A Molecular Dynamics Study of the Response of Lipid Bilayers and Monolayers to Trehalose

¹ Food and Drug Adminstration
² Food and Drug Administration

^* To whom correspondence should be addressed. E-mail: pastor{at}cber.fda.gov.

Submitted on May 5, 2005
Revised on June 19, 2005
Accepted on 15 September 2005

	Abstract

Surface tensions evaluated from molecular dynamics simulations of fully hydrated DPPC bilayers and monolayers at surface areas/lipid of 54, 64 and 80 Å2 are uniformly lowered 4-8 dyn/cm upon addition of trehalose in a 1:2 trehalose:lipid ratio. Constant surface tension simulations of bilayers yield the complementary result: an increase in surface area consistent with the surface pressure-surface area (-A) isotherms. Hydrogen bonding by trehalose, replacement of waters in the headgroup region, and modulation of the dipole potential are all similar in bilayers and monolayers at the same surface area. These results strongly support the assumption that experimental measurements on the interactions of surface active components such as trehalose with monolayers can yield quantitative insight to their effects on bilayers. The simulations also indicate that the 20-30 dyn/cm difference in surface tension of the bilayer leaflet and monolayer arises from differences in the chain regions, not the headgroup/water interfaces.

Key Words: DPPC, equivalence of ensembles, isotherm-area isotherm, membrane dipole potential, molecular dynamics simulation, water replacement

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