N-磷酰化肽酯及小肽与氨基酸相互作用的ESI-MS研究

采用ESI-MS研究了一系列结构具有可比性的N-二异丙氧基磷酰化肽酯及小肽同20种蛋白氨基酸及3种D型氨基酸(D-Ala、D-Ser、D-Phe)的非共价相互作用.结果表明,可形成π-π共轭体系的芳香环,可显著增强磷酰化肽酯及小肽与氨基酸的相互作用力,π-π堆积力是首要的非共价相互作用力;可形成氢键的极性基团有利于形成复合物,但能否形成氢键还要受到分子柔顺性的影响;另外,分子大小、空间位阻对复合物的形成也有影响;而氨基酸的手性对它们的相互作用在质谱条件下没有表现出影响.     

ESI质谱法对黄酮-7-磷酰化氨基酸酯与溶菌酶相互作用的研究

采用电喷雾(ESI)质谱技术,研究了4种黄酮-7-磷酰化氨基酸酯与溶菌酶的弱相互作用,实验结果表明4种化合物均能与溶菌酶形成非共价复合物,在相同条件下,未检测到黄酮与溶菌酶形成的非共价复合物,说明在黄酮分子中引入N-磷酰化氨基酸,能改变黄酮的分子极性,从而使其与生物大分子之间的相互作用情况发生变化;通过改变锥孔电压,分别对4种黄酮-7-磷酰化氨基酸酯-溶菌酶复合物的耐压能力进行检测.结果显示,黄酮-7-磷酰化氨基酸酯b与溶菌酶形成的复合物最稳定,它们之间存在最强的弱相互作用.     

N-磷酰化多巴胺与溶菌酶相互作用的ESI-MS研究

采用电喷雾离子肼-质谱(ESI-MS)研究了一系列结构具有可比性的N-磷酰化多巴胺与溶菌酶的非共价相互作用, 比较了磷上不同取代基对相互作用的影响. 结果表明, 磷上的烷氧取代基上烷基碳原子的个数及排列顺序对二者相互作用有较大影响; 取代基上碳链越长, 溶液中溶菌酶的构象越趋于收缩, 二者之间越容易形成带低电荷和高质核比的复合物, 且其稳定性也随着取代基的增长而增强; 当取代基碳原子数相同时, 直链取代的磷酰化多巴胺与溶菌酶形成的复合物比支链取代的底物与溶菌酶形成的复合物稳定.     

二芳基三嗪类HIV-1逆转录酶抑制剂的分子对接及3D-QSAR研究

对40个二芳基三嗪类HIV-1逆转录酶抑制剂进行了分子对接研究,结果表明,2个疏水性芳香取代基团与结合口袋底部形成的疏水和范德华相互作用、三嗪环母核及其R4取代基与结合位点产生的氢键和静电作用以及R4取代基与袋口形成的空间位阻效应是影响该系列化合物活性的重要因素.根据对接优势构象进行分子叠合和比较分子相似性指数分析(C...     

环十二肽溶液构象的二维核磁共振研究

利用二维核磁共振方法及距离几何计算研究了在片段组装法全新蛋白质合成中用作底座分子的环十二肽的溶液构象. 研究结果表明在环十二肽分子主链中包含四个转角结构,四个赖氨酸侧链均位于环的同一侧.环肽的构象为以环肽为模板组装四螺旋束分子提供了有利的条件     

聚肽分子链构象转变研究

聚肽分子链在一定的条件下可发生右旋分子链构象与左旋分子链构象间的构象转变 .文中提出了一个有关这一现象的统计理论解释 ,理论包含了两个重要的参数γ、ρ .γ与右旋和左旋分子链构象间能量差别有关 ;ρ与在左旋分子链段中启始一个右旋构象的结构单元所需能量有关 .进一步考虑了体系中酸分子存在对构象转变的影响 ,以解释新近发现的聚肽左、右旋多重分子链构象转变现象 .此外 ,运用核磁共振 (NMR)手段还对这一现象做了进一步的研究 .通过与实验结果和文献中报告的数据比较 ,证明这一理论可以很好地解释聚肽分子链中发生的左、右旋分子链构象转变     

磷酰化对丙氨酸与溶菌酶相互作用的影响

在电喷雾离子阱质谱图中发现丙氨酸不能和溶菌酶形成二聚体, 而磷酰化丙氨酸(DIPP-Ala)能和溶菌酶形成二聚体. 进一步研究发现丙氨酸及其他氨基酸磷酰化后, 自身形成二聚能力大大增强. 在Silicon Graplics图形工作站上采用SYBYL 6.8软件, 利用Tripos力场和分子力学方法研究了DIPP-Ala最低能量构象, 并用分子对接(DOCK)研究了二聚体的形成. 结果说明磷氧双键的存在增强了分子间的相互作用.     

