FLUORESCENCE ENERGY TRANSFER BETWEEN DIMETHYLDIAZAPEROPYRENIUM DICATION AND ETHIDIUM INTERCALATED IN POLY d(A-T)

Dimethyldiazaperopyrenium is one of the largest known DNA intercalators. Fluorescence energy transfer occurred between dimethyldiazaperopyrenium (donor) and ethidium (acceptor) when these dyes were bound to a double-stranded polynucleotide such as poly d(A-T). The addition of increasing amounts of ethidium bromide led to a marked shortening of the fluorescence lifetime of the donor, whereas the excited state of the acceptor was progressively populated via energy transfer from the donor. Critical Förster distance between these two chromophores was calculated to be 3.8 nm. The observed transfer efficiency was lower than that calculated on the basis of this critical distance and a statistical distribution of bound drugs. These results are discussed taking into account the conformational change induced by intercalation of dimethyldiazaperopyrenium in the double-stranded polynucleotide.     

PHOTODYNAMIC INHIBITION OF ESCHERICHIA COLI DNA POLYMERASE I BY 8-METHOXYPSORALEN PLUS NEAR ULTRAVIOLET IRRADIATION

Abstract— Morphological abnormality due to the UV irradiation of sperm and its modification by photoreactivation (PR) were studied in the sea urchin, Hemicentrotus pukherrimus. When sperm was UV-irradiated and allowed to fertilize unirradiated eggs, the effect of the UV was manifested as an abnormal morphology of embryos in the gastrula or later stages. The UV-induced morphological abnormality was prevented by photoreactivation when the fertilized eggs were illuminated with visible light. In the experiments on a stage-dependent change of PR effectiveness, it was found that an illumination sufficed to effect a nearly complete PR when applied up to the onset of the first DNA synthetic phase, while the PR effectiveness declined thereafter. Illumination after the completion of DNA synthesis had little effect for PR.     

多约束水平运输问题的时间费用均衡

基于为顾客提供最佳服务的现代营销理念,剖析了从一定产地到一定销地所发生的运输问题,构建了时间用均衡的目标模式及多目标约束水平MC^2运输问题的数学模型,本文在建立一系列定义,定理的基础上,提出了认明时间费用均衡解空间的优化决策方法,并结合示例展现了这一方法在解决客观实际问题中的有效性。     

Comparison of α CH and CF activation in alkyl transition metal complexes: a DFT and CASSCF study

DFT (B3PW91) and CASSCF calculations have been carried out to study the relative α migratory abilities of H and F in alkyl transition metal complexes. It is shown that the activation energy is considerably lower to migrate H than F, whereas the energies of reaction are similar for the two reactions. A study of the electron configurations and the orbitals describing these configurations shows that the high activation energy for F is due to a 4-electron repulsion between an F lone pair and the occupied Ru=C π orbital.