Computational studies of the primary phototransduction event in visual rhodopsin

This Account addresses recent advances in the elucidation of the detailed molecular rearrangements due to the primary photochemical event in rhodopsin, a prototypical G-protein-coupled receptor (GPCR) responsible for the signal transmission cascade in the vertebrate vision process. The reviewed studies provide fundamental insight on long-standing problems regarding the assembly and function of the individual residues and bound water molecules that form the rhodopsin active site, a center that catalyzes the 11-cis/all-trans isomerization of the retinyl chromophore in the primary step of the phototransduction mechanism. Emphasis is placed on the authors' recent computational studies, based on state-of-the-art quantum mechanics/molecular mechanics (QM/MM) hybrid methods, addressing the structural refinement of the retinyl chromophore binding site in high-resolution X-ray structures of bovine visual rhodopsin, the energy storage mechanism, and the molecular origin of spectroscopic changes due to the primary photochemical event.     

Active coating

Preventing the corrosion of metal substrates by applying an active coating was studied. The active coating was prepared by addition of metal powder and polyaniline in xylene solution. Trials were conducted by coating a blast-cleaned, mild steel round bar with a brush. The coating was dried in the air and the steel samples were immersed in water collected from the open sea. Open circuit potential of steel was measured with silver/silver chloride reference electrode. The potential in seawater was in the range of — 740mV to — 956mV, indicating complete protection of steel against corrosion. This potential meets the criteria for protection as per clause 5.4.1 of Det Norsk Veritas Recommended Practice RPB 401 (1993), page 8.¹ The active coating system can be used for protecting the steel against corrosion in marine and any other highly corrosive environment. Accelerated tests in accordance with ASTM D5894 — 96² with freeze cycle developed by U.S. Federal Highway Administration are planned.     

三唑类农药的发展

本文论述了三唑类农药的进展，特别是在杀菌剂、杀虫剂和植物生长调节剂方面的开发动向。列表叙述了化学结构和生物活性。     

Optical Active Nano-Glass-Ceramics

This paper reviews the synthesis and characterization of several transparent glass-ceramics with optical active nanocrystals. Glass-ceramics containing ferroelectric Sr_xBa_1-xNb₂O₆ nanocrystals with an ellipsoidal shape show optical phase modulations in the presence of alternative electric fields. In the glass-ceramics with Ba₂TiSi₂O₈ (BTS) nanocrystals, BTS crystalline layers with a thickness of approximately 120 nm are formed at the surface and ellipsoidal-shaped crystallites with a diameter of 100–200 nm are dispersed in the glass matrix. Some TeO₂-based and GeO₂-based glasses show a prominent nanocrystallization. RE-doped CaF₂ nanocrystals are patterned in a spatially selected region by laser irradiations. The size, morphology, and dispersion state of nanocrystals should be carefully checked in each glass system and composition. The basic concept for the design of glass system and composition is also discussed. Some data on optical active performances in transparent glass-ceramics with nanocrystals were introduced.     

Reaction steady states and stationary states in modelling semi-batch enzyme hydrolysis

Dimensionless material balance equations describing an uninhibited enzyme hydrolysis process in a semi-batch reactor (i.e. fed-batch reactor) are formulated; numerical solution of these equations provided concentration profiles of the enzyme-substrate complex by using published kinetic parameters. The unrestricted values obtained are compared with estimates based separately on the reaction steady state and stationary state assumptions. Results are discussed in terms of the enzyme/substrate inventory used and it is found that the reaction steady state is a satisfactory approximation only when this ratio is sufficiently small. The stationary state may be a better approximation at other values, particularly when enzyme is added to substrate or when an empty tank is being filled. Reaction yields from semi-batch and batch operations are compared. Processing takes longer in the semi-batch operations and complete conversions are only practical in this mode when enzyme is added to substrate.     

活性阻隔树脂

M＆G集团公司生产出新型PET树脂,商品牌号为ActiTUF,用其生产出的单层容器产品具有主动或被动阻隔气体的性能。主动阻隔气体功能是利用一种专利的抑氧技术,而被动阻隔气体功能是根据使用要求,采用萘二甲酸酯或聚加成反应技术生产而成。与其他阻隔技术不同,这种     

Magnetoelectronic states of carbon toroids

Magnetoelectronic states of carbon toroids have been studied within the tight-binding model. These states are mainly determined by the magnitude and the direction of the magnetic field, and the toroid geometry (chiral angle, height, and radius). The magnetic field can make the angular momentum (L) along the longitudinal direction undergo both a large shift and strong coupling. This effect leads to the destruction of state degeneracy, the change of energy spacing, the alternation of quantization of wave function, the vanishing of periodic Aharonov-Bohm oscillations, and the semiconductor-metal transition (SMT). Armchair carbon toroids are quite different from zigzag carbon toroids in features such as state degeneracy, energy gap, existence of the SMT, and dependence on the magnetic field.     

Asymmetric steady states revisited

Alternative steady states of a multistable kinetic system can be attained at different locations along a catalytic surface. Propagation of resulting sharp concentration and/or temperature fronts leads to restoration of uniformity, unless special mechanisms come into action to preserve the emerging pattern. Two mechanisms leading to stabilization of asymmetric steady states are described here. The first one, called a global regulator, involves rapid pattern generation due to isothermal kinetics with forward inhibition or backward activation and freezing of propagating concentration fronts into steady inhomogeneities due to slow thermal interactions. Oscillatory solutions (swinging waves) with undulating motion of concentration fronts can be also generated this way. Another mechanism, called a landscape variegator, is based on modification of a catalyst under the influence of local reaction conditions corresponding to alternative homogeneous steady states which results in preservation of these states on stretches of the surface where they once have emerged.     

合成光学活性樟脑

本文研究了龙脑脱氢制光学活性樟脑,所用龙脑为天然产物或由α-蒎烯水合制得。脱氢反应在气相中进行,一种含锌固体作催化剂,收得率在95％以上。产物樟脑纯度高,并具有与原料几乎相同的光学纯度。     

头孢克肟活性酯(mica酯)的合成

头孢克肟（Cefixime）是第三代口服头孢菌素。我国已经将头孢克肟列入“九五”及2010年医药科技发展规划中．头孢克肟传统合成方法有以下两种：一种以7-ACA为原料,与水杨醛缩合后经过酯化、氯化等反应制得：另一种以脱乙酰头孢菌素C为原料,经过酰化、氯化等反应制得。这两种合成方法因技术路线长、成本高及三废污染问题影响了该产品的扩大生产。     

光学活性物质的工业生产方法

本文介绍了光学８活性牺牲垢几种工业规模的生产方法及最新的进展，分析了各种方法的特点及存在的问题。     

光学活性拟除虫菊酯的合成

<正> 天然除虫菊素的主要成分之一菊酸,是右旋反式(1R:3R)的立体构型。人工合成的除虫菊酸,若采用重氮乙酸乙酯对烯烃的加成环化反应,则产物是顺反异构体和外消旋体的四个异构体的混合物。用合成的方法获得与天然除虫菊素具有相同构型的菊酸,乃是近年来合成除虫菊研究的一个重要方向。马特塞(Ma-     

剩余活性污泥的利用

对污水生化处理过程中产生的剩余活性污泥进行厌氧消化、好氧消化,并将剩余活性污泥作为有机肥进行试验,使其在一定程度上得到综合利用。