老鼠Tet1蛋白能氧化单链脱氧核糖核酸上的5-甲基胞嘧啶到5-羟甲基胞嘧啶和5-羧基胞嘧啶(英文)

5-甲基胞嘧啶在哺乳动物细胞中具有广泛的作用.而它被双脱氧家族Tet蛋白氧化所得的产物5-羟甲基胞嘧啶、5-醛基胞嘧啶和5-羧基胞嘧啶也被证明在细胞发育和5-甲基胞嘧啶动态平衡调控中具有关键的作用.已有的研究结果表明,Tet蛋白能够识别双链DNA上的5-甲基胞嘧啶,并将其氧化成5-羟甲基胞嘧啶、5-醛基胞嘧啶和5-羧基胞嘧啶.我们通过质谱仪检测发现,老鼠Tet1蛋白的DNA结合结构域还能识别和氧化单链DNA上的5-甲基胞嘧啶.这一发现暗示我们,Tet蛋白家族不但具有已经发现的氧化双链DNA上5-甲基胞嘧啶的功能,还有可能作用于DNA的复制及转录,甚至具有氧化单链RNA上对应的甲基修饰碱基的能力.     

Peptide Inhibitors of HIV-1 Virus Infection Based on Cullin-5

Virion infectivity factor（Vif） is one of the six accessory proteins of HIV-1 and is necessary for viral infectivity. Human Apolipoprotein B editing complex protein 3G（h-APOBEC3G） is a cytidine deaminase only expressed in ＂nonpermissive＂ cells and exhibits virus suppressive activity. With the aid of a Cullin-5 E3 ligase, Vif induces h-APOBEC3G degradation and with the destruction of this ligase, Vif is functionally inactive. Therefore, it is expected that blocking this E3 pathway would be a new therapeutic strategy against HIV-1 infection. In this article, the authors＇ took sequence alignment of the N-termini of Cullin-5 and three other members of the Cullin protein family, respectively. A set of small peptides has been synthesized based on the sequence comparison results and possible Vif-Cullin-5 interaction domains. Moreover, it has been demonstrated that several peptides can reduce virus infectivity in ＂nonpermissive＂ cells with a dose-responsive manner, but not in ＂permissive＂ cells. The results also indicate that the loss of viral infectivity may be because of the increase of APOBEC3G amount in the peptide-treated cells. It is concluded that peptides derived from Cullin-5 can block the APOBEC3G degradation induced by Vif and suppress HIV-1 infectivity. Therefore this study starts a novel strategy for the development of a new HIV-1 inhibitor.     

用分子对接方法研究HIV-1融合酶与病毒DNA的结合模式

用分子对接方法研究了HIV-1整合酶（Integrase,IN）二聚体与3’端加工（3’Processing,3’-P）前的8bp及27bp病毒DNA的相互作用,并获得IN与27bp病毒DNA的特异性结合模式。模拟结果表明,IN有特异性DNA结合区和非特异性DNA结合区;IN二聚体B链的K14,R20,K156,K159,K160,K186,K188,R199和A链的K219,W243,K244,R262,11263是IN结合病毒DNA的关键残基;并从结构上解释了能使IN发挥活性的病毒DNA的最小长度是15bp。通过分析结合能发现,IN与DNA稳定结合的主要因素是非极性相互作用,而关键残基与病毒DNA相互识别主要依赖于极性相互作用．模拟结果与实验数据较吻合。     

用分子对接方法研究HIV-1整合酶与病毒DNA的结合模式

用分子对接方法研究了HIV-1整合酶(Integrase, IN)二聚体与3’ 端加工(3’ Processing, 3’-P)前的8 bp及27 bp病毒DNA的相互作用, 并获得IN与27 bp病毒DNA的特异性结合模式. 模拟结果表明, IN有特异性DNA结合区和非特异性DNA结合区; IN二聚体B链的K14, R20, K156, K159, K160, K186, K188, R199和A链的K219, W243, K244, R262, R263是IN结合病毒DNA的关键残基; 并从结构上解释了能使IN发挥活性的病毒DNA的最小长度是15 bp. 通过分析结合能发现, IN与DNA稳定结合的主要因素是非极性相互作用, 而关键残基与病毒DNA相互识别主要依赖于极性相互作用. 模拟结果与实验数据较吻合.     

