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811.
Imai T Harano Y Kinoshita M Kovalenko A Hirata F 《The Journal of chemical physics》2007,126(22):225102
The free energy change associated with the coil-to-native structural transition of protein G in aqueous solution is calculated by using the molecular theory of solvation, also known as the three-dimensional reference interaction site model theory, to uncover the molecular mechanism of protein folding. The free energy is decomposed into the protein intramolecular energy, the hydration energy, and the hydration entropy. The folding is accompanied with a large gain in the protein intramolecular energy. However, it is almost canceled by the correspondingly large loss in the hydration energy due to the dehydration, resulting in the total energy gain about an order of magnitude smaller than might occur in vacuum. The hydration entropy gain is found to be a substantial driving force in protein folding. It is comparable with or even larger than the total energy gain. The total energy gain coupled with the hydration entropy gain is capable of suppressing the conformational entropy loss in the folding. Based on careful analysis of the theoretical results, the authors present a challenging physical picture of protein folding where the overall folding process is driven by the water entropy effect. 相似文献
812.
Nakamura R Hamada N Ichida H Tokunaga F Kanematsu Y 《Photochemistry and photobiology》2007,83(2):397-402
Pump-dump fluorescence spectroscopy was performed for photoactive yellow protein (PYP) at room temperature. The effect of the dump pulse on the population of the potential energy surface of the electronic excited state was examined as depletion in the stationary fluorescence intensity. The dynamic behavior of the population in the electronic excited state was successfully probed in the various combinations of the pump-dump delay, the dump-pulse wavelength, the dump-pulse energy and the observation wavelength. The experimental results were compared with the results obtained by the femtosecond time-resolved fluorescence spectroscopy. 相似文献
813.
We study operator log-convex functions on (0, ∞), and prove that a continuous nonnegative function on (0, ∞) is operator log-convex
if and only if it is operator monotone decreasing. Several equivalent conditions related to operator means are given for such
functions. Operator log-concave functions are also discussed. 相似文献
814.
815.
In this note, we prove a necessary and sufficient condition for whether a d-cyclic covering of the complex projective line has gonality 2 (i.e., is elliptic or hyperelliptic), where d is a positive integer. The case of 3 branch points has been solved in our previous paper (see [3]). 相似文献
816.
High-performance thin-layer chromatography (HPTLC) is a separation technique commonly used to identify and quantify compounds in chemical mixtures. Preliminary experiments indicated that Lichrospher silica gel 60 F254s HPTLC sheets were the most suitable for analyzing vitamin B12 compounds. This study revealed the advantages of miniaturized Lichrospher HPTLC for analyzing authentic vitamin B12 compounds as short migration distances (5 cm) and short development times (<45 min) in combination with high separation efficiency and sensitivity (>25 pmol at 254 nm). The practicability of using miniaturized HPTLC was demonstrated by the separation and identification of vitamin B12 compounds purified from foods using an immunoaffinity column. 相似文献
817.
Kazunari Naka Hirofumi Sato Akihiro Morita Fumio Hirata Shigeki Kato 《Theoretical chemistry accounts》1999,102(1-6):165-169
The free-energy profile for the Menshutkin-type reaction NH3 + CH3Cl → NH3CH3
+ + Cl− in aqueous solution is studied using the RISM-SCF method. The effect of electron correlation on the free-energy profile is
estimated by the RISM-MP2 method at the HF optimized geometries along the reaction coordinate. Solvation was found to have
a large influence on the vibrational frequencies at the reactant, transition state and product; these vibrational frequencies
are utilized to calculate the zero-point energy correction of the free-energy profile. The computed barrier height and reaction
exothermicity are in reasonable agreement with those of experiment and previous calculations. The change of solvation structure
along the reaction path is represented by radial distribution functions between solute-solvent atomic sites. The mechanisms
of the reaction are discussed from the view points of solute electronic and solvation structures.
Received: 26 June 1998/Accepted: 28 August 1998 / Published online: 2 November 1998 相似文献
818.
Ring‐opening polymerization of a seven‐membered cyclic carbonate, 1,3‐dioxepan‐2‐one, was investigated with a novel initiator system, BCl3‐HCl·Et2O. Addition of HCl·Et2O promoted the polymerization even at 0°C to produce the corresponding polycarbonate with controlled molecular weight and narrow polydispersity ratio (< 1.2). 相似文献
819.
Dry etching is an important tool to fabricate various semiconductor photonic devices. The roughness of etched sidewalls should be avoided as it reduces the scattering loss. We present a spatial frequency analysis of the sidewall roughness of dry etched facets processed by reactive ion etching. A characteristic parameter corresponding to a correlation length is estimated to be ∼0.5 μm. In addition, its effect on reflectivities of etched reflectors is discussed. 相似文献
820.
The radical ring‐opening polymerization (RROP) behavior of the following monomers is reviewed, and the possibility for application to functional materials is described: cyclic disulfide, bicyclobutane, vinylcyclopropane, vinylcyclobutane, vinyloxirane, vinylthiirane, 4‐methylene‐1,3‐dioxolane, cyclic ketene acetal, cyclic arylsulfide, cyclic α‐oxyacrylate, benzocyclobutene, o‐xylylene dimer, exo‐methylene‐substituted spiro orthocarbonate, exo‐methylene‐substituted spiro orthoester, and vinylcyclopropanone cyclic acetal. RROP is a promising candidate for producing a wide variety of environmentally friendly functional polymers. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 265–276, 2001 相似文献