PNIPA和PDEA在水-甲醇混合溶剂中性质的研究

分别研究了聚N-异丙基丙烯酰胺（PNIPA）和聚N,N-二乙基丙烯酰胺（PDEA）在水-甲醇混合溶剂中的溶液性质.结果表明,在PDEA和PNIPA体系中均存在水和甲醇分子之间的复合.由于PDEA比PNIPA的亲脂性强,在水-甲醇混合溶剂中,水与甲醇分子形成的复合物对PDEA和PNIPA的溶剂化作用不同,导致随着体系中甲醇体积分数（φ）的增大,PNIPA体系的低临界溶解温度（TLCS）发生了再进入相转变,而PDEA体系的TLCS则逐渐升高.     

反相液相色谱中溶质保留与溶剂化结构参数间的定量关系

本文研究了等度条件下反相液相色谱中溶质保留与溶剂化结构参数间的定量关系;考察了反相液相色谱保留值变化规律式lnk'=a+cC~b中参数a.c 与溶剂化结构参数间的定量关系,结果表明能较好地预测等度和不同冲洗剂组成下溶质的保留值,将乙腈-水和甲醇-水冲洗剂下的a.c值定量关联,表明在考虑溶质的氢键作用参数后,其相关性有所提高.     

反相液相色谱中溶质保留与溶剂化结构参数间的定量关系

本文研究了等度条件下反相液相色谱中溶质保留与溶剂化结构参数间的定量关系;考察了反相液相色谱保留值变化规律式lnk'=a+cC~b中参数a.c 与溶剂化结构参数间的定量关系,结果表明能较好地预测等度和不同冲洗剂组成下溶质的保留值,将乙腈-水和甲醇-水冲洗剂下的a.c值定量关联,表明在考虑溶质的氢键作用参数后,其相关性有所提高.     

NTO二聚体分子间相互作用的理论研究

在DFT-B3LYP/6-311＋＋G**水平上求得NTO二聚体势能面上六种优化构型和电子结构. 经基组叠加误差(BSSE)和零点能(ZPE)校正, 求得分子间最大相互作用能为－53.66 kJ/mol. 二子体系间的电荷转移很少. 由自然键轨道分析揭示了相互作用的本质. 对优化构型进行振动分析, 并基于统计热力学求得200.0～800.0 K温度范围从单体形成二聚体的热力学性质变化. 发现二聚主要由强氢键所贡献, 但结合能大小并不为氢键所完全决定. 二聚过程在较低温度或常温下能自发进行.     

具多重氢键寡聚芳酰胺的合成及自组装

含六重氢键寡聚芳酰胺双分子链在没有相应互补链的情况下, 其中一条链发生自组装. 通过紫外-可见(UV-Vis)光谱、动态光散射(DLS)、扫描电镜(SEM)和透射电镜(TEM)等实验手段, 对其自组装行为进行了研究. 实验结果表明, 在1,2-二氯乙烷中随温度升高在紫外区吸收发生蓝移, 说明酰胺自组装体部分解聚. 该分子链在不同极性的溶剂中都能发生自组装, 并随极性不同表现为不同的形貌. 如在甲苯中呈网状结构, 在极性相对较弱的二氯甲烷和环己烷的混合溶剂中为不规则的蜂窝状结构, 而在三氯甲烷和甲醇组成的极性混合溶剂中则组装成稳定的实心微球, 其直径随着浓度升高而增大, 通过在乙腈中的降温过程, 观察到组装体形貌由管状纤维向实心球的转变.     

胰岛素六聚体在水溶液中的稳定性研究

用分子动力学（MD）模拟方法设计了两个模拟时间为600ps的对比计算机模拟 实验,研究了R6态的胰岛素六聚体在水溶液中的稳定性以及苯酚和锌离子对结构稳 定性的影响。通过对MD模拟所得到的轨迹的分析发现,在维系胰岛素六聚体稳定性 的因素中,静电相互作用和氢键起着主要的作用。对于包含锌离子和苯酚的体系。 胰岛素六聚体的稳定性得到了增强;对不含锌离子和苯酚的关系,胰岛素六聚体的 稳定性明显减弱,在这种情况下,胰岛素六聚体还表现出解聚的倾向。这些模拟结 果与实验观测结果相吻合。     

