新型反相/强阴离子交换混合模式材料用于磷酸化肽富集

建立了新型反相/强阴离子交换混合模式材料(C18/SAX)的磷酸化肽富集方法.考察了流动相组成(乙腈浓度、甲酸浓度、缓冲盐浓度)对酪蛋白(α-Casein)酶解液中磷酸化肽分离选择性的影响.实验结果表明,磷酸化肽在C18/SAX上的保留行为受疏水和离子交换作用力的共同调控,单磷酸化肽先于多磷酸化肽从材料上洗脱出来.随着甲酸浓度增加,磷酸化肽的保留减弱;随着盐浓度增加,磷酸化肽保留变小.采用优化后的流动相,建立以20％ ACN/20 mmol/L NH4Ac作为上样溶液,20％ ACN/0.1％ FA和50％ ACN/100 mmol/L NH4Ac/2％ FA分别作为洗脱液分段洗脱单、多磷酸化肽的方法.以α-Casein和人血清白蛋白(HSA)酶解液的混合溶液(1∶20,n/n)作为模拟样品,实现了单、多磷酸化肽的同时富集和分段洗脱,分别检测到4条单磷酸化肽和14条多磷酸化肽的信号.将本方法用于牛奶中的磷酸化肽检测,共鉴定到4条单磷酸化肽和8条多磷酸化肽信号.结果表明,本富集方法选择性高,有良好的应用前景.     

亲水模式下流动相pH值对磷酸化肽在Click OEG-CD材料上富集选择性的影响

以标准蛋白质α-酪蛋白的酶解液作为研究对象,考察流动相pH值对磷酸化肽在Click OEG-CD材料上富集选择性的影响。首先以磷酸苯二钠作为模型化合物考察流动相pH值对其在Click OEG-CD材料上的保留影响,结果表明当pH值低于磷酸根的pK_a值时,磷酸苯二钠难以电离,与材料的离子交换作用较弱,因而保留也较弱。然后在亲水模式下流动相pH值分别为2, 4, 6时考察Click OEG-CD材料对α-酪蛋白的酶解液中磷酸化肽的富集选择性影响。结果表明,当流动相pH为2时,磷酸化肽不能被材料富集;当pH为4时,磷酸化肽能够被富集,而且洗脱窗口较窄;当pH为6时,磷酸化肽也能够被富集,但是洗脱窗口较宽。因此适合亲水模式下富集磷酸化肽的流动相pH值为4。本研究结果能够为今后将Click OEG-CD材料更好的应用于磷酸化肽富集提供有意义的借鉴。     

基于天冬氨酸的固定化金属离子亲和色谱材料用于磷酸化肽选择性富集

采用点击化学的方法将自然界中的天冬氨酸(aspartic acid)键合到硅球上(命名为Click Asp),并将Fe3+配位到Click Asp上,合成固定金属离子亲和色谱(IMAC)材料(Fe3+-Click Asp);采用红外光谱、X射线电子能谱和扫描电镜等表征证明Fe3+-Click Asp成功合成。将此IMAC材料用于蛋白质酶解液和牛奶中的磷酸化肽的富集,实现了磷酸化肽的高选择性富集。本研究为磷酸化蛋白质组学提供了新材料和新方法。     

合成受体与模型磷酸化肽的相互作用机理

为了研究基于Zn2+-二甲基吡啶胺及胍羰基吡咯基团的配位型受体Zn Dpa G与磷酸化肽的相互作用机制,选取具有不同序列的磷酸化肽作用模型,采用等温滴定微量热法考察了Zn Dpa G与磷酸化肽的结合常数,研究了模型肽中磷酸基团的数量、密度及位置等因素对多肽与受体间结合强度的影响.结果表明,Zn Dpa G受体对双磷酸化肽结合能力显著高于单磷酸化肽,其结合常数可提高10~40倍,2个磷酸基团的距离越近,结合作用越强;而磷酸基团的位置显著影响受体与单磷酸化肽的结合强度.本研究结果为进一步优化磷酸化肽受体结构设计,实现肽与受体间高选择性识别提供了一定的理论依据.     

磷酸化肽富集新方法研究进展

对组成复杂的生物样品中的低丰度磷酸化肽进行预富集,能够消除高丰度非磷酸化肽等干扰组分,从而提高磷酸化肽在质谱分析中的灵敏度,获得更好的检出和鉴定结果.在磷酸化肽富集过程中,对磷酸化肽具有选择性亲和作用的富集材料是实现对磷酸化肽特异高效富集的关键,多种具有不同类型亲和作用的富集材料已在磷酸化肽富集研究中得到了应用;而在材料形貌、富集操作形式、磷酸化肽富集特异性等方面,研究者们也不断在现有磷酸化肽富集材料的基础上进行多样化的改进.本文分别从不同类型亲和作用的磷酸化肽富集材料以及磷酸化肽富集方法改进两方面,对近年来磷酸化肽富集方法的研究进展进行了评述.     

