title: Diffusion coefficient and the secondary structure of poly-L-glutamic acid in aqueous solution.
abstract: The diffusion coefficients (D) of poly-L-glutamic acid (PLG) at various pHs are investigated by the laser-induced transient-grating method with a new photoreactive probe molecule. The pH dependence of D is compared with that of the helical content of PLG measured by circular dichroism. It is found that the pH dependences of both quantities are very similar. Since the frictions of the translational diffusion of charged and protonated carboxyl groups are found to be similar each other, it is concluded that the conformation of the main polymer chain is the main factor in determining the diffusion process; in other words, the alpha-helix conformation makes the molecular diffusion faster. This result indicates that the conformational change of a protein can be detected by monitoring the diffusion coefficient.
authors.affiliation: Department of Chemistry, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan.
authors.forename: Keiichi
authors.initials: K
authors.lastname: Inoue
authors.forename: Naoki
authors.initials: N
authors.lastname: Baden
authors.forename: Masahide
authors.initials: M
authors.lastname: Terazima
mesh_terms: D004058:Diffusion; D006863:Hydrogen-Ion Concentration; D007834:Lasers; D011099:Polyglutamic Acid / Q000737:chemistry* / Q000528:radiation effects; D017433:Protein Structure, Secondary; D012996:Solutions / Q000737:chemistry; D014867:Water / Q000737:chemistry
chemical_list: D012996:Solutions; D014867:Water; D011099:Polyglutamic Acid