Dissecting Cooperative Communications in a Protein with a High‐Throughput Single‐Molecule Scalpel

Miscued communication often leads to misfolding and aggregation of the proteins involved in many diseases. Owing to the ensemble average property of conventional techniques, detailed communication diagrams are difficult to obtain. Mechanical unfolding affords an unprecedented perspective on cooperative transitions by observing a protein along a trajectory defined by two mutated cysteine residues. Nevertheless, this approach requires tedious sample preparation at the risk of altering native protein conformations. To address these issues, we applied click chemistry to tether a protein to the two dsDNA handles through primary amines in lysine residues as well as at the N terminus. As a proof of concept, we used laser tweezers to mechanically unfold and refold calmodulin along 36 trajectories, maximally allowed by this strategy in a single batch of protein preparation. Without a priori knowledge of the particular residues to which the double‐stranded DNA handles attach, we used hierarchical cluster analysis to identify 20 major trajectories, according to the size and the pattern of unfolding transitions. We dissected the cooperativity into all‐or‐none and partially cooperative events, which represent strong and weak high‐order interactions in proteins, respectively. Although the overall cooperativity is higher within the N or C lobe than that between the lobes, the all‐or‐none cooperativity is anisotropic among different the unfolding trajectories and becomes relatively more predominant when the size of the protein segments increases. The average cooperativity for all‐or‐none transitions falls within the expected range observed by ensemble techniques, which supports the hypothesis that unfolding of a free protein can be reconstituted from individual trajectories.     

Cooperative Lewis Pairs Based on Late Transition Metals: Activation of Small Molecules by Platinum(0) and B(C6F5)3

A Lewis basic platinum(0)–CO complex supported by a diphosphine ligand and B(C₆F₅)₃ act cooperatively, in a manner reminiscent of a frustrated Lewis pair, to activate small molecules such as hydrogen, CO₂, and ethene. This cooperative Lewis pair facilitates the coupling of CO and ethene in a new way.     

Chlorophyll sensitized BiVO4 as photoanode for solar water splitting and CO2 conversion

Converting solar energy into valuable hydrogen and hydrocarbon fuels through photoelectrocatalytic water splitting and CO_2 reduction is highly promising in addressing the growing demand for renewable and clean energy resources. However, the solar-to-fuel conversion efficiency is still very low due to limited light absorption and rapid bulk recombination of charge carriers. In this work, we present chlorophyll(Chl) and its derivative sodium copper chlorophyllin(ChlCuNa), as dye sensitizers, modified BiVO_4 to improve the photoelectrochemical(PEC) performance. The photocurrent of BiVO_4 is surprisingly decreased after a direct sensitization of Chl while the sensitization of ChlCuNa obviously enhances photocurrent of BiV04 electrodes by improved surface hydrophilicity and extended light absorption.ChlCuNa-sensitized BiV04 achieves an improved H_2 evolution rate of 5.43 μmol h~(-1) cm~(-2) in water splitting and an enhanced HCOOH production rate of 2.15 μmol h~(-1) cm~(-2) in CO_2 PEC reduction, which are1.9 times and 2.4 times higher than pristine BiVO_4, respectively. It is suggested that the derivative ChlCuNa is a more effective sensitizer for solar-to-fuel energy conversion and CO_2 utilization than Chl.     

叶绿素敏化二氧化钛纳米管电极光电性能及其增强机理

为了研究叶绿素的敏化机理,本文以菠菜叶片叶绿素的乙醇浸提液敏化纳米管TiO_2电极,在Na2SO4水溶液电解液中测定其光电性能。敏化电极的光电流响应曲线显示,叶绿素浸提液敏化纳米管TiO_2电极时会显著改变电极的光电流值,而敏化Ti电极时则产生光电流极小。电极的循环伏安曲线则表明,叶绿素浸提液使电极上的氧化反应更容易发生。测定不同浓度的叶绿素浸提液敏化纳米管TiO_2电极的单色光光电转化效率(IPCE)图谱,结果表明,合适的叶绿素浓度(7.123~71.23μg/L)使电极IPCE平均增加2倍以上,但浓度增大至7123μg/L时,其敏化电极IPCE则明显降低;同时发现叶绿素的敏化作用未明显改变TiO_2电极IPCE图谱的特征谱峰位置。根据实验数据和结果,得出在水溶液中叶绿素改变纳米管TiO_2光电性能的机理,主要是通过叶绿素分子与TiO_2电极中的光生空穴发生反应,进而减少光生电子与空穴的复合,使电极有效光生电子数量增加,光电流密度增大,最终提高TiO_2电极的IPCE。     

