Chemistry and Biology of Cylindrols: Novel Inhibitors of Ras Farnesyl-Protein Transferase from Cylindrocarpon lucidum

Farnesyl-protein transferase (FPTase) is an enzyme responsible for the farnesylation of Ras protein. Farnesylation is required for cell-transforming activity in several tumor-types, and therefore, inhibition of FPTase activity may be a potential target for anticancer drugs. Our continued search for novel inhibitors led to the isolation of a number of bicyclic resorcinaldehyde cyclohexanone derivatives named here cylindrols A(1) to A(4), cylindrols B and B(1), and a number of known compounds, from Cylindrocarpon lucidum. The compounds were isolated by bioassay-guided separation using Sephadex LH-20, silica gel, and reverse phase HPLC. Structures were elucidated by extensive application of 2D NMR and X-ray crystallography. The determination of absolute stereochemistry was accomplished by CD measurements. Chemical transformations of the most abundant compound resulted in a number of key derivatives which were critical for the evaluation of structure activity relationship. These compounds are members of ascochlorin family and showed a wide range of inhibitory activity (0.7 &mgr;M to >140 &mgr;M) against FPTase. The FPTase activity was noncompetitive with respect to both substrates. Isolation, structures, chemical transformations, and FPTase activity are discussed in detail.     

Kinetics and efficiency displayed by supported and suspended TiO2 catalysts applied to the disinfection of Escherichia coli

TiO₂-mediated photocatalysis is widely used in a variety of applications and products in the environmental and energy fields, including photoelectrochemical conversion, self-cleaning surfaces, and especially water purification systems. The dimensionality of the structure of a TiO₂ material can affect its properties, functions, and more specifically, its photocatalytic performance. In this work, the photocatalytic inactivation of Gram-negative Escherichia coli using three photocatalysts, differing in their structure and other characteristics, was studied in a batch reactor under UVA light. The aim was to establish the disinfection efficiency of solid TiO₂ compared with that of suspended catalysts, widely considered as reference cases for photocatalytic water disinfection. The bacterial inactivation profiles obtained showed that: (1) the photoinactivation was exclusively related to the quantity of photons retained per unit of treated volume, irrespective of the characteristics of the photocatalyst and the emitted light flux densities; (2) across the whole UV light range studied, each of the photocatalytic solids was able to achieve more than 2 log bacterial inactivation with less than 2 h UV irradiation; (3) none of the used catalysts achieved a total bacterial disinfection during the treatment time. For each of the catalysts the quantum yield has been assessed in terms of disinfection efficiency, the 2D material showed almost the same performance as those of suspended catalysts. This catalyst is promising for supported photocatalysis applications.     

光的碰撞再分布

光的碰撞再分布是２０多年来发展起来的研究原子碰撞过程的新技术，目前已成为研究原子相互作用的强有力的工具。文章简要介绍了碰撞再分布技术的基本原理和典型实验，并给出了应用实例。     

102Ru核振动到转动演化的微观研究

基于微观sdIBM-2方案和实验单粒子能量值, 在最普遍的哈密顿量下, 用两组不同的核子-核子等效相互作用参数, 分别很好地再现了¹⁰²Ru核的振动带能谱和转动带能谱及其演化过程. 微观和唯象的研究指认: 1) 这两种激发模式的共存区是能态8⁺₁—12⁺₁(即E_x=2.500—4.000 MeV); 态 8⁺_{1关键词： 微观sdIBM-2方案 形状演化 玻色子 102Ru核')" href="#">¹⁰²Ru核}     

102Ru核振动到转动演化的微观研究

基于微观sdIBM-2方案和实验单粒子能量值,在最普遍的哈密顿量下,用两组不同的核子.核子等效相互作用参数,分别很好地再现了102Ru核的振动带能谱和转动带能谱及其演化过程.微观和唯象的研究指认:1)这两种激发模式的共存区是能态81 -121 (即Ex=2.500-4.000 MeV);态81 是振动模式占据优势的能态,态121 是转动模式占据优势的能态,而状态101 则是两种模式的中立能态;2)态121 是141 态退耦到态101 辐射光子相变后的中间能态;3)从基态起直到201 态的yrast态全都是集体态,而以后出现的第一个拆对顺排态很可能就是中子h11/2的两准粒子态;4)这种结构的过渡不是很剧烈的,而是通过玻色子结构常数在过渡区中不大的改变来实现的.     

Alcohol uncaging with fluorescence reporting: evaluation of o-acetoxyphenyl methyloxazolone precursors

This paper evaluates a series of photolabile protecting groups with built-in fluorescence reporting. They rely on readily available o-acetoxyphenyl methyloxazolones as activated precursors. Alcohol substrates are easily caged. The resulting photoactivable esters exhibit large one- and two-photon uncaging cross sections. The alcohol substrates are quantitatively released in a 1:1 molar ratio with a strongly fluorescent coumarin coproduct that serves as a reporter to quantify substrate delivery.     

76Sr核yrast带结构演化的微观研究

对于发生在同一个原子核中的、从一种高有序激发模式向着另一种低有序激发模式演化的机理和物理图像,提出了一种新的理解：被布居到高角动量态的高有序激发核,以E₂跃迁方式先行退耦到yrast带,再退耦到共存区时释放了结构能,诱发价核子对耦合强度改变,重新组合出低有序的激发模式基准态,实现了基准态结构的过渡.从微观上看,这是一种既温和而又平稳的转变.并以⁷⁶Sr核为例作了深入阐述. 关键词： 量子相变 yrast带结构演化 微观sdIBM-2方案 76Sr核')" href="#">⁷⁶Sr核     

相对论连续谱Hartree-Bogoliubov理论对Dy偶同位素链的研究

基于相对论连续谱Hartree-Bogoliubov(RCHB)理论, 在NL-SH参数下, 研究了从质子滴线到中子滴线Dy的整个偶同位素链的基态特性. 首先, 计算的核结合能和核均方根半径结果, 在有实验数据进行比较的范围内, 相当好地与已有实验数据值符合; 其次, 在中子数为N=82—126的壳层里, 在84—92, 94—126之间有明显的子壳层结构; $^{250}_{66}\rm Dy_{184}$核是中子滴线核; 在$_{\hspace{5ex}66}^{\text{240—250}}\rm Dy_{\text{174—184}}$范围内有晕核的典型特征, 这里很可能存在有巨晕核.     

Ultrasonic characterization of proteins and blood cells

Ultrasound changes its intensity and speed when propagating through a liquid or a suspension containing particles. In addition it generates a weak electric signal by altering the motion of ions and charged particles. Hence acoustic and electroacoustic measurements provide information about the properties of suspended particles and molecules. Here we present both acoustic and electroacoustic results on blood suspensions and protein solutions, relevant to life sciences. For blood cells a strong increase in acoustic attenuation with volume fraction is found, from which the speed of sound in an erythrocyte is found to be about 1900 m/s, assuming the attenuation is due to scattering only. A similar value of 1700 m/s is found from the increase in sound speed of the dispersion with concentration. Electroacoustic measurements on bovine serum albumin (BSA) yield a charge of about seven elementary charges per BSA molecule. These results show the power and usefulness of acoustic and electroacoustic measurement techniques for biological systems.