二元组装体集群时的高选择性杂化重组行为

多样性自组装体在混合时,通常表现出互不干扰的自分类性,能高度选择性地自分类堆积.但结构极为相似的组装子在相互混合时,会发生交互作用并表现出重组现象.文中合成和观测了具有芳香环边墙和不同酰胺侧链的C型甘脲分子夹为组装单元的混合组装行为.研究发现,此类分子在各自以单一态物质溶解于CDCl3时,能通过π-π相互作用和氢键形成二聚自组装体;若将两种具有不同酰胺侧链的C型甘脲分子夹两两混合,从理论上推测应有三种二聚自组装堆积态存在：A·A、B·B、A·B.但经1HNMR分析发现了一个有趣的现象,即当酰胺侧链上的取代基R′分别为具有C-H结构（如1和2）与PhF5基（5）的组装体两两混合时,二聚组装主要呈现出高度选择性杂化重组的A·B结构态.这种取代基控制的高选择性重组行为可能是基于π-π相互作用、N—H…O氢键,以及C—H…π等三重作用力的协同结果.     

甲醇协助丙交酯开环聚合反应的理论研究

采用密度泛函理论在B3LYP/6-31G(d,p)水平上研究了甲醇协助的丙交酯开环聚合反应, 探讨了1~3个甲醇分子参与的丙交酯聚合反应机理, 考察了溶剂化效应对聚合反应的影响. 结果表明, 甲醇协助的丙交酯开环聚合按加成-消除机理进行; 甲醇分子作为质子给体与受体通过与丙交酯形成环状氢键促进开环聚合, 随着甲醇分子数的增加, 环状氢键的张力逐渐减小, 反应能垒随之降低; 溶剂化效应对反应机理和反应势垒的影响均可忽略不计.     

MgCl2/甲醇溶液的近红外光谱研究及量子计算

利用近红外光谱研究了MgCl2/甲醇溶液中的氢键种类及其变化和溶液离子化作用. 近红外光谱结果分析表明, Mg2＋与溶剂发生了强烈的相互作用导致溶液中的氢键发生变化. 随着MgCl2浓度的增加, 多聚体氢键(δ-OHs)减少, 低聚体和二聚体氢键(γ-OHs)增加, OHs总数维持不变. 通过对光谱曲线的分解拟合, 定量地计算了不同浓度范围(0.21～0.62 mol•kg－1)内Mg2＋的溶剂化数为5.5到5.0. 并利用量子化学方法对溶剂化数为5和6的配合物结构进行优化及热力学性质的计算, 通过光谱变化及理论计算推断Cl－可能会以氢键结合甲醇分子的形式存在.     

2-氨基苯并噻唑的结构及激发态质子转移动力学

通过傅里叶变换红外光谱（FTIR）、傅里叶变换拉曼（FT-Raman）和488 nm拉曼光谱,结合密度泛函理论（DFT）计算研究了2-氨基苯并噻唑（ABT）在晶态和溶剂中的二聚体结构,并解释了质子性溶剂中ABT二聚体与溶剂分子间的氢键作用.电子光谱实验揭示了ABT二聚体的光物理和光化学反应;紫外吸收和荧光发射光谱结果表明,溶剂、激发波长和pH值对ABT二聚件激发态衰变具有调控作用;含时密度泛函理论（TD-DFT）解释了ABT二聚体双荧光现象,提出了高激发态的质子转移机理.     

DFT Calculation of Glycine with Methanols Clusters

Density functional theory （DFT） calculations are reported for the structures of neutral and zwitterionic glycine-（CHaOH）n where n=1-6. Initial geometries of the clusters of neutral and zwitterionic glycine with 1-6 methanol molecules are fully optimized at B3LYP/6-31＋G^＊ level of theory. The lowest energy configurations are located and their hydrogen bond structures are analyzed. Theoretical prediction reveals that the methanols prefer to locate near the carboxylic acid group for the small clusters （n_〈3） with the neutral form while the configurations with the methanols bridging the acid and the amino group are favorite in the zwitterionic form clusters. When the number of the methanol molecules in the clusters reaches five and six, the two forms tend to be isoenergetic.     

HOCl…HCOCl复合物的结构和电子性质

在DFT-B3LYP/6-311++G**水平上求得HOCl+HCOCl复合物势能面上的四种稳定构型(S1,S2,S3和S4).其中,在复合物S1和S3中,HOCl单体的5H原子作为质子供体,与HCOCl单体中作为质子受体的10原子相互作用,形成红移氢键复合物;在复合物S4中,HOCl单体的7Cl原子作为质子供体,与HCOCl单体中作为质子受体的IO原子相互作用,形成红移卤键复合物;而在复合物S2中,同时存在2C-3H…6O蓝移氢键和4Cl…5O相互作用.在MP2/6-311++G**水平上计算的单体间的相互作用能考虑了基组重叠误差(BSSE)和零点振动能(ZPVE)校正,其值在-5.05与-14.76 kJ·mol-1之间.采用自然键轨道理论(NBO)对两种单体间相互作用的本质进行了考查,并通过分子中原子理论(AIM)分析了复合物中氢键和卤键键鞍点处的电子密度拓扑性质.     

