Ultrafast quenching of tryptophan fluorescence in proteins: Interresidue and intrahelical electron transfer

Quenching of tryptophan fluorescence in proteins has been critical to the understanding of protein dynamics and enzyme reactions using tryptophan as a molecular optical probe. We report here our systematic examinations of potential quenching residues with more than 40 proteins. With site-directed mutation, we placed tryptophan to desired positions or altered its neighboring residues to screen quenching groups among 20 amino acid residues and of peptide backbones. With femtosecond resolution, we observed the ultrafast quenching dynamics within 100 ps and identified two ultrafast quenching groups, the carbonyl- and sulfur-containing residues. The former is glutamine and glutamate residues and the later is disulfide bond and cysteine residue. The quenching by the peptide-bond carbonyl group as well as other potential residues mostly occurs in longer than 100 ps. These ultrafast quenching dynamics occur at van der Waals distances through intraprotein electron transfer with high directionality. Following optimal molecular orbital overlap, electron jumps from the benzene ring of the indole moiety in a vertical orientation to the LUMO of acceptor quenching residues. Molecular dynamics simulations were invoked to elucidate various correlations of quenching dynamics with separation distances, relative orientations, local fluctuations and reaction heterogeneity. These unique ultrafast quenching pairs, as recently found to extensively occur in high-resolution protein structures, may have significant biological implications.     

硫杂蒽酮光敏分解重氮盐及其用作光引发体系的研究

本工作对几种新型硫杂蒽酮化合物敏化光解重氮盐问题进行了研究。工作表明:敏化反应是通过电子转移过程实现的,重氮盐所带取代基以及溶剂对重氮盐的光解有较大影响。十分有趣的是该体系对甲基丙烯酸甲酯进行光敏自由基引发聚合的速率和其光解反应速率有很大的不同,本文对此现象进行了讨论。     

石墨二炔及其电子转移增强特性

石墨二炔是由sp和sp²杂化的碳原子构成的新的碳同素异形体。由于石墨二炔具有独特的拓扑结构和电子结构、较高的电荷迁移率及优异的电子传输性能,使其与其他材料相互作用,可表现出独特的电子转移增强特性。本文基于石墨二炔的电子转移增强特性,概述了石墨二炔及其电子转移增强特性的最新研究进展,包括金属氧化物/石墨二炔、金属纳米颗粒/石墨二炔、聚合物/石墨二炔以及染料分子/石墨二炔等多种石墨二炔基材料。本文从理论和实验研究两个方面详细阐述了石墨二炔的电子转移增强特性、石墨二炔与不同材料的相互作用以及相关的应用。希望该综述能对石墨炔化学的发展起到一定的积极作用。     

Type 1 2HDM as Effective Theory of Supersymmetry

It is generally believed that the low energy effective theory of the minimal supersymmetric standard model is the type 2 two Higgs doublet model.We will show that the type 1 two Higgs doublet model can also be as the effective of supersymmetry in a specific case with high scale supersymmetry breaking and gauge mediation.If the other electroweak doublet obtain the vacuum expectation value after the electroweak symmetry breaking,the Higgs spectrum is quite different.A remarkable feature is that the physical Higgs boson mass can be 125 GeV unlike in the ordinary models with high scale supersymmetry in which the Higgs mass is generally around 140 GeV.     

γ-二氧化锰/K3[Fe(CN)6]溶液界面的电子转移反转区

Marcus电子转移理论的主要成果之一是预言了电子转移反应反转区的存在.从实验上 验证Marcus反转区仍是一个热点问题.通过对γ-MnO2/K3[Fe(CN)6]溶液界面平带电位、极 化曲线的测量,计算了在极化条件下,γ-MnO2导带的电子直接转移到溶液中氧化态物种[F e(CN)6]3-空电子能级上的速率常数ket,logket对外加电位作图,观察到了Marcus反转区. 从理论上也论证了在半导体/溶液界面上的直接电子转移反转区的存在.     