区域低碳协同发展评价:京津冀、长三角和珠三角城市群的比较分析

京津冀、长三角和珠三角城市群是中国经济高度发达、最具发展潜力的区域,在低碳发展方面起到引领作用.从经济、资源、环境和绩效的角度构建区域低碳协同发展评价指标体系,采用结合逼近理想解的TOPSIS方法、灰色关联理论和距离协同模型,利用2005~2014年三大城市群50个城市数据实证分析了三大城市群的低碳协同发展程度.结果表明,三大城市群低碳协同发展度整体上呈现上升趋势,其低碳协同程度从高到底依次为长三角、珠三角和京津冀城市群.     

Metal–Support Cooperative Catalysts for Environmentally Benign Molecular Transformations

Metal–support cooperative catalysts have been developed for sustainable and environmentally benign molecular transformations. The active metal centers and supports in these catalysts could cooperatively activate substrates, resulting in high catalytic performance for liquid‐phase reactions under mild conditions. These catalysts involved hydrotalcite‐supported gold and silver nanoparticles with high catalytic activity for organic reactions such as aerobic oxidation, oxidative carbonylation, and chemoselective reduction of epoxides to alkenes and nitrostyrenes to aminostyrenes using alcohols and CO/H₂O as reducing reagents. This high catalytic performance was due to cooperative catalysis between the metal nanoparticles and basic sites of the hydrotalcite support. To increase the metal–support cooperative effect, core–shell nanostructured catalysts consisting of gold or silver nanoparticles in the core and ceria supports in the shell were designed. These core–shell nanocomposite catalysts were effective for the chemoselective hydrogenation of nitrostyrenes to aminostyrenes, unsaturated aldehydes to allyl alcohols, and alkynes to alkenes using H₂ as a clean reductant. In addition, these solid catalysts could be recovered easily from the reaction mixture by simple filtration, and were reusable with high catalytic activity.     

Self-assembly approach toward chiral bimetallic catalysts: bis-urea-functionalized (salen)cobalt complexes for the hydrolytic kinetic resolution of epoxides

A series of novel bis-urea-functionalized (salen)Co complexes has been developed. The complexes were designed to form self-assembled structures in solution through intermolecular urea-urea hydrogen-bonding interactions. These bis-urea (salen)Co catalysts resulted in rate acceleration (up to 13 times) in the hydrolytic kinetic resolution (HKR) of rac-epichlorohydrin in THF by facilitating cooperative activation, compared to the monomeric catalyst. In addition, one of the bis-urea (salen)Co(III) catalyst efficiently resolves various terminal epoxides even under solvent-free conditions by requiring much shorter reaction time at low catalyst loading (0.03-0.05 mol %). A series of kinetic/mechanistic studies demonstrated that the self-association of two (salen)Co units through urea-urea hydrogen bonds was responsible for the observed rate acceleration. The self-assembly study with the bis-urea (salen)Co by FTIR spectroscopy and with the corresponding (salen)Ni complex by (1)H NMR spectroscopy showed that intermolecular hydrogen-bonding interactions exist between the bis-urea scaffolds in THF. This result demonstrates that self-assembly approach by using non-covalent interactions can be an alternative and useful strategy toward the efficient HKR catalysis.     

Lewis acid/base catalyzed [2+2]-cycloaddition of sulfenes and aldehydes: a versatile entry to chiral sulfonyl and sulfinyl derivatives

The first catalytic asymmetric synthesis of β-sultones is reported. This development has enabled a rapid access to a number of highly enantioenriched biologically interesting sulfonyl and sulfinyl compound classes, which makes use of the inherent ring strain of the four-membered heterocycles. The products possess either two vicinal stereocenters, such as in β-hydroxy-sulfonamides, -sulfonates, -sulfones, -sulfonic acids, -sulfinic acids, γ-sultines, and γ-sultones or a single stereocenter, such as in α-branched alkyl or allyl sulfonic acids. This work also represents the first application of sulfene intermediates in asymmetric catalysis. The reactivity of a sulfene normally acting as an electrophile could be reverted by the formation of a nucleophilic zwitterionic sulfene-amine adduct. To achieve a combination of high enantioselectivity and reactivity, cooperative catalytic action of a chiral nucleophilic tertiary amine (the cinchona alkaloid derivative diydroquinine 2,5-diphenyl-4,6-pyrimidinediyl diether ((DHQ)(2)PYR)) and Bi(OTf)(3) or In(OTf)(3) was of primary importance.