生物无机化学范式的转变:硅质海绵动物中二氧化硅的酶促缩聚反应(英文)

硅蛋白的发现导致了生物无机化学范式的转变,因为它是第一个可以催化无机单体合成无机聚合物分子的酶。分子生物学,生物化学和细胞生物学数据证实,两种硅质海绵动物,包括寻常海绵和六放海绵,它们的骨针都是由硅蛋白/酶催化合成的。这种酶不仅存在于硅质海绵骨针内部,而且也存在于硅质海绵骨针表面。在硅质海绵骨针生长过程中,它催化生物二氧化硅的合成而构建硅薄层,一层层的硅薄层逐步沉积从而形成硅质海绵骨针。寻常海绵动物Suberites domuncula体外实验获得的硅蛋白活性数据(催化生物二氧化硅的形成)反映了体内骨针生长所需的生物二氧化硅量。本文最后总结了在寻常海绵动物骨针生长和成熟过程中出现的生物熔合现象,即内部的硅薄层"烧结"在一起形成致密的硅棒。强壮的和坚硬的生物二氧化硅骨架的形成需要经历一个硬化过程,这个过程由海绵动物排水通道表面的细胞膜控制,排除生物二氧化硅缩聚反应过程中释放出的水分而使材料固化。     

含二氧化硅组份Janus纳米粒子的制备方法和应用研究进展

Janus纳米粒子的非对称结构赋予其在空间结构和物理化学性质的各向异性,在半导体、催化、分散介质、生物医药等领域表现出优于普通纳米材料特性,是近年来纳米材料的研究热点.近些年来的研究报道多集中在含二氧化硅组份的Janus纳米粒子上,按其化学组成主要分为无机物-二氧化硅和聚合物-二氧化硅两大类.按此分类分析比较了Janus纳米粒子的制备方法,并介绍了其在药物输送、表面活性剂和催化等领域的应用现状.     

树枝状介孔二氧化硅的研究进展

介绍了树枝状介孔二氧化硅的三种合成方法,分别是微乳液合成、两相界面合成及球形胶束自组装合成法,为精确调节树枝状介孔二氧化硅的结构,探讨了不同方法可能的形成机理.由于球形胶束自组装合成法的绿色经济,重点讨论了球形胶束自组装合成法的发展及形成机理.介绍了树枝状介孔二氧化硅纳米材料在催化和生物医学方面的应用效果,并对树枝状介...     

Janus纳米材料的制备及结构调控

用3-(甲基丙烯酰氧)丙基三甲氧基硅烷(MPS)、 氨丙基三乙氧硅烷(APTES)和正硅酸乙酯(TEOS)溶胀聚苯乙烯中空微球的壳层, 在壳层表面通过溶胶-凝胶过程, 使亲油和亲水基团通过自组装作用分别朝向聚苯乙烯基体和水相, 形成Janus结构. 用良溶剂N,N-二甲基甲酰胺(DMF)溶解除去聚苯乙烯, 得到二氧化硅基复合Janus纳米材料. 改变反应体系pH值和单体用量等可以调控Janus纳米材料微结构, 得到Janus中空球和纳米片.     

固定化金属离子亲和发光二氧化硅纳米粒子的制备及其用于磷酸化蛋白免疫印迹标记

发展了一种能够识别磷酸化蛋白的固定化金属离子亲和发光二氧化硅纳米粒子用于免疫印迹(Western Blot)磷酸化蛋白的标记.首先通过反相微乳液St?ber方法合成了掺杂异硫氰酸荧光素硅烷化衍生物的发光二氧化硅(FITC@SiO2)球形纳米粒子,粒子平均粒径为60 nm.然后通过共聚反应在FITC@SiO2纳米粒子表面...     

静电力驱动蛋白质在疏水蛋白表面的吸附

疏水蛋白是丝状真菌产生的一种外泌蛋白质, 它们可以在不同表面形成双亲性蛋白膜. 疏水蛋白也是一种优良的蛋白质固定化基质, 然而蛋白质在疏水蛋白表面吸附的驱动机制却是未知的. 本文系统研究了不同pH和离子浓度下蛋白质在疏水蛋白表面的吸附. 首先, 用石英晶体微天平技术研究了不同pH和离子浓度下, Ⅰ型疏水蛋白HGFI和Ⅱ型疏水蛋白HFBI在聚苯乙烯表面的吸附. 结果发现, pH和离子强度对HGFI在聚苯乙烯表面的吸附影响较大, 对HFBI的吸附影响与HGFI相比则较小; HGFI在聚苯乙烯表面主要形成的是弹性膜, 而HFBI在聚苯乙烯表面主要形成的是刚性膜. 随后又研究了不同pH和离子浓度下牛血清白蛋白(BSA)和亲和素(Avidin)在HGFI和HFB上吸附, 结果表明, pH和离子强度对BSA和Avidin在HGFI和HFB上吸附有显著影响, 说明BSA和Avidin在两种疏水蛋白上吸附的主要驱动力为静电力. 本文研究结果为实现疏水蛋白表面可控地固定蛋白质提供了理论指导.     

