title: Direct imaging of domains in the Lbeta' state of 1,2-dipalmitoylphosphatidylcholine bilayers.
abstract: A near-field scanning optical microscope was used to study domain formation and evolution in single-component supported lipid bilayers in the gel (L(beta') state. Results on 1,2-dipalmitoylphosphatidylcholine (DPPC) bilayers on glass substrates at room temperature are presented. The domain structure is determined by means of the optical anisotropy of the sample, which arises because DPPC molecules are tilted at theta approximately 32 degrees with respect to the bilayer normal [J. F. Nagle and S. Tristram-Nagle, Biochim. Biophys. Acta 1469, 159 (2000)]. From the measurements we obtain the difference in the index of refraction for the directions parallel and perpendicular to the acyl chains of the lipid molecules, Delta(n)=0.37+/-0.12, in good agreement with calculated and measured values. Direct evidence of the existence of domains in the L(beta') state is provided. These domains, defined as the correlation of the tilt angle theta, are found to be 1-2 microm across. Furthermore, it was found that they are robust under single-lipid-molecule diffusion, remaining unchanged over periods of hundreds of minutes.
authors.affiliation: Department of Physics, Indiana University-Purdue University Indianapolis, 402 North Blackford Street, Building LD154, Indianapolis, Indiana 46202, USA.
authors.forename: C-W
authors.initials: CW
authors.lastname: Lee
authors.forename: R S
authors.initials: RS
authors.lastname: Decca
authors.forename: S R
authors.initials: SR
authors.lastname: Wassall
authors.forename: J J
authors.initials: JJ
authors.lastname: Breen
mesh_terms: D015060:1,2-Dipalmitoylphosphatidylcholine / Q000737:chemistry*; D000465:Algorithms; D020087:Alu Elements; D001703:Biophysics / Q000379:methods*; D002890:Chromosomes, Human, Pair 20; D002891:Chromosomes, Human, Pair 21; D002892:Chromosomes, Human, Pair 22; D004247:DNA / Q000737:chemistry; D004058:Diffusion; D005583:Fourier Analysis; D006801:Humans; D008051:Lipid Bilayers / Q000737:chemistry*; D008055:Lipids / Q000737:chemistry; D018625:Microscopy, Atomic Force; D015233:Models, Statistical; D008962:Models, Theoretical; D009690:Nucleic Acid Conformation; D010743:Phospholipids / Q000737:chemistry; D011108:Polymers; D017434:Protein Structure, Tertiary; D017422:Sequence Analysis, DNA; D013499:Surface Properties; D013501:Surface-Active Agents / Q000737:chemistry*
chemical_list: D008051:Lipid Bilayers; D008055:Lipids; D010743:Phospholipids; D011108:Polymers; D013501:Surface-Active Agents; D015060:1,2-Dipalmitoylphosphatidylcholine; D004247:DNA