<Superscript>1</Superscript>H MAS NMR spectra of kaolinite/formamide intercalation compound

The high spinning speed ¹H magic angle spinning nuclear magnetic resonance (¹H MAS NMR) technique was employed to distinguish the two groups of surface hydroxyls of kaolinite and investigate the intercalation mechanism of kaolinite/formamide compound. The proton chemical shifts of the inner hydroxyl and inner surface hydroxyl of kaolinte are in the range of δ−1.3–−0.9 and δ 2.4–3.0 respectively. After formamide intercalation three proton peaks were detected. The proton peak of the inner surface hydroxyls of the intercalation compound shifts to high-field with δ 2.3–2.7, which is assigned to the formation of the hydrogen bond between the inner surface hydroxyl and formamide carbonyl group. Whereas, the proton peak of the inner hydroxyl shifts to δ −0.3 toward low-field, that is attributed to van der Waal’s effect between the inner hydroxyl proton and the amino group proton of the formamide which may be keyed into the ditrigonal hole of the kaolinite. The third peak, additional proton peak, is in the range of δ5.4–5.6, that is ascribed to the hydrogen bond formation between the amino group proton of formimide and SiO₄ tetrahedral oxygen of the kaolinite.     

1H MAS NMR spectra of hydroxyl species on diatomite surface

High spinning speed¹H magic-angle spinning nuclear magnetic resonance (¹H MAS NMR) was used to detect surface hydroxyl groups of diatomite, which include isolated hydroxyl groups and hydrogen-bonded hydroxyl groups, and water adsorbed on diatomite surface that include pore water and hydrogen-bonded water. The corresponding proton chemical shifts of above species are ca. 2.0, 6.0–7.1, 4.9 and 3.0 respectively. Accompanied by thermal treatment temperature ascending, the pore water and hydrogen-bonded water are desorbed successively. As a result, the relative intensities of the peaks assigned to protons of isolated hydroxyl groups and hydrogen-bonded hydroxyl groups increase gradually and reach their maxima at 1000°C. After 1100°C calcination, the hydroxyl groups that classified to strongly hydrogen-bonded ones and the isolated hydroxyl groups condense basically. But some weakly hydrogen-bonded hydroxyl groups may still persist in the micropores.     

两种黏土矿物催化木质素腐殖化过程机理

利用扫描电子显微镜（SEM）、 Fourier变换红外光谱（FTIR）和X射线衍射（XRD）研究高岭石和蒙脱石参与木质素接种混合菌株悬液液体摇瓶培养110 d的结构特征变化. 结果表明： 高岭石参与木质素微生物转化后, 结构水失衡, 边缘断键使其表面集聚负电荷, 表面水化层多点形成氢键, 增加了缔合—OH的伸缩振动, Al—OH的边缘及基底八面体O均发生脱羟作用, 使四面体片和八面体片变形并产生大量断键, 导致Si—O,Si—O—Al及Si—O—Si[KG*8]振动频率弱化, 晶体结构向长程无序转变, 但未发生物相改变; 蒙脱石为膨胀性矿物, 内部亲水, 经液体摇瓶培养后, 结晶水收缩使层间结构被破坏, 增加了表面粗糙程度, 参与木质素微生物转化后, 微生物释放的胞外聚合物与蒙脱石表面官能团形成氢键, 使羟基总量及层间和晶格中的结晶水降低, 并提高了Si—O,Mg—Al—OH和Fe—O—Si键（或Mg—O—Si键）的振动频率, 低波处的特征衍射峰消失.     

水环境下氢氧根水分子簇催化缬氨酸旋光异构及羟自由基致其损伤机理

基于MP2/6-311++G(2df,pd)//B3LYP/6-31+G(d,p)双理论水平, 用自洽反应场(SCRF)理论的SMD模型方法, 考察水环境下氢氧根水分子簇催化缬氨酸旋光异构及羟自由基致其损伤机理. 结果表明： 缬氨酸的旋光异构可在2个通道a和b实现, 通道a为氢氧根水分子簇与α-H和氨基通过氢键作用形成底物, 氢氧根抽取α-H后, α-C在另一侧抽取水分子的H; 通道b为氢氧根水分子簇与α-H和羰基通过氢键作用形成底物, 氢氧根抽取α-H后, α-C在另一侧抽取水分子的H, 通道b中的水分子辅助羟自由基抽取α-H可致缬氨酸损伤; 水液相环境下, 构象Val-1（氨基羧基间为单氢键）和构象Val-2（氨基羧基间为双氢键）在通道a旋光异构的决速步骤能垒分别为60.57,65.24 kJ/mol, 在通道b旋光异构的决速步骤能垒分别为56.76,64.11 kJ/mol, 羟自由基水分子簇致缬氨酸在通道b的损伤为温和的放热反应.     

