非水纳米分散系的冷冻蚀刻电镜表征及与激光散射法的对比研究

报道了利用改进的冷冻蚀刻制样技术对非水介质中原位合成的纳米分散系进行的电子显微镜表征结果。研究了冷冻蚀刻电镜技术观测原位合成纳米分散系的制样步骤、制样方法,并利用冷冻蚀刻电镜技术原位观测了3种纳米分散相的粒径、粒径分布和聚集状态。激光散射法与冷冻蚀刻电镜表征的对比表征结果表明：纳米分散系中纳米相的粒径和粒径分布用两种表征方法所得结果基本一致,但冷冻蚀刻电镜表征与激光散射法相比具有准确、直观、清晰、立体的特点,并且可同时采集多种信息。与激光散射法相比,是一种表征非水纳米分散系的理想方法。     

非水纳米分散系的冷冻蚀刻电镜原位观测

研究了冷冻蚀刻电镜技术原位观测合成的纳米分散系的制样步骤、制样方法,并利用冷冻蚀刻电镜技术原位观测了四种纳米分散系中分散相的粒度、粒度分布和聚集状态.研究结果表明:蚀刻时间对电镜照片图像质量有较大影响,蚀刻时间应根据分散系中分散相含量、粒度大小来选;冷冻蚀刻电镜用于原位观测非水纳米分散系,具有准确、直观、清晰、立体的特点,并且可同时采集多种信息.     

绵羊冷冻精液生化及超微结构研究

运用电子显微镜和酶法分析手段评定绵羊冷冻精液品质,建立了研究绵羊冷冻精液的电镜免染色法和超薄切片法。观察绵羊冷冻精液精子的超微结构,测定精子中透明质酸酶、谷种转氨酶、乳酸脱清酶的释放量,并着重研究这些指标与受胎率之间的相关性。本工作为绵羊冻精研究提供了可靠依据,为发展养羊业做出了贡献,为国内精液生理生化研究填补了一项空白。     

电子显微镜下的纳米世界

以高中阶段知识为基础,简述了扫描电子显微镜、透射电子显微镜等电镜技术的发展和基本原理,并以实际应用案例介绍了电镜技术在纳米科学领域的应用,最后给出了电镜技术的未来发展前景。     

结构生物学技术在线粒体钙离子单向转运体结构功能研究中的运用

线粒体钙离子单向转运体是一种位于线粒体内膜上的转运蛋白,具有选择和传导钙离子的功能,参与多种细胞的生理过程。目前已经确定了该单向转运体的组成成员,其中包括离子转运蛋白MCU、MCU的负调控亚基MCUb、2个Ca²⁺结合蛋白MICU1、MICU2以及MCU的调控亚基EMRE蛋白。近十多年来已经有大量的研究提出并构建了多种线粒体通过该单向转运体调节Ca²⁺摄取的模型。最近对其研究的重点转向单向转运体单个组分的结构以及对它们复合体的结构表征。这些问题的解决得益于结构生物学中核磁共振技术、X射线衍射技术的持续发展和冷冻电镜技术的突破。回顾了结构生物学技术在有关单向转运体结构问题过程中的综合运用。这一内容将有助于我们了解核磁共振、X射线晶体学以及冷冻电镜技术各自的优缺点,同时深入探究线粒体钙离子单向转运体各部分的结构及其发挥功能的分子机制。     

低温X射线晶体衍射法在生物大分子结构分析中的应用

综述了低温X射线晶体衍射法在生物大分子结构测定中的发展与应用，介绍了在数据收集中的急速降温，冷冻防护剂的使用和载晶技术, 以及低温X射线晶体衍射法应用于测定生物反应中间体的最新进展。     

基于镜像酶正交酶切的蛋白质复合物规模化精准分析新方法

蛋白质主要以复合物的形式参与各项生命活动.化学交联质谱(CXMS)技术作为近年来新兴的蛋白质复合物解析技术,不仅可实现蛋白质复合物规模化解析,而且普遍适用于任意相对分子质量和纯度的蛋白质复合物样品,因此已成为X-射线晶体衍射技术、冷冻电镜技术等蛋白质复合物解析经典技术的重要补充.目前,CXMS主要采用胰蛋白酶将交联后的...     

低反差样品电镜图像衬度的提高

介绍了低反差生物医学样品在其制备，电镜观察以及底片和片的冲洗过程中提高电镜图像衬度的方法。     

SDBS／正辛烷／正丁醇／盐水体系中相微乳液微观结构的研究

利用冷冻蚀刻电镜、ＦＴ－ＩＲ、ＥＳＲ和ＮＭＲ方法研究了ＳＤＢＳ／ｎ－Ｃ４Ｈ９ＯＨ／ｎ－Ｃ８Ｈ１８盐水体系中相微乳液微观结构。四种方法均表现随着体系含盐度的增加，中相微乳液微观结构经历了从Ｏ／Ｗ型到Ｂ．Ｃ型，再到Ｗ／Ｏ型的转变。     

CM200透射电子显微镜保护关机的故障分析及维修

介绍了CM200透射电子显微镜电镜保护(LPR)的工作原理,分析了电镜保护关机的故障原因并介绍了几个维修实例.     

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.     

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.     

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.     

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.     

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.     

CoFe2O4自形成磁性液体场致结构化对磁化的影响

The Langevin paramagnetic theory can’t describe the relation between magnetization of ferrofluids and applied magnetic field. The structuralization of ferrofluids, which is considered the main influence factor of the magnetization, is regarded. The part of magnetization works is deposited when the structure is forming. This action influences the magnetization of ferrofluids directly or indirectly. On the base of the “compressing” model, the Langevin function that usually describes the magnetization of ferrofluid is modified, and a well-fitted curve is obtained. An equation of the relation between the equivalent volume fraction after being “compressed” and the intensity of magnetic field is discovered, which approximately describes the process of magnetization. The relation between the approximate initial susceptibility and the volume fraction can be obtained from modified formula.     

Microwave-assisted copper-catalyzed stereoselective ring expansion of three-membered heterocycles with α-diazo-β-dicarbonyl compounds

Microwave-assisted copper-catalyzed ring expansions of three-membered heterocycles with α-diazo-β-dicarbonyl compounds were investigated. Thiiranes generated 3-acyl-5,6-dihydro-1,4-oxathiines in the presence of copper sulfate and trans-3-acyl-5,6-dihydro-1,4-oxathiines as stereospecific products for 1,2-disubstituted cis-thiiranes through an intramolecular S_N2 process. Oxiranes gave rise to 2-acyl-5,6-dihydro-1,4-dioxines under the catalysis of copper hexafluoroacetylacetonate and cis-3-acyl-5,6-dihydro-1,4-dioxines as stereospecific products for 1,2-disubstituted cis-oxiranes via an intimate ion-pair mechanism. The current method provides a direct and simple strategy in efficient preparation of 3-acyl-5,6-dihydro-1,4-oxathiines and 2-acyl-5,6-dihydro-1,4-dioxines, important agents in medicinal and agricultural chemistry, from readily available thiiranes and oxiranes, respectively.     

KMnO4-mediated oxidative CN bond cleavage of tertiary amines: Synthesis of amides and sulfonamides

KMnO₄-mediated oxidative CN bond cleavage of tertiary amines producing secondary amine was introduced, which was trapped by electrophiles (acyl chloride and sulfonyl chloride) to form amides and sulfonamides. The reaction could take place at mild condition, tolerating a wide range of function groups and affording products in moderate to excellent yields.