基于多肽自组装的人工金属酶

模拟酶,又称人工酶,是在分子水平上模拟天然酶活性部位的形状、大小及其微环境等结构特征的分子或分子聚集体。随着纳米科学和超分子技术的发展,构筑具有生物催化活性的超分子模拟酶已经成为科学研究和应用开发领域的热点。肽组装金属酶是以多肽分子为基本单元,在非共价作用力协同作用下形成的超分子组装体。相比其他功能性材料,肽人工金属酶的结构及生物化学性质更接近天然酶,其分子本身更利于修饰改造,且生物相容性和功能性较好,使其在模拟酶方面具有独特优势。本文总结了近年来通过多肽自组装构建人工金属酶的研究进展,重点综述了多肽组装模式、组装体微观结构、超分子结构、金属活性中心微环境以及pH值对模拟酶催化活性的影响。增加自组装微结构的稳定性、增加催化活性以及扩大由人工酶催化的反应类型是肽人工金属酶研究中的主要挑战。构筑更加稳定的肽自组装纳米结构及更加精确的活性中心以模拟天然酶的结构和活性中心是正确的策略。     

催化水解反应的肽基模拟酶的活性来源、催化机理及应用

肽基材料由于其与蛋白质高度相似和结构可控等优势,是构建人工模拟酶的一种理想材料;此外,小肽中氨基酸排列的多样性、序列的自组装特性、纳米结构稳定性、结构简单易于设计、良好生物相容性等优势,使得构建具有高效催化活性的肽基模拟酶具有非常好的应用前景。利用肽基材料通过理性设计活性位点来构建模拟酶具有多方面优势:(1) 氨基酸序列可以直接从天然酶中的活性位点获得,保留酶的功能,但降低了酶固有的复杂性;(2) 肽序列中可以嵌入各种具有特定结构及功能的活性位点,便于对模拟酶进行人工理性设计;(3) 肽具有良好的生物相容性,可以在温和条件下催化反应进行。根据催化降解化学键的不同,可将肽基水解模拟酶分为以下几种:催化酯键降解的肽基模拟酶、催化肽键降解肽基模拟酶、催化糖苷键水解的肽基模拟酶。本文主要分析了具有水解酶活性的肽基模拟酶的活性来源、构建方法及微观结构、催化反应类型、催化影响因素、活性改善方法、作用机理及未来潜在应用等;以期为构建具有高效水解催化活性的模拟酶提供借鉴,推进肽基水解模拟酶的研究发展及实际应用。     

肽基超分子胶体

肽基超分子胶体是基于肽分子间超分子作用,自发形成且具有有序分子排布及规整结构,兼具传统胶体及超分子特性的组装体系。利用超分子弱相互作用构筑功能性胶体,不仅是人们对生命组装进程深入理解的有效手段,也是实现优异的超分子材料的重要途径。肽分子具有组成明确、性能可调、生物安全性高及可降解等优势,是超分子化学、胶体与界面化学领域重要的组装基元。基于肽的超分子自组装,能够实现多尺度、多功能的生物胶体的构筑,被广泛应用于医药、催化、能源等领域。如何通过对肽序列的设计及分子间作用力的调控,实现对胶体结构和功能的精确控制,是近年来研究的重要课题之一。从分子尺度研究和揭示超分子胶体的组装过程及物理化学机制,探究胶体结构与功能的关系,是实现超分子结构和功能化的重要内容。本文基于"分子间作用的调控"及"结构与功能的关系"两个基本科学问题,系统地综述了肽基超分子胶体的组装机制、结构与功能,以及研究现状。     

超分子凝胶的手性功能应用:手性分子识别与不对称催化

超分子凝胶通过形成三维空间网络结构将溶剂液体相固定化,是一类重要的软物质材料。由于超分子凝胶能快速形成,自组装形成的纳米结构均一、可调,且可大规模制备,因此成为超分子化学、纳米技术以及材料科学研究的重要研究方向之一,并在诸多领域得到广泛的功能研究和应用拓展,如在材料模板、光电开关、药物释放、分子识别和超分子催化等方面已有大量研究报道。由于超分子凝胶具有固-液相可逆转变、可控组装等特性,成为了超分子手性和分子手性研究的重要载体。近年来超分子凝胶在超分子手性催化、手性分子识别等方面取得了一系列重要突破,为超分子凝胶功能应用开辟了新的空间,为手性科学研究提供了新的手段和方法。     

