title: Dynamic light scattering studies of irradiated kappa carrageenan.
abstract: Investigation of the dynamic behavior of irradiated kappa carrageenan (in KCl) as a function of irradiation dose and temperature was done by dynamic light scattering (DLS). The intensity correlation function (ICF) shifted towards shorter relaxation times with increasing radiation dose as a result of radiolysis. The characteristic decay time distribution function, G(gamma), indicates the presence of fast and slow mode peaks respectively at around 0.1-10 ms and 100-1000 ms. A peak broadening of the fast mode peak in G(gamma) appeared with decreasing temperature, indicating that coil-to-helical conformational transition took place. The conformation transition temperature (CTT) decreased with increasing radiation dose. No transition was observed for kappa-carrageenan irradiated at 200 kGy. A new faster relaxation mode appeared at around 0.1-1 ms at temperatures below the CTT. This peak is found in kappa-carrageenan irradiated at doses exclusively between 75 and 175 kGy. The peak height of this mode is largest at 100 kGy which corresponds to the optimum biologic activity of kappa-carrageenan reported previously.
authors.affiliation: Neutron Science Laboratory, Institute for Solid State Physics, University of Tokyo, Tokai, Ibaraki, Japan. abad@issp.u-tokyo.ac.jp, Ivabad@pnri.dost.gov.ph
authors.forename: L V
authors.initials: LV
authors.lastname: Abad
authors.forename: I R
authors.initials: IR
authors.lastname: Nasimova
authors.forename: L S
authors.initials: LS
authors.lastname: Relleve
authors.forename: C T
authors.initials: CT
authors.lastname: Aranilla
authors.forename: A M
authors.initials: AM
authors.lastname: De la Rosa
authors.forename: M
authors.initials: M
authors.lastname: Shibayama
mesh_terms: D002351:Carrageenan / Q000737:chemistry* / Q000494:pharmacology / Q000528:radiation effects*; D004307:Dose-Response Relationship, Radiation; D005782:Gels; D008027:Light; D008970:Molecular Weight; D012275:Oryza / Q000187:drug effects / Q000254:growth & development; D012542:Scattering, Radiation; D013997:Time Factors; D044366:Transition Temperature
chemical_list: D005782:Gels; D002351:Carrageenan