荧光法研究不同离子对溶菌酶的猝灭作用

本文利用荧光法,在生理pH(7.37±0.02)条件下,分别测定了Fe3+、Cu2+、Ni2+、Co2+、NO2-、I-、盐酸胍对溶菌酶的猝灭作用。用荧光猝灭法求得不同猝灭剂对溶菌酶的猝灭常数KSV、生成常数KA、离解常数KD、结合位点数n和热力学参数ΔrGmΘ、ΔrHmΘ、ΔrSmΘ。据此判断了体系中猝灭剂对溶菌酶的作用机理。I-对溶菌酶的猝灭是动态猝灭,而Fe3+、Cu2+、NO2-Ni2+、Co2+及盐酸胍对溶菌酶是静态猝灭;Fe3+、Cu2+、Ni2+、Co2+与溶菌酶之间的作用力主要为氢键、范德华力;NO2-与溶菌酶间的作用力主要为静电作用力;I-与溶菌酶之间的作用力主要为疏水作用力。在分子水平上理解这些外源性化合物与溶菌酶的作用机理具有及其重要意义。     

药物青蒿素与溶菌酶相互作用研究

应用荧光光谱、紫外-可见光谱法研究了青蒿素与溶菌酶的相互作用,发现青蒿素对溶菌酶荧光有猝灭作用。以Lineweaver-Burk双倒数方程和能量传递原理分别计算了二者反应的结合常数(K25℃=646.4L/mol,K35℃=518.8L/mol)和作用距离(r=3.08nm)。实验表明,随着温度升高,溶菌酶与青蒿素的猝灭曲线斜率降低,证明了二者的相互结合作用为单一的静态猝灭过程,其作用机制属能量转移机制。通过测定热力学参数,判断了青蒿素和溶菌酶之间的作用力类型,青蒿素与溶菌酶以疏水作用力相结合,导致溶菌酶内源荧光的静态猝灭。通过青蒿素与溶菌酶的结合反应,探讨了药物青蒿素在生物体内与蛋白酶的相互作用机理。     

光谱法与分子模拟技术研究丽春红2R与牛血清蛋白的相互作用

采用荧光光谱、同步荧光光谱、紫外-可见吸收光谱及分子模拟技术研究了模拟生理条件下丽春红2R(P2R)与牛血清白蛋白(BSA)的相互作用。实验结果表明,P2R-BSA体系的荧光猝灭机制为内源荧光猝灭,猝灭原因为静态猝灭和非辐射能量转移;计算了不同温度下体系的结合常数Ka及结合位点数n;根据热力学参数推断出作用力类型;求出室温下荧光给体-受体间的结合距离;同步荧光法证实丽春红2R对BSA构象未产生影响;分子模拟研究结果表明二者间的主要作用力为氢键和疏水作用力。     

3种苯丙胺类药物与溶菌酶的作用机制及构效关系研究

在模拟人体生理条件下,采用荧光光谱法研究了3种不同结构的苯丙胺类药物(麻黄碱、伪麻黄碱和甲基麻黄碱)与溶菌酶之间的相互作用,计算了其结合常数、结合位点数和热力学参数,并探讨了3种药物对溶菌酶构象的影响.研究发现,三者可对溶菌酶内源性荧光产生强烈的猝灭作用,其猝灭过程均为静态猝灭.麻黄碱、伪麻黄碱和甲基麻黄碱与溶菌酶均形...     

新洁尔灭与过氧化氢酶的微观作用机理

模拟生理条件下,利用多种光谱技术和酶活性测定法研究了新洁尔灭与过氧化氢酶的相互作用过程,探讨了二者的结合特性,过氧化氢酶空间结构和酶活性的变化.结果表明新洁尔灭对过氧化氢酶无荧光猝灭作用,其使过氧化氢酶骨架结构变松散,部分氨基酸残基微环境和蛋白二级结构发生改变,说明新洁尔灭对过氧化氢酶活性具有显著的抑制作用.从分子水平上证明了新洁尔灭可改变过氧化氢酶的结构和功能.     

