了新的思路, 扩展了水凝胶在生物医学和电子传感等相关领域的应用前景.     

烷基咪唑离子液体对脂肪酶催化酯水解反应活性的影响

考察了1-烷基-3-甲基咪唑类离子液体对柱状假丝酵母脂肪酶(CRL)催化橄榄油水解反应活性的影响,利用电导法确定了磷酸盐缓冲液中Br^-,Cl^-,[BF₄]^-系列咪唑离子液体的临界胶束浓度(CMC)和[PF₆]^-系列咪唑离子液体的溶解度.结果显示,离子液体的阴、阳离子对酶活性的影响规律与离子液体的Kosmotropicity性质无明显关联,但与离子液体在体系中的含量密切相关,在最适离子液体含量时,酶活性达到最高;阳离子[C_nMIM]⁺中的n越大,可促进酶活性的离子液体适宜含量越低;Br^-,[BF₄]^-系列离子液体的浓度超过CMC时则抑制酶活;阴离子对酶活性的最大促进作用顺序为Br^->Cl^->[BF₄]^->[PF₆]^-.离子液体对酶活性的影响随体系pH和温度的不同而改变,在最适离子液体浓度时的最适pH均为7.000.在pH 7.000,30 ^oC以及[C₈MIM]Br离子液体浓度为47.6 mmol/L的最佳条件下,最高相对酶活力和比活力分别达到1734%和54.4 U/mg protein.     

Hofmeister效应对生物和化学体系的影响

Hofmeister效应涉及到的问题范围十分广泛,对很多化学、生物体系都有影响。总的说来,Hofmeister效应会影响到溶液的冰点、沸点、黏度、偏摩尔体积、饱和蒸汽压、传导率、pH、表面张力。文章主要介绍了Hofmeister效应的主要影响因素,以及相关理论的建立与完善,并对不同体系中Hofmeister效应的影响进行了描述。     

拉曼光谱研究CaCl2和MgCl2对水结构的影响

测试了CaCl2、MgCl2溶液(浓度小于1.0 mol•L-1)的OH伸缩振动区域的拉曼光谱.对所得到的拉曼光谱进行了计算机去卷积处理,并由此计算了不同溶液中水的四面体结构的百分数.研究表明,CaCl2、MgCl2对水中四面体结构有破坏作用，且CaCl2的破坏作用比MgCl2大.与17O核磁共振结果对比与分析,认为CaCl2、MgCl2虽然破坏水中的四面体结构,但通过促进含氢键数少的水分子形成氢键,故从总体上促进水的缔合结构.     

离子对液态水缔合构造影响的能量表征

利用差示扫描量热法（DSC）,从能量变化的角度研究了在0-1.0 mol·L^-1浓度范围内,KCl、MgCl₂与CaCl₂对液态水缔合构造的影响,并与¹⁷O-NMR化学位移δ(¹⁷OH₂)的分析结果进行比较.随KCl、MgCl₂与CaCl₂浓度的升高,液态水的δ(¹⁷OH₂)呈线性增加,而表观活化能（-E’/R）呈线性减小.并且δ(¹⁷OH₂)与-E’IR对盐类浓度的变化率的大小满足如下顺序:KCl22.基于二态模型,可以证明伴随盐类浓度的改变,液态水化学位移的变化量△δ与其摩尔内能的变化量△E满足线性关系.以上结果表明,KCl、MgCl₂与CaCl₂对水分子的构造化具有促进作用,在对水分子缔合构造的表征上,液态水的内能变化与¹⁷O-NMR化学位移具有等效性.     

金纳米颗粒周围水的结构和动力学性质的分子动力学模拟

采用经典的分子动力学模拟方法系统地研究了在常温条件下金纳米颗粒周围水的结构与动力学性质. 结果表明, 水分子在纳米颗粒附近形成了明显的多层结构. 同时随着径向距离的减小, 水分子的空间取向也从无序排列趋向于有序排列. 通过分析界面处不同水层中的均方位移及停留时间分布, 发现紧贴颗粒表面的第一和第二水层中的水分子表现出很低的扩散系数, 而第三和第四水层中的水分子则能够轻易地离开界面区域而进入主体相区域. 此外, 在界面处的每个水分子的氢键平均数要高于在主体相的平均值.     

