A theoretical study on oligopeptide chains of glycine-alanine by density functional theory（DFT） is given in this paper. Raman spectra of the oligopeptide chains are examined. The geometric structures, frontier orbit...A theoretical study on oligopeptide chains of glycine-alanine by density functional theory（DFT） is given in this paper. Raman spectra of the oligopeptide chains are examined. The geometric structures, frontier orbital, energy gap, atomic charge distribution, density of states and chemical activity of the side chain are studied at the B3LYP/6-31G（d） level. Results show that, with the number of residues increasing, vibrations of typical functional groups present Raman frequency shift, and the energy gap is gradually reduced. The HOMO and LUMO focus on the amino and carboxyl at the ends of oligopeptides. It is helpful for oligopeptides to self-assemble into chains. In addition, different residues（glycine or alanine） at the ends of chains result in the even-odd effect of orbital energy in the growth process. The size effects of physical and chemical properties only exist when the oligopeptides are shorter, and the phenomenon disappeared as the chain continues to grow.展开更多
The effects of the concentration of sodium chloride in an aqueous solution（cNacl and the temperature on the molecular size of poly（sulfobetaine methacrylate）（PSBMA） were studied via viscometry and dynamic light s...The effects of the concentration of sodium chloride in an aqueous solution（cNacl and the temperature on the molecular size of poly（sulfobetaine methacrylate）（PSBMA） were studied via viscometry and dynamic light scattering（DLS）. The morphology of single-chain PSBMA was determined by atomic force microscopy（AFM）. The results demonstrate that the hydrodynamic diameter of PSBMA can be expressed as a continuous function of CNaCl, with the molecular size of PSBMA increasing and eventually approaching an asymptotic value with increasing CNaCl. The molecular size of PSBMA at a lower CNaCI（0.04 mol/L） increases with increasing temperature, which is the opposite of the temperature effect at a higher CNaCl（2.0 mol/L）. Therefore, the internal structure of PSBMA chains in solutions with a low salt concentration differs from that in solutions with a high salt concentration. In addition, the morphology of single chains of PSBMA appears to be spherical, containing 89% void space, and the apparent size of the dried chains is almost identical to that in solution.展开更多
基金Supported by the National Natural Science Foundation of China(No.60878063)the Program from Traditional Chinese Medicine Bureau of Guangdong Province(No.2008233)
文摘A theoretical study on oligopeptide chains of glycine-alanine by density functional theory（DFT） is given in this paper. Raman spectra of the oligopeptide chains are examined. The geometric structures, frontier orbital, energy gap, atomic charge distribution, density of states and chemical activity of the side chain are studied at the B3LYP/6-31G（d） level. Results show that, with the number of residues increasing, vibrations of typical functional groups present Raman frequency shift, and the energy gap is gradually reduced. The HOMO and LUMO focus on the amino and carboxyl at the ends of oligopeptides. It is helpful for oligopeptides to self-assemble into chains. In addition, different residues（glycine or alanine） at the ends of chains result in the even-odd effect of orbital energy in the growth process. The size effects of physical and chemical properties only exist when the oligopeptides are shorter, and the phenomenon disappeared as the chain continues to grow.
基金Supported by the National Natural Science Foundation of China（No.21174053）.
文摘The effects of the concentration of sodium chloride in an aqueous solution（cNacl and the temperature on the molecular size of poly（sulfobetaine methacrylate）（PSBMA） were studied via viscometry and dynamic light scattering（DLS）. The morphology of single-chain PSBMA was determined by atomic force microscopy（AFM）. The results demonstrate that the hydrodynamic diameter of PSBMA can be expressed as a continuous function of CNaCl, with the molecular size of PSBMA increasing and eventually approaching an asymptotic value with increasing CNaCl. The molecular size of PSBMA at a lower CNaCI（0.04 mol/L） increases with increasing temperature, which is the opposite of the temperature effect at a higher CNaCl（2.0 mol/L）. Therefore, the internal structure of PSBMA chains in solutions with a low salt concentration differs from that in solutions with a high salt concentration. In addition, the morphology of single chains of PSBMA appears to be spherical, containing 89% void space, and the apparent size of the dried chains is almost identical to that in solution.