特殊氢方法预测丙氨酸-α-四肽构象稳定性

使用B3LYP/6-31G*方法优化得到了丙氨酸-α-四肽分子的48个稳定构象.定义了丙氨酸-α-多肽中的特殊氢原子,对构象中与特殊氢原子有关的主要非键相互作用进行分析,提出了使用与特殊氢原子有关的非键相互作用来预测多肽构象的相对稳定性,并将之称为特殊氢方法.基于丙氨酸-α-二肽分子的5个构象和三肽分子的7个构象,确定了特殊氢方法中的与特殊氢原子有关的非键相互作用参数.利用特殊氢方法预测丙氨酸-α-四肽分子的48个构象的相对稳定性,与B3LYP/6-31G*方法的相对能量比较,得到了满意的结果.特殊氢方法得到的相对能量(Y)和B3LYP/6-31G*方法得到的相对能量(X)的线性相关方程为Y=0.9296X 2.2041,相关系数R=0.9532,标准偏差为3.0kJ/mol,偏差绝对值≤4.18kJ/mol的构象占87.5%.     

多肽酰肼连接法合成环四肽

环四肽在药物研发中具有重要的潜在应用价值, 然而目前尚缺乏高效率合成环四肽的方法. 我们发展了以N端为半胱氨酸的四肽酰肼为原料的分子内环化方法, 合成了全L型氨基酸组成的环四肽. 该方法通过形成13元环的内硫酯中间体, 再经过S-to-N酰基迁移形成酰胺键, 最后通过脱硫反应, 得到目标环四肽分子.     

订书肽的合成与应用

许多重要的生物过程的调节都通过蛋白-蛋白相互作用来实现的。一般,蛋白-蛋白作用的界面太大而不能被小分子药物选择性靶向,因此小分子药物很难高效特异性地阻断该类型的相互作用。此外,由于蛋白质药物很难透过细胞膜,它们也不能直接靶向细胞内的相互作用。由于当前药物分子的限制,发展下一代既能进入细胞膜又能特异性靶向蛋白-蛋白相互作用的分子成为新的研究热点。为了克服上述药物分子的缺点,Verdine等发展了一种全碳支架的具有α-螺旋结构的新型多肽,这种多肽被称作订书肽（stapled peptides）。相比于天然多肽,订书肽有更高的酶解稳定性并且可以进入细胞膜,从而提高了它的药理性能。本文将从订书肽的化学合成、生物物理性能的表征和其在癌症和HIV治疗、信号通路的调节和肿瘤激活蛋白的抑制方面的生物应用详细介绍订书肽的最新进展。     

Characterization of electrospray ionization mass spectrometry for N-diisopropyloxyphosphoryl dipeptide methyl esters

A systematic study of the fragmentation pattern of N-diisopropyloxyphosphoryl (DIPP) dipeptide methyl esters in an electrospray ionization (ESI) tandem mass spectrometry (MS/MS) was presented. A combination of accurate mass measurement and tandem mass spectrometry had been used to characterize the major fragment ions observed in the ESI mass spectrum. It was found that the alkali metal ions acted as a fixed charge site and expelled the DIPP group after transferring a proton to the amide nitrogen. For all the N-phosphoryl dipeptide methyl esters, under the activation of a metal ion, the rearrangement product ion at m/z 163 was observed and confirmed to be the sodium adduct of phosphoric acid mono-isopropyl esters (PAIE), via a specific five-membered penta-co-ordinated phosphorus intermediate. However, no rearrangement ion was observed when a beta-amino acid was at the N-terminal. This could be used to develop a novel method for differentiating isomeric compounds when either alpha- or beta-amino acid are at the N-terminus of peptides. From the [M+Na]+ ESI-MS/MS spectra of N-phosphoryl dipeptide methyl esters (DIPP Xaa1 Xaa2 OMe), the peaks corresponding to the [M+Na Xaa1 C3H6]+ were observed and explained. The [M+Na]+ ESI-MS/MS spectra of N-phosphoryl dipeptide methyl esters with Phe located in the C-terminal, such as DIPPValPheOMe, DIPPLeuPheOMe, DIPPIlePheOMe, DIPPAlaPheOMe and DIPPPhePheOMe, had characteristic fragmentation. Two unusual gas-phase intramolecular rearrangement mechanisms were first proposed for this fragmentation. These rearrangements were not observed in dipeptide methyl ester analogs which did not contain the DIPP at the N-terminal, suggesting that this moiety was critical for the rearrangement.     

Derivatizat Ion of Primary Aromatic Amines with Fluorescamine

Abstract

Fluorescamine forms stable, fluorescent derivatives with sterically-unhindered primary aromatic amines in both aqueous (borate buffer, pH 9/acetonitrile) and nonaqueous (pyridine/-acetonitrile) media. Aromatic amines with a substituent such as a methyl group or an aromatic ring ortho to the amine functionality either derivatized poorly or not at all because of steric hindrance.     