DNA-多肽复合分子的设计、组装与应用

DNA-多肽复合分子作为一类新型的自组装分子受到研究人员的广泛关注。DNA分子具有可编程性、高特异性、功能多样等优点,多肽分子是一类重要的生物小分子,能够通过分子自组装形成具有不同结构的纳米材料,因此,将二者通过共价交联,可以获得具有多级自组装行为的DNA-多肽复合分子,能够实现两类重要生物分子功能的集成优化,合成具有不同结构与功能的超分子自组装材料。此外,通过酶催化、DNA杂化、DNA链置换反应等,还可实现对多肽-DNA复合分子自组装行为的动态调控,进而模拟生命系统中复杂动态的自组装结构,强化相关材料在生物、化学、材料等领域的应用。本文讨论了DNA-多肽复合分子的设计、组装与应用方面的最新进展,最后基于目前DNA-多肽复合分子存在的一些问题对DNA-多肽复合分子的研究做了展望。     

苯丙氨酸二肽类分子自组装:分子设计、结构调控与材料应用

近年来,苯丙氨酸二肽类分子的自组装研究受到了广泛关注,已成为超分子化学、生物材料科学研究的前沿领域之一。苯丙氨酸二肽类纳米组装体因具有结构多样、易功能化以及良好的生物相容性等优点,在纳米制造、组织修复等方面展示出巨大的应用潜力。本文从分子设计、组装结构调控与材料应用三个层次系统综述了苯丙氨酸二肽类分子自组装的研究进展。首先总结了苯丙氨酸二肽类分子的修饰改性,包括乙酰基、芳香环、氨基酸、短肽等基团。然后,重点介绍了苯丙氨酸二肽类分子自组装的调控策略和方法,如溶剂、界面、气相、多组分共组装和酶催化组装。最后,介绍了苯丙氨酸二肽类自组装材料在纳米材料合成、传感检测、药物传递及组织修复等方面的应用现状,并分析了该领域今后的发展方向。     

超分子聚合物凝胶

作为非常重要的软物质材料,超分子聚合物凝胶代表了一个全新的概念和更复杂的凝胶体系.这种新型的超分子体系的构建,是基于多种非共价相互作用协同的多层次组装.即小分子构筑基元首先组装成为超分子聚合物,而这些非共价聚合物的多层次组装形成凝胶的纳米结构.超分子聚合物凝胶无论是在结构上,还是在性能上都具有很多崭新的特点.因此,尽管有关超分子聚合物凝胶的研究开展的时间还很短,这一体系所表现出的独特性以及巨大潜力已经引起科学家们越来越广泛的关注.本文简要综述了这一领域的最新进展.主要论述基于多种非共价相互作用的超分子聚合物凝胶的构建以及对其力学性能的调控.     

超分子凝胶:结构多样性与超分子手性

超分子凝胶作为一种重要的软物质材料,在构建多重刺激响应性、光电功能,以及生物相容材料等功能软物质方面表现出了独特的优越性。超分子凝胶在形成过程中往往得到比较均一的纳米结构,且具有结构多样性;而另一方面,超分子凝胶的构筑单元大部分是手性分子,超分子凝胶也是实现手性在超分子层次/纳米层次表达的重要途径,尤其是手性传递、手性放大、不对称催化方面,同时超分子凝胶也是构筑手性纳米结构的重要手段。本文主要对超分子凝胶形成中的纳米结构以及形貌的多样性和超分子手性进行介绍,并展望该领域未来的发展方向。     

环糊精在金属酶模拟中的应用

非共价作用（如氢键、静电和疏水作用）普遍存在于天然金属酶中,对酶活化或底物催化过程有重要的协同作用.近年来基于超分子化学理论的金属酶模拟研究不断向酶的活性中心亚稳态和次层结构的生物功能模拟方向发展.本文将根据报道的文献并结合本课题组的研究工作,对环糊精（一种重要的超分子主体）构建金属酶模型的研究进行综述.     

基于天然产物骨架的有机凝胶

天然产物结构复杂,生理活性独特,常被用作先导化合物,经过结构修饰和改造,发展为具有重要药用价值的化合物,在保障人类健康方面发挥重要的作用.近年来,具有独特立体结构、多修饰位点、良好生物相容性和生物活性的天然产物作为构筑单元,已应用到基于分子自组装的有机功能材料研究领域中.介绍以天然甾体、三萜、肽、糖等为结构骨架,设计合成的功能分子在有机凝胶方面的研究现状及其潜在的应用.     

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%.     

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.     

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.     

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.     

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.