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Atomic Force Microscopy Studies of Functional and Dysfunctional Pulmonary Surfactant Films. I. Micro- and Nanostructures of Functional Pulmonary Surfactant Films and the Effect of SP-A

Yi Y. Zuo ^*  , Eleonora Keating ^*, Lin Zhao , Seyed M. Tadayyon ^*, Ruud A. W. Veldhuizen , Nils O. Petersen ^*  ¶ and Fred Possmayer  

^* Department of Chemistry, Department of Biochemistry, Department of Obstetrics and Gynaecology, Departments of Physiology and Pharmacology and Medicine, University of Western Ontario, London, Ontario, Canada; and ^¶ National Institute for Nanotechnology, National Research Council Canada, Edmonton, Alberta, Canada

Correspondence: Address reprint requests to Fred Possmayer, Depts. of Obstetrics/Gynaecology and Biochemistry, The University of Western Ontario Schulich School of Medicine and Dentistry, Dental Sciences Building 5009, London, Ontario, Canada N6A 5C1. Tel.: 519-661-2111, ext. 80972; Fax: 519-661-3175; E-mail: fpossmay{at}uwo.ca.

Monolayers of a functional pulmonary surfactant (PS) can reach very low surface tensions well below their equilibrium value. The mechanism by which PS monolayers reach such low surface tensions and maintain film stability remains unknown. As shown previously by fluorescence microscopy, phospholipid phase transition and separation seem to be important for the normal biophysical properties of PS. This work studied phospholipid phase transitions and separations in monolayers of bovine lipid extract surfactant using atomic force microscopy. Atomic force microscopy showed phospholipid phase separation on film compression and a monolayer-to-multilayer transition at surface pressure 40–50 mN/m. The tilted-condensed phase consisted of domains not only on the micrometer scale, as detected previously by fluorescence microscopy, but also on the nanometer scale, which is below the resolution limits of conventional optical methods. The nanodomains were embedded uniformly within the liquid-expanded phase. On compression, the microdomains broke up into nanodomains, thereby appearing to contribute to tilted-condensed and liquid-expanded phase remixing. Addition of surfactant protein A altered primarily the nanodomains and promoted the formation of multilayers. We conclude that the nanodomains play a predominant role in affecting the biophysical properties of PS monolayers and the monolayer-to-multilayer transition.

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				Y. Y. Zuo, S. M. Tadayyon, E. Keating, L. Zhao, R. A. W. Veldhuizen, N. O. Petersen, M. W. Amrein, and F. Possmayer Atomic Force Microscopy Studies of Functional and Dysfunctional Pulmonary Surfactant Films, II: Albumin-Inhibited Pulmonary Surfactant Films and the Effect of SP-A Biophys. J., September 15, 2008; 95(6): 2779 - 2791. [Abstract] [Full Text] [PDF]