高分子纳米材料与血浆蛋白的相互作用

由于纳米材料具有独特的物理和化学性能,使其在许多领域被广泛应用。纳米材料使用的日益增多要求我们仔细评估其难以预料的毒性（细胞毒性、溶血毒性、血液毒性和免疫毒性）和生物学相互作用。到目前为止,已有大量的研究旨在探索纳米材料与人的细胞或蛋白之间的相互作用,也取得了一些重要成果。在临床应用中,有些生物医用纳米材料常通过静脉注射、渗透、溶解和扩散等方式引入到血液组织中。血液是一种高度复杂的组织,主要由红细胞、白细胞、血小板和血浆组成。其中血浆是一个复杂的体液,它包含超过3700种不同的蛋白质。无论采用哪种方式,这些纳米材料将不可避免地会与丰富的血浆蛋白（或其他血液成分）发生某种联系和相互作用。然而,纳米材料和血浆蛋白之间的相互作用,可能在决定纳米材料的毒性方面起到至关重要的作用。目前对纳米材料与血浆蛋白（或其他血液成分）在分子水平会发生怎样的相互作用知之甚少。本文主要综述了典型的三类高分子纳米材料（包括聚阳离子,高分子胶束和药物（基因）/载体复合纳米粒子）与血浆蛋白的相互作用以及研究这些相互作用相关的分析技术的研究进展,这些内容对体内使用的纳米材料的分子设计和血液安全性非常重要。     

功能蛋白纳米材料在环境保护中的应用

蛋白质是一类结构稳定、官能基团丰富的生物大分子.近年来基于功能蛋白纳米材料的改性制备逐渐成为环境领域的研究热点.其中多巴胺、淀粉样纤维和蛋白质杂化纳米花是最具代表性的三类功能蛋白纳米材料.受海洋生物贻贝启发,多巴胺在碱性条件下可氧化自聚成富有黏性的聚多巴胺涂层广泛用于界面改性;淀粉样纤维是功能蛋白经热处理或化学变性形成...     

气相白炭黑表面处理率的影响因素及判定

气相白炭黑是一种二氧化硅纳米材料，气相白炭黑的最主要应用是用于硅橡胶的补强，但气相白炭黑在硅橡胶中很难分散，影响了补强效果，本文用六甲基二硅氮烷对白炭黑进行表面处理并对白炭黑表面处理率问题做一些探讨。     

一步可控合成二氧化硅纳米管和空心球

通过简单的溶胶凝胶法在相同体系中可控合成了新颖有序的二氧化硅纳米管和空心球,对制备二氧化硅纳米管的多种反应条件进行了系统研究。发现反应时间、溶液中水和乙醇比例、搅拌和滴加速度对形成管状结构都有着重要影响。同时,纳米管的形成机理研究表明,在醇水混合溶液中柠檬酸三铵晶体为细柱状形貌,其作为重要的结构导向剂为二氧化硅胶晶附着提供模板,从而形成管状结构,二氧化硅空心球也显示了相似的形成过程。     

Multivalent-Interaction-Driven Assembly of Discrete,Flexible, and Asymmetric Supramolecular Protein Nano-Prisms

Current approaches to design monodisperse protein assemblies require rigid, tight, and symmetric interactions between oligomeric protein units. Herein, we introduce a new multivalent-interaction-driven assembly strategy that allows flexible, spaced, and asymmetric assembly between protein oligomers. We discovered that two polygonal protein oligomers (ranging from triangle to hexagon) dominantly form a discrete and stable two-layered protein prism nanostructure via multivalent interactions between fused binding pairs. We demonstrated that protein nano-prisms with long flexible peptide linkers (over 80 amino acids) between protein oligomer layers could be discretely formed. Oligomers with different structures could also be monodispersely assembled into two-layered but asymmetric protein nano-prisms. Furthermore, producing higher-order architectures with multiple oligomer layers, for example, 3-layered nano-prisms or nanotubes, was also feasible.     

Modeling the Dynamics of Protein–Protein Interfaces,How and Why?

Protein–protein assemblies act as a key component in numerous cellular processes. Their accurate modeling at the atomic level remains a challenge for structural biology. To address this challenge, several docking and a handful of deep learning methodologies focus on modeling protein–protein interfaces. Although the outcome of these methods has been assessed using static reference structures, more and more data point to the fact that the interaction stability and specificity is encoded in the dynamics of these interfaces. Therefore, this dynamics information must be taken into account when modeling and assessing protein interactions at the atomistic scale. Expanding on this, our review initially focuses on the recent computational strategies aiming at investigating protein–protein interfaces in a dynamic fashion using enhanced sampling, multi-scale modeling, and experimental data integration. Then, we discuss how interface dynamics report on the function of protein assemblies in globular complexes, in fuzzy complexes containing intrinsically disordered proteins, as well as in active complexes, where chemical reactions take place across the protein–protein interface.     

Chitin-binding antifungal protein from <Emphasis Type="Italic">Ficus carica</Emphasis> latex

A low-molecular-weight protein with antifungal activity was isolated from freshly collected latex of the Inzhir tree (Ficus carica L.) by successive affinity chromatography over chitin, cation-exchange chromatography over SP-Sephadex C-50, and reversed-phase HPLC. The molecular weight of 6481 and the partial N-terminus sequence of the protein were determined (MALDI-TOFMS). __________ Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 171–173, March–April, 2008.     

