title: Density fluctuations and rotational isomerization in phospholipid bilayers as studied by ultrasonic absorption spectroscopy.
abstract: Broadband ultrasonic absorption spectra are discussed for some aqueous solutions of single-walled phospholipid bilayer vesicles. It is shown that the excess absorption found with all samples can be represented by a sum of a Debye-type relaxation term with discrete relaxation time and a Fixman-Kawasaki term. The former term reflects the kinetics of structural isomerization of the hydrocarbon chains. The values of its relaxation time (0.09-0.56 ns) agree with those for pure n-alkanes of comparable length. The latter terms seems to be due to density fluctuations in the hydrocarbon part of the double layer. Fluctuation correlation lengths between 1 and 30 A result from the analysis of the ultrasonic spectra.
authors.affiliation: Drittes Physikalisches Institut, Universität Göttingen, Germany.
authors.forename: U
authors.initials: U
authors.lastname: Kaatze
authors.forename: M
authors.initials: M
authors.lastname: Brai
mesh_terms: D055598:Chemical Phenomena; D002627:Chemistry, Physical; D007536:Isomerism; D008051:Lipid Bilayers / Q000737:chemistry*; D008954:Models, Biological; D010743:Phospholipids / Q000737:chemistry*; D013057:Spectrum Analysis / Q000379:methods; D014465:Ultrasonics
chemical_list: D008051:Lipid Bilayers; D010743:Phospholipids