HIV-1整合酶的RNA适配子的筛选及活性研究

通过SELEX技术已经筛选到了多种HIV-1病毒相关蛋白,如：逆转录酶、Rev和Tat蛋白、核壳蛋白等的核酸适配子,然而以HIV-1整合酶为靶点的DNA或RNA适配子却鲜有报道．在结合缓冲液中以10mmol．L-1的Mg2＋作为辅助因子,加入100mmol．L-1KCl筛选到了三个具有相似结构和托的适配子IN1,IN2和IN3．亲和力最高的适配子IN1的Kd为145nmol．L-1,保守区富含乌嘌呤碱基（G）,缺失任何一个茎环结构会使亲和力减弱．缺失右端固定序列的IN1-L的Kd为283nmol．L-1,虽然不能形成四链结构但可以被G-四链T40214竞争结合,可能与T40214具有相同的结合位点．     

结构多样的HIV-1整合酶抑制剂:过去、现在和未来

HIV-1整合酶是逆转录病毒复制的必需酶,它催化病毒DNA与宿主染色体DNA的整合,而且在人类细胞中没有类似物,因此成为治疗艾滋病的富有吸引力和合理的靶标.最近十年,一大批HIV-1整合酶抑制剂被鉴定出来,其中一些化合物显示选择性的抑制HIV-1整合酶和阻断病毒复制的活性,而最有影响的两类抑制剂是含邻苯二酚的多羟基芳环化合物和最近报道的芳基β-二酮酸类化合物.全面综述了用于HIV-1整合酶抑制剂研究以发展抗HIV新药的不同种类的化合物,包括苯并咪唑类衍生物、核苷类、多肽、羟基取代的芳环化合物及二酮酸类化合物等,并阐述了这些化合物中对抑制活性重要的结构特征.同时也介绍了HIV-1整合酶的结构、功能以及HIV-1整合酶抑制剂的设计原理和作用机制.     

荧光小分子2-氨基-5,6,7-三甲基-1,8-萘啶识别dsDNA中胞嘧啶凸出

双链DNA（dsDNA）中单碱基凸出结构（bulge structure）具有重要生物学意义,这种结构也是DNA靶向药物的目标部位之一.荧光小分子2-氨基-5,6,7-三甲基-1,8-萘啶（ATMND）能够通过氢键识别胞嘧啶（cytosine）,因而对dsDNA中凸出的胞嘧啶表现出明显的特异性结合.与其余三种凸出的碱基相比,ATMND与凸出部位胞嘧啶的结合伴随着ATMND荧光的明显猝灭,因而可以用于胞嘧啶凸出结构的识别.利用解旋温度测量、荧光、圆二色光谱对ATMND和存在胞嘧啶凸出结构的dsDNA相互作用进行了研究.荧光滴定结果表明ATMND和dsDNA中凸出部位未配对的胞嘧啶的结合常数K11=4.8×105M？1.通过对含胞嘧啶凸出结构的dsDNA与ATMND结合前后的解旋温度曲线进行解析,发现胞嘧啶凸出结构相邻碱基对凸出的胞嘧啶与ATMND的结合有较大的影响.荧光测量结果也表明ATMND荧光的猝灭效率与凸出结构相邻碱基的类型有关,当相邻碱基为鸟嘌呤（guanine,G）时,荧光猝灭效率最高.基于dsDNA中凸出的碱基对ATMND荧光猝灭效率存在明显差异这一现象,设计了探针DNA实现了乳腺癌相关基因（PGR gene rs3740753）中单核苷酸多态性（G/C变异）的荧光分型.     

