蛋白质在疏水色谱中的变性热力学

研究21-80℃温度范围内一些蛋白质和小分子在疏水相互作用色谱中的热行为。利用Van't Hoff作图(lnk'-1/T)测定蛋白质分子的热力学参数(ΔH°, ΔS°和ΔG°), 根据标准熵变(ΔS°)和标准自由能变(ΔG°)判断蛋白质在色谱过程中的构象变化, 通过ΔH°-ΔS°的线性关系估计蛋白质变性时的"补偿温度"(β), 鉴定蛋白质在疏水相互作用色谱中保留机理的同一性。     

多氯联苯分子结构参数与色谱焓、熵变化的定量关系

 通过理论分析与研究,提出了描述多氯联苯(PCBs)氯原子数目与取代位置有关的分子拓扑指数结构参数JG以及描述多氯联苯分子中氯原子之间相邻关系的分子拓扑指数邻接参数LJ,并推导出PCBs在色谱过程中的焓变(ΔH)、似溶解熵变(ΔS′)与结构参数JG、邻接参数LJ的关系式。在DB-1,DB-5,DB-1701等3种固定相上测定了140余种PCB的ΔH、ΔS′数值,并运用所推导出的关系式对ΔH和ΔS′进行了预测,收到良好的效果,ΔH和ΔS′的理论计算值与实验值的平均相对偏差分别为0.56%~0.97%和0.55%~1.06%，接近实验数据本身的相对偏差。     

盐类和温度对非离子型表面活性剂溶液粘度的影响

研究在各种盐类存在下,温度对非离子表面活性剂(OP类)溶液粘度的影响,发现相对粘度的对数值与1/T呈线性关系,从直线的斜率可得活化自由能ΔG′。由热力学关系式可计算粘性流体的活化焓ΔII′和活化熵ΔS′。用所得热力学函数对胶束型态的转化进行了讨论。     

外偶极电场作用下H_2O,D_2O和T_2O的可逆分解电压

采用密度泛函B3P86方法和6-311++G(3df,3pf)基组,计算了在-0.05～0.05a.u.外偶极电场作用下,H2O,D2O,T2O,H2,D2,T2,O2的电子能量、核运动能量和熵值,在此基础上通过计算H2O(g)→H2(g)+O2(g)、D2O(g)→D2(g)+O2(g)、T2O(g)→T2(g)+O2(g)的焓变ΔH、熵变ΔS、Gibbs函数变化ΔG,最后得到了H2O,D2O,T2O的可逆分解电压Er.计算结果表明,外偶极电场存在时,H2O,D2O,T2O的Gibbs自由能变ΔG和可逆分解电压Er都有明显的变化,当外偶极电场正方向增加时,其Gibbs自由能变ΔG和可逆分解电压Er均趋于线性增加;当外偶极电场负方向增加时,其Gibbs自由能变ΔG和可逆分解电压Er均趋于线性减小;在相同外偶极电场作用下,Gibbs自由能变ΔG和可逆分解电压Er随H2O,D2O,T2O依次增加.     

蛋白质在固定Zn2+金属螯合亲和色谱中的变性热力学

在15~85℃宽温度范围,研究了蛋白质在固定Zn2 金属螯合色谱系统中的热行为和变性热力学。实验结果表明,蛋白质在色谱过程都有一个固定的热转变温度:核糖核酸酶(RNase)、α-胰凝乳蛋白酶原A(α-Chy)的热转变温度约为55℃,细胞色素C(Cyt-C)和溶菌酶(Lys)约为65℃;,热转变温度的出现标志蛋白质构象发生变化;利用Van′tHoff作图测定了蛋白质在色谱系统热变性时的标准焓变ΔH°和标准熵变ΔS°,提出用标准熵变ΔS°和自由能变ΔG°判断蛋白质构象变化;利用ΔH°-ΔS°的线性关系估算了蛋白质热变性时的补偿温度,鉴定了蛋白质各变体在金属螯合色谱中保留机理的同一性,RNase、Cyt-C、Lys和α-Chy的补偿温度分别为55℃、65.8℃、65.2℃和54.8℃;根据蛋白质热变性时的补偿温度和构象变化熵变Δ(ΔS°)的大小,讨论了蛋白质在阳离子交换色谱和固定Zn的金属螯合色谱体系中的热稳定性。实验证明,在IDA裸柱引入Zn2 后蛋白质在色谱系统中的热稳定性减小,平均补偿温度从65.3℃降低到59.7℃,而构象变化熵变的绝对值大幅度升高。     

LaFe13-xSix (1.2≤x≤2.2)化合物的磁场诱导熵变与磁场的关系

通过真空电弧熔炼、长时间真空热处理的方法获得了单相NaZn13-型LaFe13-xSix(1.2≤x≤2.2)化合物,并测量了它们的磁化强度与磁场和温度的关系,用Maxwell关系式计算出在不同磁场下化合物的熵变ΔS。用Landau的二级相变理论及平均场近似下的标度律,分析拟合了LaFe13-xSix化合物ΔS与H之间的关系,对于具有一级和二级相变的材料,发现均存在ΔS∝H2/3的关系,只是拟合得到的参数不同。采用熵变峰值拟合得到的参数能够反映材料中一级磁性相变的程度,研究磁场诱导的熵变与磁场的关系可以为磁制冷研制提供指导。     

PuH2气态分子热力学稳定性的理论研究

用密度泛函B3LYP方法计算了PuH2分子的微观性质、不同温度下气态PuH2分子的能量（E）、熵（S）及气态PuH2分子生成反应的标准焓变ΔH、标准熵变ΔS和标准自由能变ΔG.计算结果表明，气态PuH2分子不具有热力学稳定性.     