Detection of discriminative sequence motifs in proteins obtained from prokaryotes grown at various temperatures

Recent investigations on the stability of proteins have demonstrated various structural factors, but few have considered sequence factors such as protein motifs. These motifs represent highly conserved regions and describe critical regions that may only exist on proteins that remain functional at high temperatures. This investigation presents a method for identifying and comparing corresponding mesophilic and thermophilic sequence motifs between protein families. Discriminative motifs that are conserved only in the mesophilic or thermophilic subfamily are identified. Analysis of the results shows that, although the subfamilies of most protein families share similar motifs, some discriminative motifs are present in particular thermophilic/mesophilic subfamilies. The thermophilic discriminative motifs are conserved only in thermophilic organisms, revealing that physiochemical principles support thermostability.     

An Off‐Pathway Folding Intermediate of an Acyl Carrier Protein Domain Coexists with the Folded and Unfolded States under Native Conditions

A protein can exist in multiple states under native conditions and those states with low populations are often critical to biological function and self‐assembly. To investigate the role of the minor states of an acyl carrier protein, NMR techniques were applied to determine the number of minor states and characterize their structures and kinetics. The acyl carrier protein from Micromonospora echinospora was found to exist in one major folded state (95.2 %), one unfolded state (4.1 %), and one intermediate state (0.7 %) under native conditions. The three states are in dynamic equilibrium and the intermediate state very likely adopts a native‐like structure and is an off‐pathway folding product. The intermediate state may mediate the formation of oligomers in vitro and play an important role in the recognition of partner enzymes in vivo.     

Substitution of an Internal Disulfide Bridge with a Diselenide Enhances both Foldability and Stability of Human Insulin

Insulin analogues, mainstays in the modern treatment of diabetes mellitus, exemplify the utility of protein engineering in molecular pharmacology. Whereas chemical syntheses of the individual A and B chains were accomplished in the early 1960s, their combination to form native insulin remains inefficient because of competing disulfide pairing and aggregation. To overcome these limitations, we envisioned an alternative approach: pairwise substitution of cysteine residues with selenocysteine (Sec, U). To this end, Cys^A6 and Cys^A11 (which form the internal intrachain A6–A11 disulfide bridge) were each replaced with Sec. The A chain[C6U, C11U] variant was prepared by solid-phase peptide synthesis; while sulfitolysis of biosynthetic human insulin provided wild-type B chain-di-S-sulfonate. The presence of selenium atoms at these sites markedly enhanced the rate and fidelity of chain combination, thus solving a long-standing challenge in chemical insulin synthesis. The affinity of the Se-insulin analogue for the lectin-purified insulin receptor was indistinguishable from that of WT-insulin. Remarkably, the thermodynamic stability of the analogue at 25 °C, as inferred from guanidine denaturation studies, was augmented (ΔΔG_u ≈0.8 kcal mol⁻¹). In accordance with such enhanced stability, reductive unfolding of the Se-insulin analogue and resistance to enzymatic cleavage by Glu-C protease occurred four times more slowly than that of WT-insulin. 2D-NMR and X-ray crystallographic studies demonstrated a native-like three-dimensional structure in which the diselenide bridge was accommodated in the hydrophobic core without steric clash.     

Cellular Synthesis and X-ray Crystal Structure of a Designed Protein Heterocatenane

Herein, we report the biosynthesis of protein heterocatenanes using a programmed sequence of multiple post-translational processing events including intramolecular chain entanglement, in situ backbone cleavage, and spontaneous cyclization. The approach is general, autonomous, and can obviate the need for any additional enzymes. The catenane topology was convincingly proven using a combination of SDS-PAGE, LC-MS, size exclusion chromatography, controlled proteolytic digestion, and protein crystallography. The X-ray crystal structure clearly shows two mechanically interlocked protein rings with intact folded domains. It opens new avenues in the nascent field of protein-topology engineering.     

SpyTag/SpyCatcher Cyclization Confers Resilience to Boiling on a Mesophilic Enzyme

SpyTag is a peptide that spontaneously forms an amide bond with its protein partner SpyCatcher. SpyTag was fused at the N terminus of β‐lactamase and SpyCatcher at the C terminus so that the partners could react to lock together the termini of the enzyme. The wild‐type enzyme aggregates above 37 °C, with irreversible loss of activity. Cyclized β‐lactamase was soluble even after heating at 100 °C; after cooling, the catalytic activity was restored. SpyTag/SpyCatcher cyclization led to a much larger increase in stability than that achieved through point mutation or alternative approaches to cyclization. Cyclized dihydrofolate reductase was similarly resilient. Analyzing unfolding through calorimetry indicated that cyclization did not increase the unfolding temperature but rather facilitated refolding after thermal stress. SpyTag/SpyCatcher sandwiching represents a simple and efficient route to enzyme cyclization, with potential to greatly enhance the robustness of biocatalysts.