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Abstract Resonance Raman spectroscopy was used to study the polyene-chain structure of carotenoids in light-harvesting pigment-protein complexes from purple photosynthetic bacteria. When major carotenoids of Rhodobacter sphaeroides were incorporated into the light-harvesting complexes of Chromatium vinosum , they showed a relatively intense Raman band at 965 cm-1 arising from the CH out-of-plane wagging modes of the polyene chain. This result was almost the same as that for the intrinsic carotenoids in Chromatium vinosum , but completely different from that for the intrinsic carotenoids in Rhodobacter sphaeroides . On the other hand, the intrinsic carotenoids of Chromatium vinosum lost the intensity of the 965 cm-1 Raman band upon protein denaturation. These results support the view that the intensity of the 965 cm-1 Raman band reflects distortion of the polyene chain, independent of its chemical structure. The polyene-chain distortion is affected by the apoprotein to which carotenoids are bound. The distortion of the polyene chain is correlated with a decrease in the efficiency of the energy transfer from carotenoids to bacteriochlorophyll. 相似文献
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NOZOMU KANNO HIROSHI TERASHIMA YU DAIMON NORIHIKO YOSHIKAWA MITSUO KOSHI 《国际化学动力学杂志》2014,46(8):489-499
The kinetics and mechanisms of H atom abstraction reactions from CH3NHNH2 by NO2 (R1) and related reactions have been investigated theoretically by using ωB97X‐D and CCSD(T)‐F12 quantum chemical calculations and the steady‐state unimolecular master equation analysis based on Rice–Ramsperger–Kassel–Marcus (RRKM) theory. For reaction (R1), both dissociation and isomerization steps between intermediate complexes were found to be important for the distribution of the dissociated bimolecular products. The dominant products of (R1) were found to be cis‐CH3NHNH and HONO at lower temperature. The branching ratios for CH3NNH2 formation paths increased with increasing temperature. On the same reaction potential energy surface, six reactions including isomerization reactions between CH3NNH2 and cis‐/trans‐CH3NHNH catalyzed by HONO were suggested to compete with the reverse reaction of (R1). The temperature‐ and pressure‐dependent rate expressions are proposed for kinetic modeling. 相似文献
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MASAE TAKAHASHI TAMÁS VESZPRÉMI KENKICHI SAKAMOTO MITSUO KIRA 《Molecular physics》2013,111(11):1703-1712
Mechanisms of four 1,2-addition reactions, H2Si=SiHMe + H2O, H2Si=SiHF + H2O, H2Si=SiH(C≡CH) + H2O, H2Si=SiH(NH2) + HF, were investigated in detail by the ab initio MO method using a recent approach combined with frontier MO theory. Twelve reaction pathways were found. The initial step of each reaction is the formation of a weakly bonded complex. According to the structure and the charge distribution of the complexes, the reactions are categorized into two types. Reactions starting from electrophilic interaction between the LUMO of water (or hydrogen fluoride) and the HOMO of disilene always result in syn-adducts. On the other hand, nucleophilic interaction between the HOMO of the water and the LUMO of disilene leads both syn and anti adducts. Depending on the acidity of the reagent and the charge on the silicon to be attacked, the reactions proceed in simple one-step mechanisms or in two-step ones via a Lewis-type complex. The paired interacting orbitals of the initial complexes were examined in order to predict the reaction pathways. 相似文献
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1,2-二乙炔基四苯基乙硅烷与1,2-二乙炔基四甲基乙硅烷在催化剂铑(Ⅰ)络合物[氯化三-(三苯基膦)铑]的作用下得到一种新的含硅共聚物。实验证明此共聚物的主链是有规交替结构。研究了固体薄膜及其溶液的光解作用,并测定了SbF5蒸气处理后的共聚物薄膜的导电性。 相似文献
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