高岭石层间尿素-水体系的分子动力学模拟

用分子动力学（MD）方法对尿素-高岭石和尿素-水-高岭石两个体系进行模拟,计算结果表明,在300K时,高岭石平衡层间距随着尿素分子的增多不断增大,增幅逐渐减小;尿素在水溶液中的摩尔分率在0.58左右时高岭石平衡层间距有最大值。尿素在高岭石片层间成双层分布,分别通过O=C键和N—H键与高岭石表面原子形成氢键。水在层间主体相成三层分布,有部分水分子吸附在高岭石表面上。     

几种黄酮类化合物核磁共振谱的理论研究

在B3LYP／6—31G水平下优化了3种黄酮类化合物的几何构型．在振动分析中，均未出现虚频率．在B3LYP／6—31G的水平下采用了GIAO方法计算了该类化合物的核磁共振碳谱．研究结果表明：3种分子均有分子内氢键形成，且分子内氢键的键长为0．17nm左右．讨论了羟基引入之后对邻近C的化学位移的影响．从取代基对NMR的影响来看，随着取代基对苯环的供电子能力的加强，取代基邻近的一些C的化学位移有所改变．     

1-羟基-2-萘甲醛分子基态和激发态的质子转移机制

基于密度泛函与含时密度泛函理论方法,研究1-羟基-2-萘甲醛(HN12)分子及分子异构体在基态和激发态的氢键动力学过程.结果表明:在基态的HN12分子被激发至第一电子激发态后,出现氢键键长变短及氢键中羟基的红外光谱红移现象;激发态分子内的质子可发生转移反应;异构体在激发态时不易发生逆向的质子转移反应,但在基态较易出现逆向的质子转移过程.即HN12分子及分子异构体在基态和激发态存在一个循环机制.     

Crystal structure of an RNA double helix incorporating a track of non-Watson-Crick base pairs

The crystal structure of the RNA dodecamer duplex (r-GGACUUCGGUCC)2 has been determined. The dodecamers stack end-to-end in the crystal, simulating infinite A-form helices with only a break in the phosphodiester chain. These infinite helices are held together in the crystal by hydrogen bonding between ribose hydroxyl groups and a variety of donors and acceptors. The four noncomplementary nucleotides in the middle of the sequence did not form an internal loop, but rather a highly regular double-helix incorporating the non-Watson-Crick base pairs, G.U and U.C. This is the first direct observation of a U.C (or T.C) base pair in a crystal structure. The U.C pairs each form only a single base-base hydrogen bond, but are stabilized by a water molecule which bridges between the ring nitrogens and by four waters in the major groove which link the bases and phosphates. The lack of distortion introduced in the double helix by the U.C mismatch may explain its low efficiency of repair in DNA. The G.U wobble pair is also stabilized by a minor-groove water which bridges between the unpaired guanine amino and the ribose hydroxyl of the uracil. This structure emphasizes the importance of specific hydrogen bonding between not only the nucleotide bases, but also the ribose hydroxyls, phosphate oxygens and tightly bound waters in stabilization of the intramolecular and intermolecular structures of double helical RNA.     

系列小分子与碱基尿嘧啶间氢键相互作用的理论研究

核酸碱基尿嘧啶分子可以使用3个不同位点与其他分子形成多种类型的分子间氢键.笔者使用密度泛函理论B3LYP/6-31＋G（d,p）方法优化得到了系列小分子与尿嘧啶分子形成的31个氢键复合物的稳定结构,进而使用MP2/aug-cc-pVTZ方法计算了这些氢键复合物的结合能.研究结果表明,尿嘧啶分子更倾向作为氢键给体与小分子形成氢键.尿嘧啶分子最易使用1号位点与小分子形成氢键复合物,最不易使用2号位点形成氢键复合物.甲基取代小分子氢键受体上的氢原子会使氢键强度变强.为了深入理解这些氢键复合物体系中氢键作用的本质,还使用B3LYP/6-31G（d,p）方法进行了自然键轨道（NBO）分析计算.自然键轨道（NBO）分析表明,大部分氢键复合物满足二阶相互作用稳定化能之和越大,结合能绝对值越大,结合得越稳定的原则,说明共价作用在这些氢键作用中起重要作用.     