光谱法研究埃洛石纳米管与溶菌酶间的相互作用

以溶菌酶作为模型蛋白,主要利用光谱法研究了埃洛石纳米管与溶菌酶之间的相互作用。荧光光谱结果表明向溶菌酶体系中加入埃洛石纳米管会出现荧光猝灭现象,猝灭机理符合静态猝灭规律。共振光散射强度的增加可能与埃洛石纳米管-溶菌酶复合物的形成而导致的分子尺寸的增加有关,这与紫外-可见吸收光谱的变化和静态猝灭机理相一致。同步荧光光谱分析表明两者之间的相互作用可能发生在色氨酸所处位置附近,作用过程使溶菌酶的二级结构发生变化,分子链错误折叠,加入浓度为100mg/L和200mg/L的埃洛石纳米管时,通过圆二色谱数据计算出分别导致α-螺旋的含量降低3.28%和6.89%。     

Cu2＋和Fe3＋与明胶的相互作用

利用荧光猝灭法, 研究了不同温度、酸度下, Cu2＋和Fe3＋与明胶的相互作用.计算了猝灭常数和结合常数.紫外光谱和显微红外光谱的测定结果表明, Cu2＋、Fe3＋与明胶分子中的酰胺键发生了作用.探讨了猝灭机理.计算出的热力学函数表明,在Cu2＋、Fe3＋与明胶的相互作用过程中熵变起主要的作用.     

碲化镉量子点的制备及与岩白菜素相互作用的研究

以巯基丙酸为稳定剂,采用一步水合法制备水溶性功能化CdTe量子点。并通过高分辨透射电子显微镜(HRTEM)、X射线衍射仪(XRD)、傅里叶红外变换光谱(FT-IR)、荧光分光光度计(MF)对量子点的光学性能和结构进行表征。应用荧光猝灭法,研究溶液状态下岩白菜素和CdTe量子点的相互作用及时间、温度等诸多因素对相互作用的影响,并在此基础上对二者相互作用的机理进行了研究分析。在溶液状态下,岩白菜素对CdTe量子点有明显的猝灭作用,Stern-Volumer猝灭常数K_(SV)值在10~5L/mol数量级,其二者的猝灭机理为静态猝灭,热力学结果显示其二者的猝灭过程是自发进行的。     

二价铅离子与牛血清白蛋白相互作用的荧光光谱研究

用荧光法研究了二价铅离子与牛血清白蛋白的相互作用,测定了不同条件下pb2+与BSA作用的荧光光谱,并通过热力学计算探讨了二者的作用方式、BSA荧光的猝灭机理、Pb2+与BSA之间的结合常数及结合位点.结果表明,Pb2+对BSA的荧光猝灭属于静态猝灭,pb2+通过疏水作用力进入BSA的疏水腔与之发生相互作用,反应的△G=...     

荧光法研究金属离子对橙皮素与牛血清白蛋白相互作用的影响

采用荧光光谱和三维荧光光谱法研究了橙皮素(HSP)与牛血清白蛋白(BSA)之间的相互作用,并考察了共存金属离子Cu2+,Zn2+对二者相互作用的影响。实验结果表明,HSP对BSA的内源性荧光具有猝灭作用,猝灭类型为静态猝灭,作用力类型是氢键和范德华力,Cu2+,Zn2+的加入未改变HSP对BSA的猝灭类型和作用力类型。通过比较猝灭常数、结合常数、结合位点数、猝灭效率和三维荧光光谱图变化,推知Cu2+,Zn2+能与BSA产生结合作用,使其成为受制状态下的刚性肽链,从而影响HSP进入BSA疏水腔,减弱了HSP与BSA的结合能力,表现为与HSP存在竞争作用。     

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.     

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.     

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.