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991.
Pang Xiao-feng Zhang Huai-Wu 《International Journal of Infrared and Millimeter Waves》2006,27(5):735-752
The mechanism and properties of infrared absorption of α-helix protein molecules are studied by a theory of bio-energy transport
established on the basis of molecular structure. From the vibrational energy-spectra of molecules obtained from this theory
we know that the infrared lights with wavelengths of 2 μm −7 μm can be absorbed by α-helix protein molecules. This is basically
consistent with experimental data of infrared absorption of collagen and hemoglobin and bivine serum albumen (BSA) proteins
with α-helix structure. From these results we account further for the mechanism and properties of biological effect of infrared
lights absorbed by the living systems, i.e., the energy of infrared lights is directly absorbed by the amide-Is in amino acid
residues in the protein molecules, which results in vibration of amide-1 and change of conformation of proteins and transport
of bio-energy from one place to other along the protein molecular chains in human beings and animals. This is a kind of non-thermally
biological effect. 相似文献
992.
Fluorescence resonance energy transfer (FRET) is a popular tool to study equilibrium and dynamical properties of polymers
and biopolymers in condensed phases and is now widely used in conjunction with single molecule spectroscopy. In the data analysis,
one usually employs the F?rster expression which predicts (l/R
6) distance dependence of the energy transfer rate. However, critical analysis shows that this expression can be of rather limited validity in many cases. We demonstrate this by explicitly considering a donor-acceptor system,
polyfluorene (PF6)-tetraphenylporphyrin (TPP), where the size of both donor and acceptor is comparable to the distance separating them. In
such cases, one may expect much weaker distance (as l/R
2 or even weaker) dependence. We have also considered the case of energy transfer from a dye to a nanoparticle. Here we find
l/R
4 distance dependence at large separations, completely different from F?rster. We also discuss recent application of FRET to
study polymer conformational dynamics.
Dedicated to Prof J Gopalakrishnan on his 62nd birthday. 相似文献
993.
Feng‐Ling Liu Ling Peng Jian‐Xia Zhao Shou‐Qing Wang 《International journal of quantum chemistry》2005,103(2):167-175
Structures, energies, and vibrational frequencies have been calculated for two C50H40 isomers with three dodecahedrane cages sharing two pentagons at the B3LYP/6‐31G* level of theory. Thus, two C50H40 isomers have the form of coplanar tri‐dodecahedrane‐cage molecules. The symmetry of one isomer is D5d and that of another is C2V. Heats of formation and vertical ionization energies for two C50H40 isomers have been estimated in this study. Heats of formation as well as vibrational analysis indicate that two C50H40 isomers enjoy sufficient stability to allow for its experimental preparation. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005 相似文献
994.
Fumihiko Tanaka 《Journal of Polymer Science.Polymer Physics》2003,41(20):2405-2412
Number‐ and weight‐average molecular weight of condensation polymers formed by primary molecules carrying different species of functional groups {Ai} (i = 1, 2, …, s) are derived by cascade theory. These functional groups are allowed to form multiple junctions of variable multiplicity k. The gel point condition is found to be given by ∑ wi/|μw,i + 1/∑ fi ? 1 = 0, where fi is the number of Ai groups specified by the index i on a primary molecule, wi ≡ fi/∑ fi the number fraction of the species i it carries, and |μw,i the weight average multiplicity of the junctions formed by the groups Ai. The explicit form of the molecular weight distribution function is found for the simplest case of two components. Possible application to thermoreversible gelation is suggested. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 2405–2412, 2003 相似文献
995.
It has been proved by ab initio calculation and theoretical analysis that there exist [N2]2--N2 molecular dimers with D2h symmetry group, and there also exists an electric dipole excimer-like transition a1B2g→a1B3u. The theoretical spectra accord with the experimental results for transition a1B2g→a1B3u. The stimulated emission characteristic of N2 molecular dimer was researched through the microwave excited highly pure nitrogen and the method of amplified spontaneous emission. The experimental results show that N2 molecular dimer has stimulated emission characteristics when the microwave power is more than 100 W and the N2 pressure is in the range from 260 Pa to 2200 Pa. 相似文献
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