9513669 Chong This research is to study physical properties of liposomes composed of the tetraether polar lipid fraction E (PLFE) isolated from thermoacidophilic archaebacteria Sulfolobus acidocaldarius. The specific aims are to determine isothermal compressibility, thermal expansivity, proton permeability, lipid rotational and lateral diffusion of PLFE liposomes. The hypotheses are: (i) PLFE liposomes are rigid but loosely packed and (ii) the sugar moieties at the PLFE polar headgroups play a crucial role for maintaining a pH gradient across the archaebacterial plasma membrane. Fluorescence probe techniques as well as chemical modifications and high pressure methodologies will be employed. %%% The general purpose of this research is to gain a better understanding of the structure-function relationship of the archaebacterial membrane. The results obtained in this research will set a solid basis for the future studies of interactions between Sulfolobus acidocaldarius membrane-bound proteins and PLFE lipids. Archaebacteria are curios and remarkable organisms. The native habitat of the thermoacidophilic archaebacterium Sulfolobus acidocaldarius is hot (65-75 0C) and acidic (pH 2-3) sulfur springs. Besides, Sulfolobus has found wide use in biotechnology, most notably in the use of its DNA polymerase and (-galactosidase for molecular biology research. Also, liposomes made from archaebacteria-type lipids show remarkable thermostability, which may have potential use in the nanoscale design of artificial ion channels and membrane receptors. ***
