铁硫蛋白和钼铁硫蛋白的结构化学

一、引言比较普遍存在于生物体内的元素大约有30种,其中金属元素17种,它们存在的普遍性如表1所示。这些金属元素与肽链组成一系列的金属蛋白。由于含金属的生物分子在生命中起着丰富多采的作用,而引起生物、化学和物理等领域的科学家的广泛兴趣。近年来已逐渐     

金属蛋白的提取分离技术

微量元素在生命活动中起着十分重要的作用。体内微量元素(主要指金属元素)水平的反常、存在形态的变化以及特定的金属酶、金属蛋白的表达、定位、结构和功能等方面的变化常常与某些病理状态相关,甚至是关键的病理环节,所以对生物体系中金属蛋白的定位、含量、化学形态及其结构的高通量分析是生命科学研究领域的重要课题。本文介绍并比较了各种金属蛋白的提取、分离方法(包括高效液相、毛细管电泳和电泳技术)及与之对应的元素分析技术(包括激光剥蚀(LA)-等离子体电感耦合质谱(ICP-MS)、同步辐射(SR)-X射线荧光(XRF)技术等),主要介绍了各种电泳方法在金属蛋白分离中的应用。同时评价各种方法对蛋白结合金属的影响,针对方法的局限性提出了可能的解决办法。     

西红花中金属元素的分析

西红花为鸢尾科植物番红花(Crocus sativus L)的干燥柱头.具活血化瘀,凉血解毒,解郁安神等功效.采用原子吸收分光光度法(AAS)测定西红花中部分金属元素的含量,通过对其宏量元素及微量元素含量的测定结果,分析了西红花中金属元素及其生理作用与药用功效之间的关系.随着元素医学的不断发展,金属元素与中药药效关系及对生物体系的作用有待研究.     

分离对映体用的新型固定液(摘要)

自然界中有许多物质均以对映体结构而存在。由于地球上生物体内的物质多系L型,在分析外层空间物质时,为考察地球以外是否有生命存在,就应当考虑从外层空间所取得的样品(如陨石、月球上取回的样品)有否受到大气层的沾污,就必须根据样品中所含有的L型或D型物质的多少来作出判断。     

金属和非金属元素的甲基化行为其在环境化学研究中的意义

甲基化过程是许多金属元素与生物地球化学循环的重要途径,目前已知多种金属,非金属元素在自然界中均匀甲在化反应过程,在前人工作的基础上,本文对甲基化供体以及甲化反应的机理进行了论述,并对其在环境化学研究中的意义进行了讨论。     

一维链状锌配位聚合物[Zn(4，4′-bipy)·(o-ABA)2·(H2O)2]n的合成、晶体结构及热稳定性

锌是重要的生命元素,在生物体内锌以多种形式参与代谢过程,包括糖类、脂类、蛋白质与核酸的合成与降解,对生命体系有着特殊的生物活性和催化作用[1].模拟合成以锌、铜等为中心离子的配位聚合物并对其结构进行研究,将为人们认识生命体系中与这些金属离子相关的生命现象提供重要的信息[2,3].4,4′-联吡啶是一种线状双基刚性配体,无支链,空间位阻少,有较好的桥联作用,它与金属离子在自组装过程中能形成各种一维,二维,及三维空间结构的配位聚合物[4～7].     

光学异构体拆分方法的进展

光学活性异构体物质广泛存在于自然界的生物体内,为生命起源的基本物质。蛋白质和酶等物质,就是由许多光学活性的氨基酸组成。     

红外吸收光谱法测定土壤中碳和硫

碳是构成生命的重要元素,环境中的碳不仅是生命元素,也是植物的营养和调节元素,是自然界中生命及其有机物的重要组分,并在有机物的合成、转化和调节植物体内的生理现象以及对环境的影响等方面起着重要作用。硫是构成含硫氨基酸和蛋白质的基本元素,     

帕金森病中的关键金属元素

随着我国人口日趋老龄化,老年退行性疾病呈高发态势,据估计当今我国帕金森病患者占世界一半左右。因此,帕金森病日益成为危害我国人民生命健康的突出问题之一。当前临床上对帕金森病无有效治愈手段,而且对于帕金森病的发病机制仍无定论。在诸多可能的诱因中,过渡金属元素的内稳态失衡和氧化应激,被认为与帕金森病相关。本文以生物体两种必需的过渡金属元素铁和铜为中心,介绍了与细胞内铁元素和铜元素代谢相关的信号通路和基因蛋白,并阐述了铁元素或铜元素稳态失衡对神经细胞造成损伤的可能机制。最后,介绍了同步辐射技术应用于帕金森病中元素分析和机制的研究进展,并展望了帕金森病中生物无机问题的未来研究方向。     

金属在生物和医学中的作用

金属元素在整个生命体系中起着重要的作用。金属离子与核酸、蛋白质等生物大分子的作用以及对神经系统的不正常的影响可以直接或间接地损伤DNA从而引起细胞的变异,进而导致各种疾病;同时我们可以根据这些特性研究金属离子的药物用于各种疾病的诊断和治疗。本文着重介绍了几种重要的金属和无机药物。     

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.     

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.     

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.