靶向整合过程不同步骤的HIV-1整合酶抑制剂的结构类型和研究进展

HIV-1整合酶是病毒复制所必需的三个基本酶之一, 为病毒所特有, 人体无对应的酶, 因此整合酶是理想的抗HIV药物设计的新靶标. HIV-1整合酶催化病毒DNA插入宿主染色体的过程涉及到整合酶与前病毒DNA形成整合前复合物、病毒DNA的3’末端切断和DNA链转移等步骤, 目前研究得最多的HIV-1整合酶抑制剂是抑制链转移反应的芳基二酮酸化合物, 其中的电子等排体衍生物Raltegravir (MK-0518)于2007年10月被美国食品药品管理局(FDA)批准上市, 而GS-9137处于三期临床试验, 此外还有多个处于临床前研究和临床阶段的药物. 根据抑制剂的不同作用机理, 本综述介绍了近年来所报道的HIV-1整合酶抑制剂的结构类型、药效团模型、研究进展及化学合成, 将整合酶抑制剂分为链转移反应抑制剂、整合酶-DNA结合抑制剂、整合酶3’端切除反应抑制剂、非专一性整合酶抑制剂以及多肽类抑制剂等几大类. 其中链转移反应抑制剂结构类型最丰富、发展最快. 整合酶抑制剂的出现丰富了高效抗逆转录病毒疗法(HAART), 为多重抗药性艾滋病患者提供了新的有效的治疗方案.     

HIV-1病毒DNA与整合酶结合后的构象变化

用分子动力学(MD)模拟方法优化了HIV-1病毒DNA与整合酶(IN)二聚体(IN2)复合物模型结构, 并分析了HIV-1病毒DNA结合IN2后的构象变化. 结果表明, 按照HIV-1病毒DNA与IN2结合能力的强度, 病毒DNA可分为五个区域: 非结合区、强结合区1、弱结合区、强结合区2和反应区, 并用结合自由能计算验证了该分区的合理性. 与未结合IN2的病毒DNA相比, 复合物模型中病毒DNA除了非结合区碱基外, 其它四个区域的碱基构象变化较大. 复合物模型中病毒DNA主链较大程度地偏离标准B型DNA以及结合部位的小沟变宽都是识别IN的结构基础. 模拟结果与实验数据吻合较好, 为基于HIV-1 IN的药物分子设计提供了一定的结构信息.     

修饰组学:解析修饰生物分子功能

基因的时空表达通过转录、翻译和蛋白翻译后修饰这3个层面进行调控.目前在基因组DNA、RNA和蛋白质上发现了丰富的化学修饰.这些化学修饰被认为是调控基因时空表达的另一种新机制.截至目前,在核酸和蛋白质中已经分别发现了超过150和400种不同类型的修饰,阐明这些修饰的生理功能有助于促进对生命体调控机理和运行机制的认识和理解.包括基因组学、转录组学、蛋白质组学和代谢组学在内的组学研究已经蓬勃发展了几十年.鉴于DNA、RNA和蛋白质上含有丰富多样和具有调控作用的化学修饰,本文从修饰和组学的角度提出了新的概念:修饰组学.修饰组学主要是指对DNA修饰、RNA修饰和蛋白质修饰的系统和综合研究.本综述通过介绍DNA、RNA和蛋白质上的化学修饰,总结了它们的生物学功能,探讨了修饰之间的相互作用从而阐释修饰组学,希望为DNA、RNA和蛋白质修饰提供一个系统的蓝图,并促进对其功能的研究.     

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%.     

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.     

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.     

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.     

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.     

Highly regioselective Buchwald–Hartwig amination at C-2 of 2,4-dichloropyridine enabling a novel approach to 2,4-bisanilinopyridine (BAPyd) libraries

The highly regioselective Buchwald–Hartwig amination at C-2 of the cheap and readily accessible reagent, 2,4-dichloropyridine with a range of anilines and heterocyclic amines is described. This new methodology is robust and provides a facile access to 4-chloro-N-phenylpyridin-2-amines on 0.25 mol scale. These intermediates undergo a further Buchwald–Hartwig amination at higher temperature to enable rapid exploration of the chemical space at C-4 and to provide a library of 2,4-bisaminopyridines.     

Sulfur-directed metal-free and regiospecific methyl C(sp3)–H imidation of thioanisoles

Regiospecific and direct imidation of the methyl C(sp³)–H bond of thioanisoles is realized under mild and metal-free conditions with N-fluorobis(benzenesulfonyl)imide as an oxidant and nitrogen source. Proposed mechanism suggests that thionium ion intermediates and a Pummerer-type reaction are involved. The imidation has advantages such as high step-economy, excellent functionality tolerance, and regiospecificity, giving structurally diverse imidation products.