Molecular modeling for the interaction between proteasome beta 5 subunit and organotin compounds

It has been reported that organotins can inhibit the proteasomal chymotrypsin-like activity and induce cell death, but the interaction mode of organotins with proteasome has not been well defined. In this study, the IC₅₀ of butyltins and phenyltins against the proteasomal activity and the nature of their inhibition were investigated. It was found that both mono- and di-organotins were weak, reversible inhibitors against the proteasome, while tributyltin and triphenyltin were potent, irreversible proteasome inhibitors. In silico studies using the reversible organotin proteasome inhibitors demonstrated a tight correlation of the estimated proteasomal inhibition constants (Ki) with the experimental IC₅₀ values for proteasome inhibition. Furthermore, the Sn atom in TBT and TPT was found susceptible to form a coordinate bond with Thr 1 O^γ of the β5 subunit, which may account for the irreversible proteasome inhibition. The computational docking approach well predicted the inhibition nature of organotins toward the proteasomal chymotrypsin-like activity. This predictive model might aid in understanding the cytotoxic behavior of similar organometallic compounds.     

New implementations of MRCI in semiempirical frameworks

Multireference configuration interaction with single and double excitations (MRCISD) as well as its analytic CI gradients has been implemented in the semiempirical framework. The hole‐particle symmetry and a mixed driven model for computing coupling coefficients have been used in the new code that allows us to perform MRCI and gradient calculations with higher efficiency and less storage requirements. © 2010 Wiley Periodicals, Inc. J Comput Chem, 2010     

Encapsulation of polyaniline in 3-D interconnected mesopores of silica KIT-6

Composite material PANI/KIT-6, with polyaniline (PANI) chains encapsulated in the 3-D interconnected pore channels of mesoporous silica, KIT-6, has been synthesized via a gas-phase method. The composite formation and the presence of PANI inside the pore channels of KIT-6 were evidenced by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), small-angle X-ray scatter (SAXS), transmission electron microscopy (TEM), and N₂ adsorption–desorption isotherms. The PANI/KIT-6 composite showed good electrical conductivity (2.4 × 10^?3 S/cm) due to the formation of 3-D networks of PANI inside the 3-D interconnected channels of KIT-6. The resistance of PANI/KIT-6 composite at different relative humidities (RH) was investigated. An essentially linear relationship between the relative resistance of the composite and the relative humidity of the environment was found from 11.3% to 97.3% RH.     

铁苯基膦配合物均相催化乙酰丙酸乙酯与甲酸反应转化为γ-戊内酯的分子机制

本文基于密度泛函理论,计算了Fe(CF3SO3)2/PP3催化乙酰丙酸乙酯与甲酸反应转化为γ-戊内酯的反应机理。分析了单重态和三重态反应路径的热力学和动力学性质,结果表明除了预催化剂活化出现势能面交叉外,反应主要在三重态势能面上进行,包括以下几个步骤：甲酸盐配位方式重置,β-H消除得到活性催化剂[FeH(PP3)]+,接着乙酰丙酸乙酯的羰基碳和羰基氧接连被质子化得到中间体4-羟基戊酸乙酯,最后质子化的反离子CF3SO3H作为氢转移梭子协助分子内脱醇—关环生成目标产物γ-戊内酯。进一步探讨不同金属苯基膦配合物的催化活性,证实金属适宜的配位能力是筛选催化剂的关键。理论计算结果为优化设计高性能的生物质转化催化剂提供一定的理论指导。     

滴定分析的终点误差随待测物浓度及反应平衡常数单调变化之商榷

为了获得滴定分析的终点误差随待测物浓度、反应平衡常数这两个因素变化的准确规律,推导了有别于林邦终点误差公式的终点误差计算式,根据该式可以判断每个因素对计算结果的影响,结合在配位滴定分析和酸碱滴定分析的具体应用,结果发现：这两个因素其大小的变化不会一定导致终点误差绝对值的单调变化。     

The nonlinear refraction sign turned to reverse by intercalating cresyl violent dye into layered titanate nanosheets

Solid-state dye-doped materials are an attractive alternative to conventional liquid dye solution. In this study, the spectral characteristics of dye cresyl violet before and after intercalating into layered titanate nanosheets and forming a nanohybrid thin film were investigated by measuring absorption and fluorescence spectra. In addition, their nonlinear optical properties were studied using single beam z-scan technique under irradiation of low power continuous wave (CW) produced by DPSS laser with a wavelength of 532 nm. The nonlinear studying results reveal that the dye cresyl violet in solution has a negative nonlinear refractive index, but it reverses to positive after the dye is intercalated into layered titanate nanosheets with a negative nonlinear refractive index forming CV/HTO nanohybrid thin film. This method can provide a way to turn to reverse nonlinear refraction sign of the materials.     

激光相干合成中单元的相位和振幅波动对合成光束远场分布的影响

运用傅里叶光学分析法推导出系统抖动造成单个光源的相位和振幅发生波动时的远场光强表达式,以1维阵列为例分析了系统抖动对远场的影响.研究表明:随着参与合束的发光单元数目的增加,尖峰变锐,能量更集中;系统抖动引起了远场峰值光强的减少.出现了本底现象,破坏了远场的对称性和光束质量;激光阵列单个光源的相位随机抖动应该控制在3 π/8范围内;相干合束发光单元数目越多,系统抖动对远场的影响越小.     

Single-bunch emittance dilution in the perfect ILC main linac

In the ILC(International Linear Collider)main linac, low emittance preservation is the most important issue for beam dynamics study. As the main sources of emittance dilution, the dispersive and wakefield effects were studied in this paper. The theoretical calculations and numerical simulations of these two effects on single-bunch emittance dilution, without any misalignment errors, are presented in detail.     

赤铁矿和三羟铝石吸附Cu~(2+)的红外光谱研究

应用红外光谱法,研究了不同pH值和Cu2+浓度条件下,合成赤铁矿和三羟铝石吸附Cu2+后表面羟基结构及其特征吸收峰的变化。结果表明:(1)随Cu2+浓度增加,赤铁矿表面H—O—H和OH的变形振动参与了吸附反应,Cu2+强烈地缔结在Fe—O上,形成了Fe—O—(Cu)结构。(2)酸性条件下,H+破坏了赤铁矿表面的O—H结构,NO3-促使弱峰1 131 cm-1的产生。随pH值增大,赤铁矿表面OH-逐渐由伸缩振动转变为变形振动,Fe—OH和Fe3+—O2-结构不断发生改变。(3)三羟铝石对Cu2+的吸附发生在高波位,随Cu2+浓度增大,其表面游离羟基的O—H弯曲振动、水分子的OH-伸缩振动和H—O—H弯曲振动均参与了吸附反应,Al—O基中的Al3+渐被Cu2+取代从而加强了较低波位的振动强度。(4)随pH值增加,三羟铝石Al—OH的弯曲振动和Al—O的伸缩振动逐渐发生着改变,表明吸附Cu2+后,在其表面形成了AlOCu+与AlOCuOH结构。     

SiC晶体生长中流场的优化设计

物理气相输运法(PVT)是实验室最为常见的碳化硅(SiC)大块单晶生长方法.本文在碳化硅晶体生长模型化研究中,针对碳化硅单晶PVT生长过程中的传热传质等现象引入了对流传热中的场协同原理,利用这一原理对生长室内的流场温度场进行了优化,并对改良前后分别进行了数值模拟,研究了该原理对晶体生长的影响.实验室碳化硅单晶的生长成功...