title: Temperature dependent intermediate structures during the main phase transition of dimyristoyl phosphatidylcholine vesicles a combined iodine laser-temperature jump and time resolved cryo-electron microscopy study.
abstract: The kinetics of the main phase transition of dimyristoylphosphatidyl choline (DMPC) unilamellar vesicles were investigated in the time range from microseconds to seconds. Iodine laser-temperature jump (ILTJ) experiments showed three discrete relaxation phenomena. Time resolved cryo-electron microscopy (CEM) was applied to produce images of intermediate states typical for the relaxation times of lipid vesicles in the micro- to millisecond time window. A careful measurement of the rate of temperature decrease observed during the production of vitrified lamellae of aqueous samples on a copper grid was performed. The best conditions resulted in average rates of cooling of 3 x 10(4) K/s. By comparing the images from CEM of DMPC vesicle samples vitrified above, at, and below the phase transition temperature a structural model was designed, which explains the temperature jump relaxation times in the micro- to millisecond time range by the formation and disappearance of coexisting clusters of crystalline, intermediate, and fluid lipid areas inside the DMPC bilayers.
authors.affiliation: Fritz-Haber-Institut der Max-Planck-Gesellschaft, D-14195 Berlin-Dahlem, Germany.
authors.forename: R
authors.initials: R
authors.lastname: Groll
authors.forename: A
authors.initials: A
authors.lastname: Böttcher
authors.forename: J
authors.initials: J
authors.lastname: Jäger
authors.forename: J F
authors.initials: JF
authors.lastname: Holzwarth