生物氧化还原研究中的薄层电化学技术

标准氧化还原电位 E~(0′)和电子转移化学计量数 n 的测定是生物氧化还原体系研究中的一个重要方面.由于许多生物分子会在电极上吸附,有些蛋白分子的氧化还原中心位于蛋白结构的内部,它们同电极的异相电子转移过程很不可逆或非常缓慢,因而难于用常规的电化学方法进行 E_(0′)和 n 值的测量。近年来薄层电化学技术的发展为这方面的研究打开了方便之门,本文简要介绍其原理及应用。     

氧化还原蛋白质在模拟生物膜修饰电极上的直接电化学

评述了氧化还原蛋白在模拟生物膜这种新型的化学修饰电极上的直接电化学研究的进展。对蛋白质在表面活性剂薄膜电极和多层复合薄膜电极上的电化学行为、模拟生物膜的超分子结构以及蛋白质在该类薄膜修饰电极上对不同底物的电催化性质进行了较详细的介绍。     

FeTPP和CoTPP电化学氧化还原的量子化学研究

用限制性的CNDO/2方法研究了FeTPP和CoTPP不同还原阶段的电子结构,结果表明,在FeTPP还原反应中第一个还原电子和Fe的d轨道相作用,第二个还原电子与卟啉环的4个氮原子及同它相连的8个碳原子的p轨道相作用,而CoTPP的2个还原电子与Co的d轨道相互作用,这与紫外原位光谱的实验结果完全一致。     

漆酶的生物电化学研究

漆酶属于蓝多铜氧化酶家族,在自然界尤其是真菌中广泛存在.漆酶在催化多种底物氧化的同时,伴随氧一步四电子直接还原生成水,铜离子活性中心作为辅助基团,参与电子传递过程.漆酶这一良好的电化学特性使其成为生物阴极的理想催化剂.本文综述了漆酶作为具有生物活性的氧化还原蛋白质在电化学领域的研究情况,从漆酶的结构及来源、生物电催化反...     

氧化还原蛋白质的电荷传递及界面行为

本文综述了近年来氧化还原蛋白质电子传递与界面行为研究领域的最新进展.主要基于作者所在实验室并参考其他实验室的研究成果,总结了蛋白质与电极间的直接电子传递、蛋白质热力学和动力学性质、蛋白质的催化活性及其调节等相关领域的工作进展.近几年的研究表明,电化学技术已成为蛋白质研究的重要工具,对于氧化还原蛋白质的电子传递与界面行为的研究更是一种有效的技术手段.     

蛋白质修饰的电化学研究

蛋白质的翻译后修饰对于生命体执行正常的生理功能具有十分重要的作用,是蛋白质科学研究的重要内容.目前研究蛋白质修饰的方法主要有质谱法、亲和层析等,然而由于蛋白质修饰研究的复杂性,迫切需要发掘新的技术手段.电化学方法理论成熟、应用广泛,在生命科学许多领域发挥着越来越重要的作用.蛋白质的体外修饰必将导致蛋白质特定位点基团的变化,可以利用巧妙设计的电化学方法予以表征和分析,以期探明修饰对蛋白质结构和功能的影响.此外,又可以利用电化学定量分析的独特优势快速准确地测定蛋白质修饰中涉及的相关酶活.正因为如此,蛋白质体外修饰的电化学研究已引起越来越多的关注.本文以作者课题组近期研究工作为主,结合国内外同行的相关代表性工作,介绍电化学方法在蛋白质修饰方面的近期研究进展,并探讨了今后的发展方向和趋势.     