Co(H2O)62+/3+体系电子转移反应动力学的理论研究

A theoretical scheme is presented which is based on an activation model for calculating the rate of the electron- exchange reaction between transition metal complexes in aqueous solution and applies to Co(H2O)6 2+/3+ electron transfer system. The activation parameter and activation energy of the system are obtained via the activation model. The slopes of the potential energy surfaces (curves) of the reacting system at the separated reactants are calculated from the fitted potential energy curves. The coupling matrix element is determined by using the perturbation theory and numerical integral method. Theoretical rate constants are obtained for the system at both UHF/6-311G and UMP2/6-311G levels. The agreement of the theoretical results with experimetal values is excellent. This fact indicates the scheme proposed is feasible and accurate in studying the self- exchange eletron transfer reaction.     

Utility theory in conflict resolution

In this paper, multi-attribute utility theory is extended to accommodate adversarial problem solving situations involving multiple interacting agents. Such situations are resolved by partial goal satisfaction and persuasion, and have only scantily been described in the AI literature. Utility theory is shown to provide a computational framework to (a) generate a compromise solution that partially satisfies the conflicting goals of the agents, (b) evaluate whether a solution is an improvement on a previously rejected one, and (c) determine the effectiveness of persuasive arguments. Our examples are taken from the domain of labor mediation and are implemented in a computer program, called the PERSUADER.     

Electrosynthesis of tryptanthrin

Tryptanthrin is obtained in a high yield by cathodic reduction of isatin via a low-energy consumption process where an electron transfer to the oxygen in air is involved.     

Ni nanoparticles as electron-transfer mediators and NiSx as interfacial active sites for coordinative enhancement of H2-evolution performance of TiO2

The development of efficient photocatalytic H₂-evolution materials requires both rapid electron transfer and an effective interfacial catalysis reaction for H₂ production. In addition to the well-known noble metals, low-cost and earth-abundant non-noble metals can also act as electron-transfer mediators to modify photocatalysts. However, as almost all non-noble metals lack the interfacial catalytic active sites required for the H₂-evolution reaction, the enhancement of the photocatalytic performance is limited. Therefore, the development of new interfacial active sites on metal-modified photocatalysts is of considerable importance. In this study, to enhance the photocatalytic evolution of H₂ by Ni-modified TiO₂, the formation of NiS_x as interfacial active sites was promoted on the surface of Ni nanoparticles. Specifically, the co-modified TiO₂/Ni-NiS_x photocatalysts were prepared via a two-step process involving the photoinduced deposition of Ni on the TiO₂ surface and the subsequent formation of NiS_x on the Ni surface by a hydrothermal reaction method. It was found that the TiO₂/Ni-NiS_x photocatalysts exhibited enhanced photocatalytic H₂-evolution activity. In particular, TiO₂/Ni-NiS_x(30%) showed the highest photocatalytic rate (223.74 μmol h^?1), which was greater than those of TiO₂, TiO₂/Ni, and TiO₂/NiS_x by factors of 22.2, 8.0, and 2.2, respectively. The improved H₂-evolution performance of TiO₂/Ni-NiS_x could be attributed to the excellent synergistic effect of Ni and NiS_x, where Ni nanoparticles function as effective mediators to transfer electrons from the TiO₂ surface and NiS_x serves as interfacial active sites to capture H⁺ ions from solution and promote the interfacial H₂-evolution reaction. The synergistic effect of the non-noble metal cocatalyst and the interfacial active sites may provide new insights for the design of highly efficient photocatalytic materials.     

聚烷基紫精电解质复合物催化偶氮苯的还原研究

本文报道了几种聚烷基紫精复合物的制备, 并研究了作为电子转移催化剂在偶氮苯还原中的作用, 结果显示,聚烷基紫精-聚阴离子复合物具有诱导偶氮苯还原的能力.并且不同聚电解质复合物具有不同的电子转移中介能力.