应用离子选择性电极进行溶液热力学研究 Ⅴ:KCl在283.15K～318.15K间七个温度下由H~2O至DMF-H~2O混合溶剂的标准转移Gibbs自由和转移熵的测定

本文应用Corning一价阳离子选择电极与氯离子选择电极组成无液接可逆电池,测定电池在283.15K～318.15K间七个温度下的标准电动势及其温度系数,计算KCl从纯水到相应的DMF-H~2O混合溶剂的标准转移Gibbs自由能ΔG 和标准转移熵ΔS ,得出ΔG 和ΔS 随混合溶剂中DMF的摩尔分数x~DMF及温度T的变化规律.发现KCl的ΔS随x~DMF变化的趋势和NaCl的相反.从离子溶剂化作用及其对溶剂结构的影响作了讨论.     

应用离子选择性电极进行溶液热力学研究 Ⅴ:KCl在283.15K～318.15K间七个温度下由H~2O至DMF-H~2O混合溶剂的标准转移Gibbs自由和转移熵的测定

本文应用Corning一价阳离子选择电极与氯离子选择电极组成无液接可逆电池,测定电池在283.15K～318.15K间七个温度下的标准电动势及其温度系数,计算KCl从纯水到相应的DMF-H~2O混合溶剂的标准转移Gibbs自由能ΔG 和标准转移熵ΔS ,得出ΔG 和ΔS 随混合溶剂中DMF的摩尔分数x~DMF及温度T的变化规律.发现KCl的ΔS随x~DMF变化的趋势和NaCl的相反.从离子溶剂化作用及其对溶剂结构的影响作了讨论.     

气液色谱法研究双-(O,O′-二正辛基二硫代磷酸酯)合镍(Ⅱ)与伯醇加合反应的热力学性质

本文用气液色谱法研究了 Ni[(C_8H_(17)O)_2PS_2]_2与 C_1—C_4伯醇加合反应的热力学性质.测定了317—353K 范围内加合反应的平衡常数,用作图法求得反应的ΔH和ΔS.ΔH、ΔS 与伯醇的碳原子数之间呈线性关系:-ΔH=11.8+4.57X (kJ/mol)-ΔS=30.6+16.4X (J/mol·K)用静电作用模型描述了加合物成键的实质.加合反应的平衡常数可以用经验公式描述:lgK=-1.601-0.8572X+(619.1-237.8X)/T     

二氧化碳和丙烯直接合成甲基丙烯酸的NiPMo/TiO2催化剂的研究

用溶胶-凝胶法以磷钼酸(MPA)的镍盐溶液水解钛酸四丁酯制备了NiPMo/TiO2催化剂.使用ICP、 XRD、 TG-DTA、 IR、 TPD-MS和微反应技术研究了催化剂的化学组成、热稳定性、化学吸附性质和催化反应性能.杂多钼酸盐与TiO2通过O2-在TiO2表面发生了键合.在623 K下,杂多阴离子仍保持原有的Keggin结构.CO2在Lewis酸位Ni(Ⅱ)和Lewis碱位Ni-O-Mo的桥氧协同作用下生成CO2卧式吸附态Ni(Ⅱ)←O-(CO)←(O--Ni).丙烯有多种吸附态在催化剂上吸附.在563 K、 1 MPa和空速1500 h-1的反应条件下,丙烯的摩尔转化率为3.2%,产物MAA选择性为95%.     

Synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives

Different approaches for the synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives from simple amino acids have been investigated. A library of 33 precursors for the preparation of N-hydroxy pyrazinones was obtained in moderate to good yields.     

α-Amino acid derived enaminones and their application in the synthesis of N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates and other heterocycles

A new and simple synthesis of novel N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates, which exist in equilibrium with their 4-oxo tautomers, has been developed in two steps starting from N-protected α-amino acids. The key intermediates are enaminones, which can also be isolated, characterized, and used for the construction of other functionalized heterocycles, before they spontaneously decompose to pyrrole products. 4-Hydroxypyrroles are prone to partial aerial oxidation but can be efficiently alkylated or reduced to stable polysubstituted pyrrolidine derivatives.     

