This Article Full Text Full Text (PDF) Supplement All Versions of this Article: biophysj.106.096495v1 92/12/4369    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 HighWire Citing Articles via Google Scholar Google Scholar Articles by Abdulreda, M. H. Articles by Moy, V. T. Search for Related Content PubMed PubMed Citation Articles by Abdulreda, M. H. Articles by Moy, V. T.

Atomic Force Microscope Studies of the Fusion of Floating Lipid Bilayers

Department of Physiology & Biophysics, University of Miami Miller School of Medicine, Miami, Florida, USA

Correspondence: Address reprint requests to Vincent T. Moy, University of Miami Miller School of Medicine, Physiology & Biophysics Department, 1600 NW 10th Ave. Miami, FL 33136. Tel.: 305-243-3201; Fax: 305-243-5931; E-mail: vmoy{at}miami.edu.

This study investigated the fusion of apposing floating bilayers of egg L--phosphatidylcholine (egg PC) or 1,2-dimyristoyl-sn-glycero-3-phosphocholine. Atomic force microscope measurements of fusion forces under different compression rates were acquired to reveal the energy landscape of the fusion process under varied lipid composition and temperature. Between compression rates of 1000 and 100,000 pN/s, applied forces in the range from 100 to 500 pN resulted in fusion of floating bilayers. Our atomic force microscope measurements indicated that one main energy barrier dominated the fusion process. The acquired dynamic force spectra were fit with a simple model based on the transition state theory with the assumption that the fusion activation potential is linear. A significant shift in the energy landscape was observed when bilayer fluidity and composition were modified, respectively, by temperature and different cholesterol concentrations (15% chol 25%). Such modifications resulted in a more than twofold increase in the width of the fusion energy barrier for egg PC and 1,2-dimyristoyl-sn-glycero-3-phosphocholine floating bilayers. The addition of 25% cholesterol to egg PC bilayers increased the activation energy by 1.0 k_BT compared with that of bilayers with egg PC alone. These results reveal that widening of the energy barrier and consequently reduction in its slope facilitated membrane fusion.

This article has been cited by other articles:

				M. H. Abdulreda, A. Bhalla, E. R. Chapman, and V. T. Moy Atomic Force Microscope Spectroscopy Reveals a Hemifusion Intermediate during Soluble N-Ethylmaleimide-Sensitive Factor-Attachment Protein Receptors-Mediated Membrane Fusion Biophys. J., January 15, 2008; 94(2): 648 - 655. [Abstract] [Full Text] [PDF]