电化学还原的氧化石墨烯修饰电极检测L-色氨酸

制备了氧化石墨烯修饰玻碳电极,并运用循环伏安法对氧化石墨烯进行了直接的电化学还原,研究了L-色氨酸在该电化学还原的氧化石墨烯修饰玻碳电极上的电化学行为。结果表明,L-色氨酸在该修饰电极上其氧化峰电流与裸玻碳电极相比增大了7.1倍,且峰电位负移80mV。利用差分脉冲伏安法,在pH=6.5的磷酸盐缓冲溶液中测定L-色氨酸,氧化峰电流与其浓度在0.4～65.0μmol/L范围内呈良好的线性关系,相关系数为0.998,方法检出限为0.2μmol/L。     

电化学还原氧化石墨烯用于四环素电催化检测

四环素(TTC)因其广泛的抗菌性和低生产成本等特点而成为应用最广泛的兽医药物. TTC的大量使用不可避免地导致其进入地表水、地下水和污水处理厂.迄今,已有许多方法用于TTC检测,包括免疫测定法、微生物检测法和化学-物理法等.然而,这些方法费用高,耗时长或需要复杂的样品预处理过程,不适合现场测量或常规分析.电化学分析法具有操作简单、成本低廉、选择性和灵敏度较高、易实现在线检测等特点,在检测领域具有重要优势.石墨烯在电化学传感器领域表现出优越的应用性能,但有关石墨烯材料应用于电分析和电催化方面的报道仍然有限.石墨烯的前驱体氧化石墨烯(GO)片层底面上具有各种类型的含氧官能团和层状边缘,导致其绝缘并具有很多缺陷,使GO包含了sp2和sp3杂化碳原子,为GO提供了独特的具有化学功能的异构电子结构.通过对GO进行还原,可以生成新的sp2域或者改变含氧官能团的数量和类型,从而为GO提供更多的特殊性质.研究表明,电化学还原是一种绿色快速的还原方法,可以控制GO的还原程度和还原过程.本文利用电化学还原法来调整GO表面的官能团和缺陷度,利用在–0.8 V还原电位下得到的电化学还原氧化石墨烯(ERGO-0.8V)修饰玻碳电极(GC)为工作电极(GC/ERGO-0.8V),采用循环伏安法对溶解在pH=3的缓冲溶液中的TTC进行电化学检测,发现ERGO-0.8V对TTC具有电催化性能.利用红外光谱(FT-IR)、X射线光电子能谱(XPS)和拉曼光谱对ERGO-0.8V, ERGO-1.2V, GO及化学还原得到的石墨烯(CRGO)表面官能团和缺陷程度进行了表征,考察了TTC在ERGO-0.8V/GC上的电化学行为,对其电催化还原机理进行了推测.结果表明,与GO, ERGO-1.2V及CRGO修饰电极相比, GC/ERGO-0.8V修饰电极的催化还原峰在0–0.5 V,对TTC表现出独特的电催化性能, GC/ERGO-0.8V电极对浓度为0.1–120 mg/L的TTC溶液具有良好的检测性能,在不同浓度范围内其氧化峰峰电流与峰电位的线性关系不同. FT-IR和XPS结果显示,在–0.8 V还原电位下得到的ERGO-0.8V,其官能团类型和数量发生变化,但仍存在大量官能团,主要是羧基、羟基和环氧基.同时,拉曼表征显示ERGO-0.8V的缺陷密度增大,同时新生成的sp2域减小而使得ERGO的sp2域减小.对比GO等其他材料的表征结果推测,官能团变化是影响ERGO独特电催化性质的主要因素,除此之外还有材料的缺陷度和sp2域.推测GC/ERGO-0.8V修饰电极对TTC可能的催化机理为： TTC在GC/ERGO电极上的还原与氢醌和醌之间的转换有关;而对于ERGO,则可能对应于羧基和羟基之间的转化.然而,同样具有羧基和羟基的ERGO-1.2V则对TTC没有产生电催化作用.其原因可能是在–0.8到–1.2 V还原电位下,形成的羧基位于石墨烯片层内部,而片层内的电子传递较慢.     