Specific intramolecular aromatic CH insertion of diazosulfonamides

The chemoselectivity in the intramolecular CH insertion of various diazosulfonamides has been experimentally studied. The results reveal that the aliphatic 1,4-, 1,5-, or 1,6-C(sp³)?H insertions of diazosulfonamides are not accessible, while the aromatic 1,5-C(sp²)?H insertion can be realized specifically by adjusting the diazo-adjacent group. In addition, the general chemoselectivities in the intramolecular CH insertions of diazosulfonyl compounds are summarized. Generally, diazosulfones undergo both aromatic 1,5-C(sp²)?H and aliphatic 1,5- and 1,6-C(sp³)?H insertions, while diazosulfonates undergo aliphatic 1,5- and 1,6-C(sp³)?H insertions. However, diazosulfonamides only undergo aromatic 1,5-C(sp²)?H insertion.     

A general and convenient synthesis of 4-(tosylmethyl)semicarbazones and their use in amidoalkylation of hydrogen,heteroatom, and carbon nucleophiles

A general synthesis of previously unknown semicarbazone-based α-amidoalkylating reagents, 4-(tosylmethyl)semicarbazones, has been developed. The synthesis involved three-component condensation of semicarbazones of aliphatic or aromatic aldehydes with the same or other aldehydes and p-toluenesulfinic acid. The scope and limitations of this reaction were investigated. The compounds obtained were demonstrated to be an efficient α-(4-semicarbazono)alkylating agents. They were reacted with H- (sodium borohydride), O- (sodium methylate), S- (sodium phenylthiolate), N- (pyrrolidine, sodium succinimide), P- (trialkyl phosphites), and C-nucleophiles (sodium diethyl malonate) to give the corresponding products of the tosyl group substitution, 4-substituted semicarbazones, including analogues of nitrofurazone. Among the prepared compounds tested in vitro for antibacterial and antifungal activity, three nitrofuryl-containing semicarbazones exhibited high biological activities with minimum inhibitory concentration (MIC) values of 8–32 μg/mL.     

Toward new camptothecins. Part 6: Synthesis of crucial ketones and their use in Friedländer reaction

In the context of the preparation of camptothecin and luotonin A analogs, the synthesis of some key keto-precursors and their use in Friedländer condensation are described. This paper also focuses on the stability of these keto intermediates and emphasizes the major differences between indolizinones and pyrroloquinazolinones series. Noteworthy is also the report of some original structures isolated as by-products of some experiments.     

Synthesis of novel chiral bidentate hydroxyalkyl-N-heterocyclic carbene ligands and their application in palladium-catalyzed Mizoroki–Heck couplings and asymmetric addition of diethylzinc to benzaldehyde

A small library of new chiral bidentate hydroxyalkyl-imidazolium salts 1 is conveniently synthesized on multi-gram scale from inexpensive and commercially available chiral pool amino acids. The corresponding carbenes, generated by deprotonation of imidazolium salts 1, in combination with palladium(II) chloride were tested in the Mizoroki–Heck coupling reaction. The most significant results in terms of yields and reactivities were achieved with low catalyst loading. The catalytic activities of these imidazolium salts were also investigated in the asymmetric addition of diethylzinc to benzaldehyde. The use of MgO nanoparticles as an additive in conjunction with these ligands played a crucial role in increasing the efficiency of these reactions.     

N-Heterocyclic carbene-palladacyclic complexes: synthesis,characterization and their applications in the C-N coupling and α-arylation of ketones using aryl chlorides

N-Heterocyclic carbene-palladacyclic complexes 3 were successfully achieved in a one-pot procedure under mild conditions. The structure of 3a was unambiguously confirmed by X-ray single crystal diffraction and it was an active catalyst in the Buchwald-Hartwig amination and α-arylation of ketones even at very low catalyst loadings (0.01?mol%).     

Iodine-mediated oxidative Pictet-Spengler reaction using terminal alkyne as the 2-oxoaldehyde surrogate for the synthesis of 1-aroyl-β-carbolines and fused-nitrogen heterocycles

An efficient iodine-mediated oxidative Pictet-Spengler reaction in dimethyl sulphoxide (DMSO) using terminal alkynes as the 2-oxoaldehyde surrogate for the synthesis of aryl (9H-pyrido[3,4-b]indol-1-yl)methanones is described. The scope of the protocol includes the total synthesis of Fascaplysin, Eudistomins Y₁ and Y₂. The methodology is extended for preparing pyrrolo[1,2-a]-quinoxaline and indolo[1,5-a]quinoxaline derivatives. The utility of 1-aroyl-β-carbolines was demonstrated by performing palladium-catalyzed β-carboline directed ortho-C(sp2)-H functionalization of the phenyl ring with thiomethyl (SMe) group using DMSO as source and for accessing 4-aryl-canthin-6-ones.     

Facile synthesis of bicyclic 1-arylpyrazol-5-ones

In this Letter, we described a facile method for constructing fused bicyclic 1-arylpyrazol-5-one ring system. We employed various methylene-containing carboxylic acids as the substrates and proved that the pyrazolone ring closure requires activated methylene group in intermediate II. Accordingly, a series of structurally diversified, fused bicyclic 1-arylpyrazol-5-ones was prepared in moderate to high yields using the requisite substrates.