Theoretical Study on Hydrogen Interaction between 5-Fluorouracil and Glycine

The geometries,electronic structure,IR spectrum and other properties of hydrogen interaction between 5-fluorouracil and glycine were studied at the B3LYP/6-31+G* level.Single point energy calculations were executed at the B3LYP/6-311++G** and B3LYP/aug-cc-pvdz levels,and natural bond orbital (NBO) analysis was carried out at the B3LYP/6-31+G* level.Finally,the hydrogen bonds were discussed via AIM electronic density topology analysis.     

Semiempirical PM5 molecular orbital study on chlorophylls and bacteriochlorophylls: comparison of semiempirical, ab initio, and density functional results

The semiempirical PM5 method has been used to calculate fully optimized structures of magnesium-bacteriochlorin, magnesium-chlorin, magnesium-porphin, mesochlorophyll a, chlorophylls a, b, c(1), c(2), c(3), and d, and bacteriochlorophylls a, b, c, d, e, f, g, and h with all homologous structures. Hartree-Fock/6-31G* ab initio and density functional B3LYP/6-31G* methods were used to optimize structures of methyl chlorophyllide a, chlorophyll c(1), and methyl bacteriochlorophyllides a and c for comparison. Spectroscopic transition energies of the chromophores and their 1:1 or 1:2 solvent complexes were calculated with the Zindo/S CIS method. The self-consistent reaction field model was used to estimate solvent shifts. The PM5 calculations predict planar structure of the porphyrin ring and central position of the four coordinated magnesium atoms in all pigments studied, in accord with the experimental, ab initio, and density functional results, a significant improvement as compared to the older semiempirical PM3 approach. Only small differences in PM5 and B3LYP/6-31G* or Hartree-Fock/6-31G* minimum energy geometries of the reference molecules were observed. Calculations show that in 1:1 solvent complexes, where the magnesium atom is five coordinated, the magnesium atom is shifted out of the plane of the porphyrin ring towards the solvent molecule, while the hexa coordinated 1:2 complexes are again planar. The PM5 method gives atomic charges that are comparable with those obtained from the Hartree-Fock/6-31G* and B3LYP/6-31G* calculations. The single point ZINDO/S CIS calculations with PM5 minimum energy structure gave excellent correlations between calculated and experimental transition energies of the chlorophylls and bacteriochlorophylls studied. Such correlations may be used for prediction of transition energies of the chromophores in protein binding sites. Calculations also predict existence of dark electronic states below the main Soret absorption band in all chromophores studied. The results suggest that the semiempirical PM5 method is a fairly reliable and computationally efficient method in predicting molecular parameters of porphyrin-like molecules.     

多肽中氢键强度的理论研究

用B3LYP/6-31G^*法优化了多肽分子的几何构型,计算了各个构型的电荷分布和氢键酸度,进而对多肽分子中的氢键强度进行了研究.结果表明,多肽分子中氢键的强度同时取决于形成氢键的H…O原子间距R和N-H…O之间的键角β;多肽分子倾向于形成R值小、β值大的大环氢键.3₁₀螺旋结构的多肽分子中的氢键具有协同效应,分子越大,分子中氢键越多,氢键的协同效应越强.     

A simple model for metal cation-phosphate interactions in nucleic acids in the gas phase: Alkali metal cations and trimethyl phosphate

Threshold collision-induced dissociation techniques are employed to determine the bond dissociation energies (BDEs) of complexes of alkali metal cations to trimethyl phosphate, TMP. Endothermic loss of the intact TMP ligand is the only dissociation pathway observed for all complexes. Theoretical calculations at the B3LYP/6-31G* level of theory are used to determine the structures, vibrational frequencies, and rotational constants of neutral TMP and the M+(TMP) complexes. Theoretical BDEs are determined from single point energy calculations at the B3LYP/6-311+G(2d,2p) level using the B3LYP/6-31G* optimized geometries. The agreement between theory and experiment is reasonably good for all complexes except Li+(TMP). The absolute M+-(TMP) BDEs are found to decrease monotonically as the size of the alkali metal cation increases. No activated dissociation was observed for alkali metal cation binding to TMP. The binding of alkali metal cations to TMP is compared with that to acetone and methanol.     