季铵化磁性壳聚糖复合材料对磷酸化肽的富集研究

蛋白质磷酸化是最重要和最普遍的翻译后修饰之一,蛋白质磷酸化的测定对于全面了解生物过程中的磷酸化途径至关重要。质谱技术是分析蛋白质磷酸化的重要手段,但磷酸化肽固有的低丰度、低电离效率以及与非磷酸化肽共存等特性严重影响质谱对其进行直接分析。为解决此问题,需在质谱分析前对磷酸化肽进行选择性富集。本研究制备了一种基于季铵化磁性壳聚糖的复合材料用于磷酸化肽的富集。此磁性材料具有快速的磁响应性、良好的生物相容性、正电性以及廉价易得等优点。采用β-酪蛋白作为模型蛋白质,结果表明此材料对磷酸化肽具有良好的富集选择性。经过富集后,结合基质辅助激光解吸电离飞行时间质谱（MALDI-TOF MS）检测手段,方法的检出限为0.4 fmol。本方法被成功用于脱脂牛奶中磷酸化肽的检测,表明其对复杂样品中磷酸化肽的富集和检测具有良好的应用潜力。     

纳升级电喷雾离子源-四极杆-飞行时间质谱中磷酸化肽的离子抑制作用

目前磷酸化蛋白质组学研究中的主要技术是蛋白质酶解产生的磷酸化肽的质谱检测。但是实际样品中的磷酸化肽(特别是多磷酸化肽)很难被检测到。其原因普遍认为是由于质谱检测时,非磷酸化肽抑制磷酸化肽。但也有认为非磷酸化肽对磷酸化肽没有抑制作用。另外磷酸化肽之间是否存在离子抑制作用还没有报道。本文采用相同氨基酸序列的标准磷酸化肽和非磷酸化肽,将其单独和混合进行质谱检测,通过对比混合前后磷酸化肽的信号强度,证明了非磷酸化肽对磷酸化肽有离子抑制作用;单磷酸化肽对二磷酸化肽有一定的抑制作用,但不太显著;单磷酸化肽对三磷酸化肽、二磷酸化肽对三磷酸化肽均有显著的离子抑制作用。该研究为今后单磷酸化肽和多磷酸化肽的分段富集和检测提供了有力的证明。     

介孔氧化铁材料快速、高效富集分离磷酸化肽段和蛋白的新方法研究

以0.1μmol/Lβ-casein磷酸化蛋白酶解液为对象,利用在酸性条件下对PO43-能够特异性吸附的氧化铁材料为新载体,对介孔氧化铁材料富集分离磷酸化肽段的孵育液酸含量、孵育液有机溶剂含量和洗脱液选择的条件进行了优化,结果表明:室温条件下,在含有0.1%乙酸和30%乙腈的孵育液中孵育5min后,经1mol/LNH3.H2O溶液的洗脱,介孔氧化铁可有效地将磷酸化肽段从蛋白酶解液中富集分离。本方法也可以选择性地提取α-casein磷酸化蛋白,实现了简单、快速、高效的磷酸化肽段和蛋白的富集分离。同时,通过MALDI-TOF串级质谱分析,成功地完成了在优化条件下分离出的磷酸化肽段磷酸位点的鉴定。     

微柱液相色谱-电喷雾串联质谱检测多磷酸化肽位点

基于碱性磷酸酶的去磷酸化作用,发展了一种可改善多磷酸化肽电喷雾质谱检测效果的技术。将β-酪蛋白酶解产物用TiO2柱富集后,用碱性磷酸酶进行处理,并经微柱液相色谱分离后采用串联质谱进行鉴定。通过谱图中存在相对分子质量与根据氨基酸序列预计的单磷酸化肽相差80 的色谱峰,可以证实样品中含有单磷酸化肽。此外,经碱性磷酸酶处理后的样品的色谱峰数目的增加,说明样品中可能存在多磷酸化肽段。通过控制去磷酸化反应的程度,使四磷酸化肽的部分磷酸基团被去除,从而可以推断其中3 个磷酸化位点可能处于氨基酸残基序列的第17、18和19位。     

介孔氧化钛对多磷酸化肽段的高灵敏度分析

蛋白质的磷酸化修饰广泛存在于细胞生命活动进程中,在细胞的分化、繁殖、代谢及信号转导等方面均发挥着重要作用.MALDI-TOF-MS技术因其高灵敏度等优点,已成为蛋白质研究的重要分析工具之一.由于磷酸化蛋白的天然丰度和离子化效率较低、检测信号被抑制等缺点,因此需要发展新的分析方法以提高其分析灵敏度和选择性.本文建立了基于介孔氧化钛的多磷酸化肽段高效分析方法,同时利用了TiO2对磷酸化肽的选择性吸附作用和介孔材料特殊空间结构所形成的对多磷酸肽的动力学及热力学吸附效应,结合MALDI-TOF-MS技术,成功地实现了对混合溶液中多磷酸化肽的选择性富集和高灵敏度分析鉴定,与其他方法相比,分析性能得到明显的提高,可实现对低量磷酸化肽段的识别与检测.     

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%.     

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.     

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.     

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.     

Chemistry of heterocyclic compounds at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences, over 50 years (Review)

The review contains a concise historical account and information on the most significant researches undertaken by the staff at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences on the Chemistry of Heterocyclic Compounds. Dedicated to Academician of the Russian Academy of Sciences B. A. Trofimov on his 70th jubilee. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1443–1502, October, 2008.     

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.