基于均苯三甲酸与对羟基吡啶的超分子水凝胶

以均苯三甲酸和对羟基吡啶为原料, 采用简便方法合成了一种新的凝胶因子, 并采用1H NMR、IR和元素分析确认其结构. 红外光谱中2849和1894 cm－1处出峰证明羧基与吡啶基间形成了氢键. 在凝胶化过程中, 凝胶因子可自组装形成纤维状网络结构. 随着凝胶因子浓度的增加, 纤维搭接逐渐致密, 凝胶网络密度逐渐增大, 可冻结水含量逐渐增加. 因此, 通过改变凝胶因子浓度可有效控制凝胶的结构及性能. 该凝胶因子在较低浓度下形成的超分子水凝胶在100 ℃下也能够稳定存在.     

Quantum Effects on Global Structure of Liquid Water

The structure difference between light and heavy liquid water has been systematically in-vestigated by high precision Raman spectroscopy over the temperature range of 5-85 oC. Distinct difference between the Raman spectral profiles of two different liquid waters is clearly observed. By analyzing the temperature-dependent Raman spectral contour using global fitting procedure, it is found that the micro-structure of heavy water is more ordered than that of light water at the same temperature, and the structure difference between the light and heavy water decreases with the increase of the temperature. The temperature off-set, an indicator for the structure difference, is determined to vary from 28 oC to 18 oC for the low-to-high temperature. It indicates that quantum effect is significantly not only at low temperature, but also at room temperature. The interaction energy among water moleculeshas also been estimated from van't Hoff's relationship. The detailed structural information should help to develop reliable force fields for molecular modeling of liquid water.     

低能氮离子与水的化学合成作用

化学改性是离子与物质相互作用的一种重要效应，即外来离子的介入引起材料中元素或基团间化学反应，更突出的是离子直接参与化合形成新的物质，从而改变材料的性质＊’1．近年来离子注入生物体产生独特的诱变效应引起了广泛关注问．注入离子在生物材料中引起的化学合成较好地解     

温度对液态水结构的影响：中子及X射线散射研究

采用中子散射和X射线散射研究了液态水在298～373 K温度范围内的结构,通过偏径向分布函数(PDF)、配位数分布(CN)、角分布(ADF)及空间密度分布(SDF)等讨论了温度对液态水结构的影响。整体来看,液态水具有"不规则四面体"氢键网络的短程有序结构,该有序度可延续到第三水合层。液态水分子的第一水合层中,围绕中心水分子约有4.8个水分子,然而其中仅有约3.3个水分子与中心水分子通过氢键相键合,约1/3进入到第一水合层的水分子并未与中心水分子直接键合,也正是这些间隙水分子的存在加剧了液态水结构的复杂性。温度对液态水的有序度存在一定的影响,在298～373 K的有限温度变化范围内,温度对液态水中氢键的键长、键角分布及第一水合层SDF的影响不大。从298K升温到373K,O(W)-O(W)距离仅增加0.03?,氢键数目也仅有微小减少,温度对第二和第三水合层的影响则要显著很多。     

Effects of Counter Ions in Ion-Pair Liquid Chromatography of Hydrophobic Amines on Non-Polar Bonded Phases

Abstract

The retention behaviour of alprenolol and related hydrophobic amines in ion-pair adsorption systems has been examined with particular emphasis on the influence of different mono-and divalent counter ions (dihydrogenphosphate, bromide, perchlorate, dimethylcyclohexyl sulphate, sulphate and ethylenediaminetetraacetate). N,N-dimethyloctylamine (DMOA) and 1-pentanol were used as modifiers in the aqueous eluent and LiChrosorb RP-8 as stationary phase.

The retention is evaluated according to a two-site adsorption model and equilibrium constants are given for ion pair adsorption of DMOA. The retention of alprenolol has been evaluated in terms of ion exchange with DMOA and the ion-exchange constants are shown to be of the same magnitude and independent of the nature of the counter ion used. The ion-pair adsorption and the ion-exchange approaches are analogous expressions for the distribution process governing the retention.     

