Comparisons of NMR spectral quality and success in crystallization demonstrate that NMR and X-ray crystallography are complementary methods for small protein structure determination

X-ray crystallography and NMR spectroscopy provide the only sources of experimental data from which protein structures can be analyzed at high or even atomic resolution. The degree to which these methods complement each other as sources of structural knowledge is a matter of debate; it is often proposed that small proteins yielding high quality, readily analyzed NMR spectra are a subset of those that readily yield strongly diffracting crystals. We have examined the correlation between NMR spectral quality and success in structure determination by X-ray crystallography for 159 prokaryotic and eukaryotic proteins, prescreened to avoid proteins providing polydisperse and/or aggregated samples. This study demonstrates that, across this protein sample set, the quality of a protein's [15N-1H]-heteronuclear correlation (HSQC) spectrum recorded under conditions generally suitable for 3D structure determination by NMR, a key predictor of the ability to determine a structure by NMR, is not correlated with successful crystallization and structure determination by X-ray crystallography. These results, together with similar results of an independent study presented in the accompanying paper (Yee, et al., J. Am. Chem. Soc., accompanying paper), demonstrate that X-ray crystallography and NMR often provide complementary sources of structural data and that both methods are required in order to optimize success for as many targets as possible in large-scale structural proteomics efforts.     

四磺化酞菁钴在微乳液、醇-水体系中的二聚现象研究

采用分光光度法研究了四磺化酞菁钴（ＣｏＴＳＰｃ），在微乳液（ＴｒｉｔｏｎＸ－１００－壬烷－正戊醇－水）、醇－水（甲醇、乙醇、丙醇）体系中的二聚现象，计算了ＣｏＴＳＰｃ的二聚常数ＫＤ。结果表明，ＣｏＴＳＰｃ的二聚常数ＫＤ值随着微乳液中表面活性的浓度及醇－水溶液的介电常数的增加而减小。     

La2O3对Ni/γ-Al2O3甲烷化催化剂的助催化作用

我国将稀土作为助剂引入镍基甲烷化催化剂,大大提高了催化剂的活性和热稳定性,并已投入工业应用［1－3］．稀土对不同镍催化剂反应性能及其作用机理的研究已有一些报导［3－7］．谢有畅等观察到镍负载在经单层La2O3改性的γ－Al2O3表面,其晶粒要比没有La2O3时小得多．Rotgerink等认为添加La后反应速率的增加不只是由于几何效应,而是La对甲烷化本身有促进作用,单位镍表面的活性是随La含量不同而改变的,活性增加的同时表观活化能也增加［5］．作为助剂的La2O3在氢还原和反应过程中的变化及其作用的研究和讨论较少,目前一般认为添…     

Use of on-line mass spectrometric detection in capillary electrochromatography

Capillary electrochromatography (CEC) is a liquid phase analytical separation technique that is generally carried out with packed capillary columns by electroosmotically driven mobile phase at high electric field strength. The analytes are separated by virtue of the differences in their distribution between the mobile and stationary phases and, if charged in their electrophoretic mobilities as well. It is thus considered a hybrid of liquid chromatography and capillary electrophoresis and is expected to combine the high peak efficiency of capillary zone electrophoresis (CZE) with the versatility and loading capacity of HPLC. This review explores the potential use of on-line mass spectrometric detection for CEC. It discusses key design issues that focus on the physical and electrical arrangement of the CEC column with respect to the electrospray orifice inlet. The salient features of the sheathless, sheath flow and liquid junction interfaces that are frequently employed while coupling a CEC column to an electrospray ionization mass spectrometry system are also highlighted. Possible configurations of the CEC column outlet that would obviate the need for pressurizing the capillary column are also presented. While coupling CEC with MS both the nature of the interface and the configuration of the column outlet will determine the optimal arrangement. The review also discusses bandspreading that occurs when a connecting tube is employed to transfer mobile phase from the column outlet to the atmospheric region of the electrospray source with a concomitant loss in sensitivity. Selected examples that highlight the potential of this technique for a wide range of applications are also presented.     

双8-羟基喹啉端开链冠醚金属络合物的光物理性质

设计合成了双8-羟基喹啉端的开链冠醚QP3Q,研究了金属离子铝或锌与其形成络合物的组成和发光性质,并测定了络合物的激发态寿命.这些络合物在溶液中有较高的荧光量子产率,所得到的络合物固体具有较强的蓝光发光性能.结果表明,有可能通过QP3Q与不同离子形成的络合物得到不同发光波长的发光材料.     

聚吡咯水杨酸修饰电极的电化学行为及水杨酸含量测定

本用电化学方法制备了聚吡咯－水杨酸修饰电极；并进行了电化学行为的研究，经电化学处理该是电极对水杨酸根具有选择性响应，响应线性范围在１．０×１０＾－＾５－１．０×１０＾－＾３ｍｏｌ／Ｌ之间。电极斜率为４０ｍＶ／ｐＣ，该电极具有较好的稳定性，响应时间在１８０－３００ｓ之间；电极寿命可达６０ｄ。     

同步辐射白光全反射XRF在痕量元素检测的初步应用研究

叙述了同步辐射白光全反射Ｘ射线荧光分析的实验装置，给出了几种标准物质ＴＸＲＦ实验的检出限，并对实验结果进行了讨论。     

An Efficient and Green Synthesis of 5-Oxo-5, 6, 7, 8-tetrahydro- 4H-benzo-[b]-pyran Derivatives Promoted by InCl_3·4H_2O Under Microwave Irradiation

Construction of tetrahydropyran rings has attracted a great deal of interests in organic synthesis in recent years1, since tetrahydropyran moiety constitutes a structural unit in a number of natural products2. In addition, tetrahydropyran derivatives possess wide range of biological activities and pharmacological properties, such as anticancer activity3 and antihypersensitivity4. Many methods for the preparation of such compounds have already been developed5. Among them, condensation of α, β…     

脱氧核糖核酸在汞膜电极上的电化学行为

首次在汞膜电极上利用循环安，微分脉冲和交流伏安法研究脱氧核糖核酸（ＤＮＡ）的电化学行为，结果表明汞膜电极作为一类固体电极可应用于负电位区ＤＮＡ电化学行为的研究。同时结合凝胶电泳和ＵＶ光谱法，研究了用纯高氯酸处理的ＤＮＡ的氧化还原特性，结果表明纯高氯酸可经起ＤＮＡ的变性和降解，纯高氯酸不适宜ＤＮＡ的变性处理。     

丙烯环氧化反应的高活性钼催化剂

在钼(Ⅵ),钒(Ⅴ)和钛(Ⅳ)等化合物存在下,丙烯与烷基过氧化氢的环氧化反应比传统的氯醇法有很多优点,其中以钼催化剂的性能最优,但目前报道的催化剂在反应过程中因易分解而降低了活性,并且丙烯与烷基过氧化氢的投料比过大(>3:1),丙烯循环次数过多。前文报道了钼烷基醇胺化合物对环已烯的环氧化反应,本文考察了钼烷基醇胺化合物对丙烯与叔丁基过氧化氢环氧化反应的催化性能。