This Article Full Text Full Text (PDF) All Versions of this Article: biophysj.106.097071v1 92/4/1306    most recent Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Howland, M. C. Articles by Parikh, A. N. Search for Related Content PubMed PubMed Citation Articles by Howland, M. C. Articles by Parikh, A. N.

Characterization of Physical Properties of Supported Phospholipid Membranes Using Imaging Ellipsometry at Optical Wavelengths

Michael C. Howland ^*, Alan W. Szmodis , Babak Sanii  and Atul N. Parikh  

^* Chemical Engineering and Materials Science, Biophysics, and Applied Science Graduate Groups, University of California, Davis, California 95616

Correspondence: Address reprint requests to A. N. Parikh, Biophysics and Applied Science Graduate Groups, University of California, Davis, CA 95616. Tel.: 530-754-7055; Fax: 530 752-2444; E-mail: anparikh{at}ucdavis.edu.

Subnanometer-scale vertical z-resolution coupled with large lateral area imaging, label-free, noncontact, and in situ advantages make the technique of optical imaging ellipsometry (IE) highly suitable for quantitative characterization of lipid bilayers supported on oxide substrates and submerged in aqueous phases. This article demonstrates the versatility of IE in quantitative characterization of structural and functional properties of supported phospholipid membranes using previously well-characterized examples. These include 1), a single-step determination of bilayer thickness to 0.2 nm accuracy and large-area lateral uniformity using photochemically patterned single 1,2-dimyristoyl-sn-glycero-3-phosphocholine bilayers; 2), hydration-induced spreading kinetics of single-fluid 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine bilayers to illustrate the in situ capability and image acquisition speed; 3), a large-area morphological characterization of phase-separating binary mixtures of 1,2-dilauroyl-sn-glycero-3-phosphocholine and galactosylceramide; and 4), binding of cholera-toxin B subunits to GM₁-incorporating bilayers. Additional insights derived from these ellipsometric measurements are also discussed for each of these applications. Agreement with previous studies confirms that IE provides a simple and convenient tool for a routine, quantitative characterization of these membrane properties. Our results also suggest that IE complements more widely used fluorescence and scanning probe microscopies by combining large-area measurements with high vertical resolution without the use of labeled lipids.