水、甲醇和乙醇液体微结构性质的Car-Parrinello 分子动力学模拟

采用Car-Parrinello 分子动力学(CPMD)方法分别研究了水、甲醇和乙醇的液体微结构性质.研究结果显示:在水、甲醇和乙醇三个体系中O…O径向分布函数曲线的第一个峰位置分别为0.278、0.276 和0.275nm; O…H径向分布函数曲线的第一个峰位置分别为0.178、0.176和0.177 nm.表明基团(氢原子、甲基、乙基)的差异对O…O第一个峰的位置影响很小.但基团的差异对径向分布函数峰高的影响却很显著,由水到乙醇第一个峰的高度逐渐变高.空间分布函数表明氧原子和氢原子在溶剂分子周围有取向地分布,这与径向分布函数所表现出尖锐的第一个峰相一致.氢键分布分析显示,水、甲醇和乙醇的平均氢键数分别为3.62、1.99 和1.87,表明水形成了网状氢键结构,而甲醇、乙醇形成链状氢键结构.     

DFT Calculations on Hydrogen-Bonded Complexes Formed Between Guanine and Acrylamide

B3LYP/6-311+G* theoretical calculations have been employed to investigate the complexes involving hydrogen bonding between guanine and acrylamide. Nine stable conformers were obtained by geometry optimization without imaginary frequencies. The calculation results revealed that the stability of these complexes was accounted for by the intensity and numbers of hydrogen bonds between guanine and acrylamide, which was proved by the energy analysis and the topological properties at the critical points. In these optimized complexes, the complex with three hydrogen bonds was the most stable one because it offered the biggest binding energy. Clearly, the hydrogen bonds appear to be crucial in the stability of these complexes. This work will provide another nosogenetic interpretation besides the covalent interactions between DNA and acrylamide, which are of interest for studying DNA mutation.     

Study of hydrogen bonding interactions relevant to biomolecular structure and function

Ab initio molecular orbital calculations were used to study hydrogen bonding interactions and interatomic distances of a number of hydrogen bonded complexes that are germane to biomolecular structure and function. The calculations were carried out at the STO-3G, 3-21G, 6-31G*, and MP2/6-31G* levels (geometries were fully optimized at each level). For anionic species, 6-31 + G* and MP2/6-31 + G* were also used. In some cases, more sophisticated calculations were also carried out. Whenever possible, the corresponding enthalpy, entropy, and free energy of complexation were calculated. The agreement with the limited quantity of experimental data is good. For comparison, we also carried out semiempirical molecular orbital calculations. In general, AM1 and PM3 give lower interaction enthalpies than the best ab initio results. With regard to structural results, AM1 tends to favor bifurcated structures for O? H-O and N? HO types of hydrogen bonds, but not for hydrogen bonds involving O-H? S and S-H? O, where the usual hydrogen bond patterns are observed. Overall, AM1 geometries are in general in poor agreement with ab initio structural results. On the other hand, PM3 gives geometries similar to the ab initio ones. Hence, from the structural point of view PM3 does show some improvement over AM1. Finally, insights into the formation of cyclic or open formate–water hydrogen bonded complexes are presented. © 1992 by John Wiley & Sons, Inc.     

Density functional theory study of the hydrogen bonding interaction of 1:1 complexes of serine with water

The hydrogen bonding of 1:1 complexes formed between serine and water molecules were completely investigated in the present study employing ab initio and Density Functional Theory (DFT) methods at varied basis set levels from 6‐31g to 6‐311++g (2d,2p). For comparison, we also used the second‐order Moller–Plesset Perturbation (MP2) method at the 6‐31+g(d) level. Twelve reasonable geometries on the potential energy hypersurface of serine and water system were considered with the global minimum, 10 of which are cyclic double‐hydrogen bonded structures and the other two are one‐hydrogen bonded structures. The optimized geometric parameters and interaction energies for various isomers at different levels were estimated. The infrared spectrum frequencies, IR intensities, and the vibrational frequency shifts are reported. Finally, the solvent effects on the geometries of the serine–water complexes were also investigated using self‐consistent reaction‐field (SCRF) calculations at the B3LYP/6‐311++g(d,p) level. The results indicate that the polarity of the solvent played an important role in the structures and relative stabilities of different isomers. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005