吡啶存在下（TPP）Co的电化学氧化还原行为研究

本文考究了吡啶对Ｃｏ在１，２－二氧乙烷中的电化学氧化还原行的影响，观察到当存在一定量Ｐｙ时，ＣＯ（Ⅲ）／Ｃｏ（Ⅱ）还原过程出现两个还原峰，分别在０．２５和－０．４０Ｖ两处。     

染料修饰电极加速氧化还原蛋白质的电化学反应

评述了染料修饰电极加速氧化还原蛋白质的电子传递反应。讨论了染料修饰电极的修饰方法和性质。简述了伏安法、流动分析、光谱电化学法等几种不同研究方法的应用。提出了可逆电催化反应的机理，并将数值计算与实验结果进行比较、验证。引用了４７篇文献。     

Spatial and Kinetic Regulation of Sulfur Electrochemistry on Semi-Immobilized Redox Mediators in Working Batteries

Use of redox mediators (RMs) is an effective strategy to enhance reaction kinetics of multi-electron sulfur electrochemistry. However, the soluble small-molecule RMs usually aggravate the internal shuttle and thus further reduce the battery efficiency and cyclability. A semi-immobilization strategy is now proposed for RM design to effectively regulate the sulfur electrochemistry while circumvent the inherent shuttle issue in a working battery. Small imide molecules as the model RMs were co-polymerized with moderate-chained polyether, rendering a semi-immobilized RM (PIPE) that is spatially restrained yet kinetically active. A small amount of PIPE (5 % in cathode) extended the cyclability of sulfur cathode from 37 to 190 cycles with 80 % capacity retention at 0.5 C. The semi-immobilization strategy helps to understand RM-assisted sulfur electrochemistry in alkali metal batteries and enlightens the chemical design of active additives for advanced electrochemical energy storage devices.     

Theoretical Modeling of Redox Potentials of Biomolecules

The estimation of the redox potentials of biologically relevant systems by means of theoretical-computational approaches still represents a challenge. In fact, the size of these systems typically does not allow a full quantum-mechanical treatment needed to describe electron loss/gain in such a complex environment, where the redox process takes place. Therefore, a number of different theoretical strategies have been developed so far to make the calculation of the redox free energy feasible with current computational resources. In this review, we provide a survey of such theoretical-computational approaches used in this context, highlighting their physical principles and discussing their advantages and limitations. Several examples of these approaches applied to the estimation of the redox potentials of both proteins and nucleic acids are described and critically discussed. Finally, general considerations on the most promising strategies are reported.     

Spatial and Kinetic Regulation of Sulfur Electrochemistry on Semi‐Immobilized Redox Mediators in Working Batteries

Use of redox mediators (RMs) is an effective strategy to enhance reaction kinetics of multi‐electron sulfur electrochemistry. However, the soluble small‐molecule RMs usually aggravate the internal shuttle and thus further reduce the battery efficiency and cyclability. A semi‐immobilization strategy is now proposed for RM design to effectively regulate the sulfur electrochemistry while circumvent the inherent shuttle issue in a working battery. Small imide molecules as the model RMs were co‐polymerized with moderate‐chained polyether, rendering a semi‐immobilized RM (PIPE) that is spatially restrained yet kinetically active. A small amount of PIPE (5 % in cathode) extended the cyclability of sulfur cathode from 37 to 190 cycles with 80 % capacity retention at 0.5 C. The semi‐immobilization strategy helps to understand RM‐assisted sulfur electrochemistry in alkali metal batteries and enlightens the chemical design of active additives for advanced electrochemical energy storage devices.     

牙体的电化学研究

牙体的电化学研究乔亦男，张加理（浙江大学化学系杭州３１００２７）（浙江医科大学杭州）关键词生物电化学，生物电位，牙，ＳｒＣｌ２，ＮａＦ生命活动中的生物电化学现象已被科学界所公认［１］，生物体存在着特有的生物电位，如表皮电位、神经电位、脑电位、心脏电位...     

Redox Denaturation of Proteins: Electrochemical Treatment of Egg Plasma

Although acid/base reactions are used widely to denature proteins during food processing, the application of reduction/oxidation (redox) reactions are relatively rare in this field. Herein, we demonstrate a “redox denaturation” of proteins, using egg plasma as a model. Electrochemical treatment of egg plasma in the presence of iodide ion (I^?) selectively induced intramolecular disulfide bond formations, resulting in a different type of denaturation than that achieved via heat treatment. The reaction mechanism was examined through electrochemical analysis using cyclic voltammetry. Although the involvement of hypervalent iodine (“I⁺”) cannot be ruled out, molecular iodine (I₂) generated at the surface of anode is the most likely oxidizing agent that formed the disulfide bonds. We believe that the redox denaturation of proteins described herein would be a promising approach in food processing and can find practical applications in this field.     