不同电解质体系水的拉曼谱的研究

通过一系列电解质体系水的拉曼光谱测量，得到了阴、阳离子种类和浓度引起的水伸缩振动和弯曲振动谱带丰富的变化信息，ＣｌＯ４＾－能有效地破坏水分子间的氢键，随着ＣｌＯ４浓度的增加，水分子间的氢键并非逐步被打断，而是氢键被破坏的水分子越来越多，从而使水分子有序度增大，这种氢键破坏方式符合水的混合模型（ＭｉｘｔｕｒｅＭｏｄｅｌ）ＳＯ＾２－４浓度的增对水的Ｒａｍａｎ光谱影响较小，是由于ＳＯ＾２－４与水分了间的     

Effects of Ions on the OH Stretching Band of Water as Revealed by ATR-IR Spectroscopy

The effects of various cations (Li⁺, Na⁺, K⁺, Rb⁺, Cs⁺, Mg²⁺, Ca²⁺, Sr²⁺, Ba²⁺, Mn²⁺, Co²⁺, and Ni²⁺) and anions (Cl^?, Br^?, I^?, \( {\text{NO}}_{3}^{ - } \) , \( {\text{ClO}}_{4}^{ - } \) , \( {\text{HCO}}_{3}^{ - } \) , and \( {\text{CO}}_{3}^{2 - } \) ) on the molar absorptivity of water in the OH stretching band region (2,600–3,800 cm^?1) were ascertained from attenuated total reflection infrared spectra of aqueous electrolyte solutions (22 in all). The OH stretching band mainly changes linearly with ion concentrations up to 2 mol·L^?1, but several specific combinations of cations and anions (Cs₂SO₄, Li₂SO₄, and MgSO₄) present different trends. That deviation is attributed to ion pair formation and cooperativity in ion hydration, which indicates that the extent of the ion–water interaction reflected by the OH stretching band of water is beyond the first solvation shell of water molecules directly surrounding the ion. The obtained dataset was then correlated with several quantitative parameters representing structural and dynamic properties of water molecules around ions: ΔG _HB, the structural entropy (S _str), the viscosity B-coefficient (B _η ), and the ionic B-coefficient of NMR relaxation (B _NMR). Results show that modification of the OH stretching band of water caused by ions has quasi-linear relations with all of these parameters. Vibrational spectroscopy can be a useful means for evaluating ion–water interaction in aqueous solutions.     

Effects of the Liquid Conductivity on Pulsed High-voltage Discharge Modes in Water

Spark, stream and corona pulsed high-voltage discharges in water induced by the various initial conductivities have been examined in this paper. The discharge modes changed from spark to corona discharge with the liquid conductivity increasing. The apparent production of OH radical and quantum yield generated by spark discharge in distilled water were 11.57 gmol/L and 0.0978 photon/s, respectively. A preliminary study on acid fuchsine (AF) treatment indicated that higher AF removal efficiency has been achieved by spark discharge. The process of degradation showed that the oxidative effects through OH radical oxidation did not play an important role and did increase with the discharge mode changing to spark discharge.     

Tetraalkylammonium Picrates in the Dichloromethane–Water System: Ion-Pair Formation and Liquid–Liquid Distribution of Free Ions and Ion Pairs

Equilibria concerning picrates of tetraalkylammonium ions (Me₄N⁺, Et₄N⁺, Pr₄N⁺, Bu₄N⁺, Bu₃MeN⁺) in a dichloromethane−water system have been investigated at 25 ^∘C. The 1:1 ion-pair formation constants (K _IP,o ^o) in dichloromethane at infinite dilution were conductometrically determined. The distribution constants (K _D ^o) of the ion pairs and the free cations between the solvents were determined by a batch-extraction method. The K _IP,o ^o value varies in the cation sequence, Bu₄N⁺ ≈ Pr₄N⁺ ≈ Et₄N⁺ < Bu₃MeN⁺ < < Me₄N⁺; this trend is explained by the electrostatic cation−anion interaction taking into account the structures of the ion pairs determined by density functional theory calculations. For the ion pairs of the symmetric R₄N⁺ cations, there is a linear positive relationship between log₁₀ K _D ^o and the number of methylene groups in the cation (N _{CH 2}). The ion pair of asymmetric Bu₃MeN⁺ has a higher distribution constant than that expected from the above log₁₀ K _D ^o versus N _{CH 2} relationship. These cation dependencies of log₁₀ K _D ^o for the ion pairs are explained theoretically by using the Hildebrand-Scatchard equation. For all the cations, the log₁₀ K _D ^o value of the free cation increases linearly with N _{CH 2}; the variation of log₁₀ K _D ^o is discussed by decomposing the distribution constant into the Born-type electrostatic contribution and the non-Born one, and attributed to the latter that is governed by the differences in the molar volumes of the cations. The cation dependencies of the ion-pair extractability and ion pairing in water are also discussed. An erratum to this article can be found at