Molecular dynamics study of bipolar tetraether lipid membranes

¹ National Institute of Advanced Industrial Science and Technology

^* To whom correspondence should be addressed. E-mail: w.shinoda{at}aist.go.jp.

Submitted on February 8, 2005
Revised on March 14, 2005
Accepted on 1 August 2005

	Abstract

Membranes composed of bipolar tetraether lipids have been studied by a series of 25ns-molecular dynamics simulations to understand the microscopic structure and dynamics as well as membrane area elasticity. By comparing macrocyclic and acyclic tetraether and diether archaeal lipids, the effect of tail linkage of the two phytanyl chained lipids on the membrane properties is elucidated. Tetraether lipids show smaller molecular area and lateral mobility. For the latter, calculated diffusion coefficients are indeed one order of magnitude smaller than that of the diether lipid. The two tetraether membranes are alike in many physical properties except for membrane area elasticity. The macrocyclic tetraether membrane shows higher elastic area expansion modulus than its acyclic counterpart by a factor of three. Free energy profiles of a water molecule crossing the membranes show no major difference in barrier height, while a significant difference is observed near the membrane center due to the lack of the slip plane in tetraether membranes.

Key Words: Archaeal lipid, Dynamics, Free energy calculation, Molecular dynamics simulation, Tetraether lipid, membrane area elasticity

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