Oxidatively robust monophenolate-copper(II) complexes as potential models of galactose oxidase

Cupric complexes of a novel phenanthroline-phenolate ligand have strongly distorted coordination geometries and electrochemical properties conducive to modeling the spectroscopy and reactivity of the enzyme galactose oxidase.     

运用密度泛函活性理论的信息论方法研究苯并富烯衍生物的芳香性

文献中已有越来越多的芳香性体系被发现,同时也有越来越多的芳香性指标被提出来,但是如何解释芳香化合物稳定性的起源以及理解芳香性的本质仍然是当今理论化学中一个悬而未决的难题。运用我们新近提出的密度泛函活性理论信息论方法,不久前我们曾对一系列富烯衍生物进行了系统研究并得到了一个全新的认识。本文进一步探讨苯并富烯衍生物的芳香性行为,目的在于考察一个或多个苯环与富烯连接之后其芳香性发生变化的情况。运用香农熵,费舍尔信息,Ghosh-Berkowitz-Parr熵,Onicescu信息能,信息增益,以及相对Rényi熵六个信息量,和四种芳香指标,ASE,HOMA,FLU和NICS,我们系统地研究了信息量和芳香性指标在单、双、三苯并富烯衍生物中的相关性。我们发现,不管是否有苯环与富烯相连,芳香指标和信息量的交叉相关性都是一样的。这表明,虽然苯环本身具有芳香性,但苯环与富烯相连并不能改变富烯的芳香性与反芳香性本质。苯并富烯衍生物与富烯衍生物的芳香性和反芳香性一致。苯并富烯衍生物的芳香性和反芳香性完全取决于富烯本身的芳香性和反芳香性。这些结果为认识和理解复杂体系芳香性和反芳香性起源和本质将提供有益的启示。     

Synthesis of a new fluorescent probe specific for catechols

[reaction: see text] The synthesis of a new fluorescent probe, specific for the catechol moiety, has been conducted by preparation of alpha,alpha-dibromomalonamides containing an appropriate fluorophore. N,N'-Bis-anthracen-9-ylmethyl-2,2-dibromomalonamide reacted with various catechols in the presence of cesium carbonate to generate highly fluorescent derivatives.     

Three-dimensional tomography using a cubic-phase plate extended depth-of-field system

We use cubic-phase plate imaging to demonstrate an order-of-magnitude improvement in the transverse resolution of three-dimensional objects reconstructed by extended depth-of-field tomography. Our algorithm compensates for the range shear of the cubic-phase approach and uses camera rotation to center the reconstructed volume on a target object point.     

Intramolecular charge transfer and biomimetic reaction kinetics in galactose oxidase model complexes

One-electron oxidation of two structurally similar CuII-diphenolate complexes, 1 and 2, creates EPR-silent CuII-phenoxyl complexes [1]+ and [2]+ that mimic the oxidized form of the enzyme galactose oxidase (GOase). Both model complexes display novel NIR absorptions assigned to phenolate-phenoxyl charge transfer that resemble a tyrosinate-tyrosyl charge-transfer band observed in the enzymatic system. [1]+ and [2]+ react with benzyl alcohol to form 0.5 equivs of benzaldehyde per complex; biomimetic reduction to CuI-phenol complexes is not observed, but such species may exist transiently. Initial kinetic studies show that [2]+ reacts faster with benzyl alcohol than does [1]+, despite being a significantly weaker oxidant (DeltaE degrees = 370 mV). This acceleration is ascribed to mechanistic differences: [2]+ appears to bind substrate prior to the rate-determining step. Large, nonclassical kinetic isotope effects confirm C-H bond cleavage as the rate-determining step in the reactions of both [1]+ and [2]+ with benzyl alcohol, as is the case for GOase.     

Ho2(Co,Si)17化合物的结构与磁晶各向异性

用三弧Czochralski法和真空电弧熔炼法制备了Ho2Co17-xSix化合物.通过X射线衍射和磁性测量手段研究了化合物的结构与内禀磁性.重点讨论了磁晶各向异性和自旋重取向转变.实验结果表明,Ho2Co17为Th2Ni17型六角结构,在0.5≤x≤3的化合物均为Th2Zn17型菱方结构,能够获得单相2:17型化合物的最大Si含量是x=3.在x≤2的浓度范围,化合物的易磁化方向垂直于c轴.随Si含量增加,化合物的居里温度和Co原子平均磁矩单调减少.根据Ho2Co17-xSix化合物的居里温度和自旋重取向温度,获得了磁相图.根据热磁曲线,确定了温度补偿点.在Ho2Co17化合物中观察到了在1005 K发生自旋重取向转变.     

ELLIPSOMETRY OF BLACK LIPID MEMBRANES OF EGG LECITHIN AND CHLOROPLAST EXTRACTS

Abstract— Ellipsometric angles and reflectivity of black lipid membranes containing either egg lecithin or chloroplast extracts were measured at a wavelength of 6328 Å. Evidence was found for positive uniaxial anisotropy in membranes of lecithin. If the thickness of those films is assumed to be 62 Å, the refractive index normal to the film surface is 1.471 ± 0.004, and the refractive index parallel to the film surface is 1.454 ± 0.003. The results for membranes of chloroplast extracts also indicate a positive anisotropy in the indices of absorption.     

Simplest Monodentate Imidazole Stabilization of the oxy‐Tyrosinase Cu2O2 Core: Phenolate Hydroxylation through a CuIII Intermediate

Tyrosinases are ubiquitous binuclear copper enzymes that oxygenate to Cu^II₂O₂ cores bonded by three histidine Nτ‐imidazoles per Cu center. Synthetic monodentate imidazole‐bonded Cu^II₂O₂ species self‐assemble in a near quantitative manner at ?125 °C, but Nπ‐ligation has been required. Herein, we disclose the syntheses and reactivity of three Nτ‐imidazole bonded Cu^II₂O₂ species at solution temperatures of ?145 °C, which was achieved using a eutectic mixture of THF and 2‐MeTHF. The addition of anionic phenolates affords a Cu^III₂O₂ species, where the bonded phenolates hydroxylate to catecholates in high yields. Similar Cu^III₂O₂ intermediates are not observed using Nπ‐bonded Cu^II₂O₂ species, hinting that Nτ‐imidazole ligation, conserved in all characterized Ty, has functional advantage beyond active‐site flexibility. Substrate accessibility to the oxygenated Cu₂O₂ core and stabilization of a high oxidation state of the copper centers are suggested from these minimalistic models.