Mono-carboxylated diaminedichloridoplatinum(IV) complexes--selective synthesis, characterization, and cytotoxicity

(OC-6-43)-Dichlorido(N,N-dimethyl-ethane-1,2-diamine)dihydroxidoplatinum(IV) could selectively be mono-carboxylated with succinic anhydride based on the steric hindrance caused by the two methyl groups of the equatorial ligand. Subsequent esterification of the uncoordinated carboxylic acid with alcohols of different lengths (methanol, butanol, hexanol and octanol) afforded the corresponding esters. The synthesized complexes were characterized in detail by elemental analysis, ESI-MS, multinuclear ((1)H, (13)C, (15)N and (195)Pt) NMR spectroscopy and in two cases by X-ray crystallography. Cytotoxicity of novel platinum(IV) compounds was investigated in four human cancer cell lines (CH1, A549, SW480 and SK-OV-3). Remarkably, the most lipophilic complexes showed IC(50) values down to the low micromolar or even nanomolar range.     

气相色谱研究杯[4]芳烃衍生物

选取两种不同结构的怀「４」芳烃做固定相，研究了烃基取代苯，不同数目的甲基取代苯，稠环芳烃和醇系列化合物的保留值变化规律；讨论了杯「４」芳烃固定相与溶质分子间的弥散力作用，氢键作用及空间适应性；指出杯「４」芳烃对芳香烃等良好选择性；对乙腈和甲醇等小分子似有包结。     

Etude en RMN du 13C des Effets de Substituant sur les Déplacements Chimiques du Carbone dans les Méthyl Tétrahydrofurannes

Carbon-13 nuclear magnetic resonance spectra have been recorded and interpreted for some methyltetrahydrofurans. The effects of a methyl substituent on the ring carbon atoms are discussed in terms of steric hindrance and conformational equilibrium.     

Preparation and characterization of six calixarene bonded stationary phases for high performance liquid chromatography

Six calixarene bonded silica gel stationary phases were prepared and characterized by elemental analysis, infrared spectroscopy and thermal analysis. Their chromatographic performance was investigated by using PAHs, aromatic positional isomers and E- and Z-ethyl 3-(4-acetylphenyl) acrylate isomers as probes. Separation mechanism based on the different interactions between calixarenes and analytes were discussed. The chromatographic behaviors of those analytes on the calixarene columns were influenced by the supramolecular interaction including pi-pi interaction, space steric hindrance and hydrogen bonding interaction between calixarenes and analytes. Notably, the presence of polar groups (-OH, -NO(2) and -NH(2)) in the aromatic isomers could improve their separation selectivity on calixarene phase columns. The results from quantum chemistry calculation using DFT-B3LYP/STO-3G* base group were consistent with the retention behaviors of PHAs on calix[4]arene column.     

Spectrophotometric study of the reaction between cobalt(II)-dipeptide complexes and molecular oxygen

Summary The influence of pH and ligand structure on the reaction of cobalt(II) complexes with various dipeptides and molecular oxygen was examined. The minimum pH value required for the formation of dioxygen adducts was found to be about 6.5. This value should be related to amidic deprotonation of dipeptides, which seems to occur in the examined systems at particularly low values. The location and steric hindrance of the side chains of the dipeptides have a strong influence on the reaction rate. The presence of a substituent group on the N-terminal amino acid promotes oxygen coordination, while, when the substituent group is on the C-terminal residual, a decrease of reaction rate is observed.A stabilizing effect of the aromatic ring on the dioxygen adducts is found only when the substituent is in the C-terminal position, and seems to be independent of the presence of additional coordinating groups.Some information regarding the mechanism of the irreversible decomposition of the cobalt(II) complexes has been obtained by studying the effect of pH and ligand structure on the reaction rate.Work supported by National Research Council of Italy.     

分子量及酰基供体对酶促魔芋葡甘聚糖酰化反应的影响

研究了在有机介质叔丁醇中魔芋葡甘聚糖(KGM)的分子量及酰基供体对固定化脂肪酶Novozym 435催化KGM乙酰化反应的影响.KGM的分子量对酶促其酰化反应的活性及产物取代度有显著影响.随着KGM分子量的增大,酶催化反应的速率逐渐下降,产物的取代度逐渐减小.KGM分子量对该反应的影响与不同分子量KGM的溶解度、体系粘度、空间位阻及颗粒形态等因素有关.以不同链长的脂肪酸乙烯酯为酰基供体时,随着酰基供体中脂肪酸碳链的增长,酶促KGM酰化反应速率逐渐下降,产物的取代度逐渐减小,且该酰化反应具有高度的区域选择性,反应均发生在C6-OH上.