Interaction of Divalent Metal Ions with the Adenosine Triphosphate Measured Using Nuclear Magnetic Resonance

Theinteractionofadenosinetriphosphatewithdivalentmetalionsisimportantinbiochemicalfunctions.TheintracellularfreeMg2 canbeestimated[1]byseparatingtheα-andβ-phosphatepeaksoftheATPNMR31PspectrumandbyknowingtheMgATPdissociationconstant.TheneedfordivalentmetalionsforallenzymaticreactionsinvolvingATPiswellknown,buttheroleofthemetalionsisnotclear[2].ThisstudywasconductedtoobtaininformationconcerningchangesinthestructureofadenosinetriphosphatecausedbyinteractionwithdivalentmetalionsMg2 ,Ca2 ,…     

Surface modification of γ-Al2O3 by sodium ions

¹H/²³Na double resonance NMR techniques were employed to study the modification of surface hydroxyls on γ-Al₂O₃ by sodium ions. ¹H→²³Na cross polarization (CP) experiment can resolve three kinds of sodium cations that are closely associated with surface hydroxyl groups, while the signal of deposited salt-Na₂CO₃, which is not connected to surface hydroxyl groups, is completely suppressed. ¹H{²³Na} spin echo double resonance experiments reveal the surface modification in more detail. At low Na⁺ coverage (5%, 10%), the acidic hydroxyl groups are preferentially coordinated with sodium ions, while both the acidic and the basic hydroxyl groups are accessible for sodium ions at high coordination that causes proton of the OH groups to be easily dissolved, which is evidenced by the fact that with calcination temperature of the catalysts increasing, the acidic hydroxyl groups are preferentially removed and only the basic hydroxyl groups remain when the calcination temperature is raised to 600℃.     

一种用于阳图CTP版材的改性酚醛树脂的合成

以双酚A-甲醛树脂和N,N_二甲基甲酰胺在三氯氧磷的催化作用下发生酯化反应,将酯化产物与乙烯基乙基醚在溶剂存在条件下发生醚化反应,得到双酚A-甲醛树脂的酯醚化合物,经红外光谱确认其已被酯醚化.对产物的红外吸收谱进行研究,该树脂的羟基因被酯醚化其吸收明显减少,在有酸条件下促溶无酸时阻溶,将其应用于热敏阳图CTP版材,证明版材敏度得到提高.     

甘油溶液声速、核磁共振信号峰面积变化规律的微观机理研究

利用超声光栅法和核磁共振法测量了不同浓度甘油溶液的声速和核磁共振信号峰面积,对其实验原理和实验现象进行了解释,将声速与氢键含量、核磁共振信号峰面积与能级跃迁相联系。结果表明：随着甘油溶液浓度的升高,声速快慢与氢键含量具有相似的变化规律,信号峰面积则与氢核数目变化规律相类似。     

金纳米粒子在聚合物微球上的自组装

本文在不添加任何稳定剂的情况下利用蒸馏沉淀聚合法,合成了表面带有大量活性羟基的聚合物微球。所得到的微球通过丙烯酰氯酯化其表面的羟基引入碳碳双键,然后在pH=10-11的条件下在双键加成硫化氢从而成功制备了单分散的表面带疏基的聚合物微球。利用疏基和Au之间强的相互作用,将金纳米粒子自组装与微球表面。     

基于氨基作为质子转移桥梁的赖氨酸分子手性转变机理

采用密度泛函理论的B3LYP方法和微扰理论的MP2方法, 考察赖氨酸分子基于氨基作为质子转移桥梁的手性转变机理以及水分子和羟基自由基对氢迁移反应的催化作用. 结果表明, 赖氨酸分子手性转变有2个通道a和b, 通道a为主反应通道, 决速步骤裸反应Gibbs自由能垒为252.6 kJ/mol, 2个水分子构成的链以及羟基自由基和水分子构成的链使通道a决速步骤的自由能垒分别降为119.5,98.5 kJ/mol. 表明水分子和羟自由基对H迁移反应有较好的催化作用, 生命体内的羟基自由基是导致左旋赖氨酸旋光异构的主要原因.     