质谱电喷雾离子源中电化学与电晕放电氧化还原反应的研究进展

质谱电喷雾离子化过程中包含两类氧化还原反应:电化学氧化还原和电晕放电氧化还原。一方面,这两类反应干扰谱图解析、降低分析物的检测灵敏度;另一方面,利用氧化还原的特性可发展新型离子源,提高电喷雾离子化过程中难离子化化合物的离子化效率,研究蛋白质相互作用等。该文系统地介绍了国内外对于电化学氧化还原反应和电晕放电氧化还原反应的最近研究进展,主要包括此两类反应的弊端、应用价值,以及控制两类反应的方法。最后总结了区分两种反应的方法,并对电喷雾离子源的发展进行了展望。     

Recent Advances in Photoinduced Modification of Amino Acids,Peptides, and Proteins

The chemical modification of biopolymers like peptides and proteins is a key technology to access vaccines and pharmaceuticals. Similarly, the tunable derivatization of individual amino acids is important as they are key building blocks of biomolecules, bioactive natural products, synthetic polymers, and innovative materials. The high diversity of functional groups present in amino acid-based molecules represents a significant challenge for their selective derivatization Recently, visible light-mediated transformations have emerged as a powerful strategy for achieving chemoselective biomolecule modification. This technique offers numerous advantages over other methods, including a higher selectivity, mild reaction conditions and high functional-group tolerance. This review provides an overview of the most recent methods covering the photoinduced modification for single amino acids and site-selective functionalization in peptides and proteins under mild and even biocompatible conditions. Future challenges and perspectives are discussed beyond the diverse types of photocatalytic transformations that are currently available.     

Enhanced Electrosynthetic Hydrogen Evolution by Hydrogenases Embedded in a Redox-Active Hydrogel

Molecular hydrogen is a major high-energy carrier for future energy technologies, if produced from renewable electrical energy. Hydrogenase enzymes offer a pathway for bioelectrochemically producing hydrogen that is advantageous over traditional platforms for hydrogen production because of low overpotentials and ambient operating temperature and pressure. However, electron delivery from the electrode surface to the enzyme's active site is often rate-limiting. Here, it is shown that three different hydrogenases from Clostridium pasteurianum and Methanococcus maripaludis, when immobilized at a cathode in a cobaltocene-functionalized polyallylamine (Cc-PAA) redox polymer, mediate rapid and efficient hydrogen evolution. Furthermore, it is shown that Cc-PAA-mediated hydrogenases can operate at high faradaic efficiency (80–100 %) and low apparent overpotential (−0.578 to −0.593 V vs. SHE). Specific activities of these hydrogenases in the electrosynthetic Cc-PAA assay were comparable to their respective activities in traditional methyl viologen assays, indicating that Cc-PAA mediates electron transfer at high rates, to most of the embedded enzymes.     

Direct Electrochemistry of Cytochrome c at Modified Si(100) Electrodes

This paper demonstrates the direct electron transfer between the heme moiety of horse hearth cytochrome c and a pyridinyl group on self‐assembled‐monolayer‐modified Si(100) electrodes. Self‐assembled monolayers (SAMs) containing the putative receptor ligand were prepared by a step‐wise procedure using “click” reactions of acetylene‐terminated alkyl monolayers and isonicotinic acid azide derivatives. Unoxidized Si(100) electrodes, possessing either isonicotinate or isonicotinamide receptor ligands, were characterized using X‐ray photoelectron spectroscopy, contact‐angle goniometry, cyclic voltammetry, and electrochemical impedance spectroscopy. The ability of isonicotinic acid terminated layers to coordinatively bind the redox center of cytochrome c was found to be restricted to pyridinyl assemblies with a para‐ester linkage present. The protocol detailed here offers an experimentally simple modular approach to producing chemically well‐defined SAMs on silicon surfaces for direct electrochemistry of a well‐studied model redox protein.