Physical Properties of Archaeal Tetraether Lipid Membranes As Revealed by Differential Scanning and Pressure Perturbation Calorimetry, Molecular Acoustics, and Neutron Reflectometry: Effects of Pressu

详细信息    查看全文

• 作者：Yong Zhai ; Parkson Lee-Gau Chong ; Leeandrew Jacques-Asa Taylor ; Mirko Erlkamp ; Sebastian Grobelny ; Claus Czeslik ; Erik Watkins ; Roland Winter
• 刊名：Langmuir
• 出版年：2012
• 出版时间：March 20, 2012
• 年：2012
• 卷：28
• 期：11
• 页码：5211-5217
• 全文大小：349K
• 年卷期：v.28,no.11(March 20, 2012)
• ISSN：1520-5827

文摘

The polar lipid fraction E (PLFE) is a major tetraether lipid component in the thermoacidophilic archaeon Sulfolobus acidocaldarius. Using differential scanning and pressure perturbation calorimetry as well as ultrasound velocity and density measurements, we have determined the compressibilities and volume fluctuations of PLFE liposomes derived from different cell growth temperatures (T_g = 68, 76, and 81 掳C). The compressibility and volume fluctuation values of PLFE liposomes, which are substantially less than those detected from diester lipid membranes (e.g., DPPC), exhibit small but significant differences with T_g. Among the three T_gs employed, 76 掳C leads to the least compressible and most tightly packed PLFE membranes. This temperature is within the range for optimal cell growth (75鈥?0 掳C). It is known that a decrease in T_g decreases the number of cyclopentane rings in archael tetraether lipids. Thus, our data enable us to present the new view that membrane packing in PLFE liposomes varies with the number of cyclopentane rings in a nonlinear manner, reaching maximal tightness when the tetraether lipids are derived from cells grown at optimal T_gs. In addition, we have studied the effects of pressure on total layer thickness, d, and neutron scattering length density, 蟻_n, of a silicon鈥揇₂O interface that is covered with a PLFE membrane using neutron reflectometry (NR). At 55 掳C, d and 蟻_n are found to be rather insensitive to pressure up to 1800 bar, suggesting minor changes of the thickness of the membrane鈥檚 hydrophobic core and headgroup orientation upon compression only.