淀粉分子电子结构的量子化学研究(Ⅰ):结构单元、糖苷键和氢键的特性

运用量子化学计算研究淀粉分子的微观结构和化学键的性质，淀粉分子的反应活性中心为C3位，C2位和C6位羟基，活性顺序为C3位羟基＞C2位羟基＞C6位羟基。糖苷键的成键效应不大，反键效应较明显，糖苷键中C－O键极性大，键级小，氧上带很多电荷。离子性明显，易受亲电试剂（如氢离子）的进攻。     

生命科学中的微催化作用研究──人参皂甙的提取和人参二醇的量子化学计算

生命科学中的微催化作用研究人参皂甙的提取和人参二醇的量子化学计算①廖代伟陆健年林银钟何苏雄黄遵楠（厦门大学物理化学研究所化学系厦门３６１００５）要在原子或分子水平上深入了解催化作用，除了传统的着眼于宏观的工业催化剂和工业催化过程的研制开发外，应更重视...     

苯丙氨酸分子的手性对映体转变机理及水分子（簇）的催化作用

在MP2/6 311++G(3-df,2pd-)//WB97X-D/6-311++G(-d,p-)双水平研究苯丙氨酸(Phe)分子的手性对映体转变机理, 并用分子中的原子理论(AIM)分析驻点的成键特征. 结果表明： 经过羧羟基旋转、 质子迁移、 碳 碳键旋转和氨基翻转的一系列过渡态, Phe分子在质子以氨基氮为桥梁迁移的通道a和以羰基氧与氨基氮顺次为桥梁迁移的通道b内, 实现了手性对映体转变; 当2个水分子簇作为质子迁移媒介时, 在通道b中增加了质子仅以羰基氧为桥梁迁移的反应路径； 通道a具有优势, 速控步骤的内禀能垒为25971 kJ/mol, 反应的表观能垒为27026 kJ/mol； 2个水分子簇催化使速控步骤的内禀能垒降至126.47 kJ/mol, 反应的表观能垒降至80.80 kJ/mol; 考虑零点振动能后, 质子从氨基氮向羰基氧迁移的能垒消失. 即水分子（簇）催化可使Phe分子实现手性对映体转变.     

叶酸受体在血液肿瘤细胞株的表达及叶酸-聚乙烯亚胺共聚物的制备

目的:研究叶酸受体(folate receptor,FR)在血液肿瘤细胞表达的特点,合成叶酸-聚乙烯亚胺(FA-PEI)聚合物,探讨其作为靶向性基因输送载体的可行性.方法:用实时荧光定量PCR(real time PCR)法检测α、β、γ3种FR在血液肿瘤细胞K562、K562/A02、U266细胞株上的表达;利用叶酸(FA)活性酯在微碱性条件下与聚乙烯亚胺(polyethylenimine,PEI)的支链氨基反应,合成FA-PEI共聚物;用葡聚糖凝胶柱G-25分离、纯化;用紫外分光光度计波长扫描法及氢核磁共振谱(~1H NMR)法验证交联是否成功.结果:α、β、γ3种FR在K562、K562/A02、U266 3种细胞株上均表达,其中,α-FR的表达占优势,较β-FR和γ-FR表达量高;紫外分光光度计扫描图谱在365 nm处出现叶酸的特征性吸收峰;核磁共振(~1H NMR)示:在2.5～3.2处出现PEI亚甲基质子的特征性化学位移,在6.5～9.0处出现叶酸芳香质子的特征性氢信号.结论:FR在K562、K562/A02、U266 3种细胞株上均有较高表达;FA-PEI偶联成功,为其作为血液肿瘤治疗中1种潜在的靶向性基因输送载体提供了依据.     

水液相环境下赖氨酸旋光异构及羟自由基致其损伤的机理

在MP2/6-311++G(2-df,pd-)//B3LYP/6-31+G(d,p)双理论下, 采用自洽反应场(SCRF)理论的SMD模型方法, 研究水液相环境下, 两种稳定构象赖氨酸分子基于氨基氮为氢迁移桥梁的旋光异构过程及羟自由基致其损伤的机理. 势能面计算结果表明： 在水液相环境下, 当2个和3个水分子簇作为氢迁移媒介时, 构象1旋光异构的决速步骤Gibbs自由能垒分别为116.02,112.71 kJ/mol, 构象2旋光异构的决速步骤Gibbs自由能垒分别为110.27,114.29 kJ/mol; 当羟自由基与水分子链作为氢迁移媒介时, 羟自由基抽氢致赖氨酸分子构象1和构象2损伤的Gibbs自由能垒分别为-53.06,-56.05 kJ/mol, 均为无势垒反应. 即在水液相环境下, 赖氨酸分子可缓慢地旋光异构, 羟自由基可迅速致赖氨酸损伤.