蛋白质酪氨酸硝化的研究

蛋白质酪氨酸硝基化是一种重要的蛋白质翻译后修饰,与多种病症相关。经由过氧亚硝酸根(ONOO-)和NO2-/H2O2/血红素过氧化物酶体系是促使蛋白质硝化最主要的两种途径,其反应为自由基机理。本文对体内蛋白质硝基化的途径、机制及其生物学意义作了综述,指出蛋白质的硝化具有选择性,特定酪氨酸残基发生硝化能够改变蛋白质的结构和功能,影响其免疫应答和可能涉及的信号转导过程,从而具有重要的生物学意义。     

蛋白质酪氨酸硝化的研究

蛋白质酪氨酸硝基化是一种重要的蛋白质翻译后修饰,与多种病症相关.经由过氧亚硝酸根(ONOO-)和NO2-/H2O2/血红素过氧化物酶体系是促使蛋白质硝化最主要的两种途径,其反应为自由基机理.本文对体内蛋白质硝基化的途径、机制及其生物学意义作了综述,指出蛋白质的硝化具有选择性,特定酪氨酸残基发生硝化能够改变蛋白质的结构和功能,影响其免疫应答和可能涉及的信号转导过程,从而具有重要的生物学意义.     

蛋白质酪氨酸硝化检测方法*

蛋白质酪氨酸硝化是一种重要的蛋白质翻译后的选择性修饰,其产物3－硝基酪氨酸可以作为检测细胞和组织损伤的一个生物标志。本文详细介绍了分析检测蛋白质酪氨酸硝化的各种方法,主要包括免疫法、分光光度法、色谱法、质谱法、电泳法等,并对其检测方法的发展趋势进行了评述和展望。     

微量元素铁与蛋白质酪氨酸硝化

蛋白质酪氨酸硝化是一氧化氮依赖的氧化应激的生物标志。蛋白质硝化将会直接影响蛋白质的催化活性、细胞信号传递和细胞骨架结构,导致相关病症的发生发展。本文介绍了铁在不同酪氨酸硝化途径中的作用,结果提示体内的微量铁对蛋白质硝化起着重要作用。     

基于离心式富集装置的酪氨酸磷酸肽分析新方法

酪氨酸磷酸化及其相应激酶活性的研究在抗肿瘤药物靶点的研发中具有重要意义.由于酪氨酸磷酸化仅占蛋白质总磷酸化含量的不足0.1%,因此规模化的酪氨酸磷酸化鉴定面临着重大技术挑战.本研究构建了TiO2串联C18反相填料的离心式富集装置,结合抗体免疫沉淀法,建立了酪氨酸磷酸肽的富集策略.此新型富集装置由吸头、适配器和离心(EP)管组成,将TiO2富集磷酸肽和C18填料反相分离磷酸肽有机结合,以离心的方式进行样品的上样、清洗、洗脱和分离,再通过抗酪氨酸磷酸化抗体进一步特异性富集酪氨酸磷酸肽,从而实现了酪氨酸磷酸肽的高效富集和大规模质谱鉴定.通过离心式富集装置简化了实验步骤,减少了样品损失和人为因素干扰;而且离心式、平行化的样品处理方式可显著提高分析通量.将此策略成功用于小鼠肝脏蛋白质酪氨酸磷酸化肽段的富集和质谱鉴定,在5 mg鼠肝蛋白中共鉴定出967个酪氨酸磷酸化位点,对应545个蛋白质,显示了其在蛋白质组学研究中的应用潜力.     

蛋白质相互作用界面中磷酸酪氨酸质子化状态的判定研究

蛋白质相互作用界面上磷酸酪氨酸的质子化状态对蛋白质相互作用具有重要影响, 在进行相关结构的计算研究时, 必须对其进行准确判定. 采用AMBER/parm99力场和广义波恩(GBobc)隐式水模型, 以SHC1 (src homology 2 domain-containing transforming protein C1)的SH2 (Src homology 2)结构域与磷酸化激活的T细胞受体CD247链的相互作用核磁结构为例, 首次以热力学积分方法对相互作用界面上磷酸酪氨酸的质子化状态进行判定研究, 结果显示该方法计算精确, 判定结果与实验结果一致. 表明该方法不仅为涉及磷酸酪氨酸的蛋白质相互作用的计算结构研究奠定了基础, 在其它具有可电离基团的氨基酸的质子化状态判定中也将具有潜在的推广应用价值.     

荧光光度法测定血清中酪氨酸

酪氨酸在人体内虽是一种非必需氨基酸.但其含量稳定与否会影响人体健康状况,而且其含量是疾病检测的一个指标,所以准确地测定体液中酪氨酸具有重要的意义.荧光法测定酪氨酸已有文献报道.我们发现在酸性介质中铈(Ⅳ)可将酪氨酸氧化为强荧光性物质,以此可作为酪氨酸荧光定量分析的基础.     

L-酪氨酸甲酯消旋及Alcalase 2.4L催化对映选择性水解制备D-酪氨酸

提出了一个5-硝基水杨醛催化L-酪氨酸甲酯消旋化的新方法并推测了L-酪氨酸甲酯的消旋机理.在乙腈/磷酸盐缓冲液(pH 7.5)中,5-硝基水杨醛催化L-酪氨酸甲酯消旋为DL-酪氨酸甲酯,消旋率100%,消旋收率93%.优化了Alcalase 2.4L催化DL-酪氨酸甲酯对映选择性水解的反应条件.30℃下,在叔丁醇/磷酸盐缓冲液(pH 7.5)中,Alcalase 2.4L催化DL-酪氨酸甲酯对映选择性水解为L-酪氨酸和D-酪氨酸甲酯.在酶催化水解过程中,L-酪氨酸形成沉淀,容易通过简单的过滤进行分离.D-酪氨酸甲酯在碱性条件下水解为D-酪氨酸,收率91%,ee97%.     

阻抑速差催化光度法测定痕量色氨酸和酪氨酸

研究了色氨酸、酪氨酸在硫酸环境中抑制碘对亚砷酸与硫酸铈氧化还原反应的催化作用及动力学条件。在0．001mol／L Ce(SO4)2,0．00125mol／L As2O3,0．013mg／L KI,0．025g／L和0．25g／L NaCl溶液中测定色氨酸和酪氨酸,其线性范围分别为0．0～0．65mg／L,0．0～4．0mg／L和0．0～1．3mg／L。0．10～4．0mg／L,用联立方程分别求出各自含量。用此法对醇溶蛋白质和混合氨基酸溶液中色氨酸和酪氨酸进行测定,混合氨基酸的色氨酸、酪氨酸测量值为0．8037g／L,3．591g/L;蛋白质的色氨酸、酪氨酸测量值为1．8g/kg、3．43g/kg;回收率在88％～109％;色氨酸和酪氨酸的RSD分别为4．8％和5．2％,结果满意。     

HPLC-ESI-MS/MS测定胰岛素硝基化修饰产物

糖尿病患者组织中存在过量表达的ONOO-及3-硝基酪氨酸(3-NT),ONOO-对胰岛素的硝化修饰可能是糖尿病发病的重要原因.本实验采用HPLC-ESI-MS/MS及分子模拟法,研究了ONOO-与胰岛素反应的硝化产物、B链酪氨酸位点的硝化次序及硝化产物结构特征.     

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.     

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.     

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.     

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.