Energetics of water permeation through fullerene membrane

doi:10.1073/pnas.0705010104

Energetics of water permeation through fullerene membrane

*Department of Chemistry, University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan;
^¶Exploratory Research for Advanced Technology, Japan Science and Technology Agency, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan

Edited by David A. Tirrell, California Institute of Technology, Pasadena, CA, and approved July 23, 2007 (received for review May 28, 2007)

Abstract

Lipid bilayer membranes are important as fundamental structures in biology and possess characteristic water-permeability, stability, and mechanical properties. Water permeation through a lipid bilayer membrane occurs readily, and more readily at higher temperature, which is largely due to an enthalpy cost of the liquid-to-gas phase transition of water. A fullerene bilayer membrane formed by dissolution of a water-soluble fullerene, Ph₅C₆₀K, has now been shown to possess properties entirely different from those of the lipid membranes. The fullerene membrane is several orders of magnitude less permeable to water than a lipid membrane, and the permeability decreases at higher temperature. Water permeation is burdened by a very large entropy loss and may be favored slightly by an enthalpy gain, which is contrary to the energetics observed for the lipid membrane. We ascribe this energetics to favorable interactions of water molecules to the surface of the fullerene molecules as they pass through the clefts of the rigid fullerene bilayer. The findings provide possibilities of membrane design in science and technology.

Footnotes

^§To whom correspondence may be addressed. E-mail: isobe{at}mail.tains.tohoku.ac.jpor nakamura{at}chem.s.u-tokyo.ac.jp
Author contributions: H.I. and E.N. designed research; T.H. performed research; H.I., T.H., and E.N. analyzed data; and H.I. and E.N. wrote the paper.
↵ ^†Present address: Department of Chemistry, Tohoku University, Aoba-ku, Sendai 980-8578, Japan.
The authors declare no conflict of interest.
This article is a PNAS Direct Submission.
This article contains supporting information online at www.pnas.org/cgi/content/full/0705010104/DC1.
Abbreviation:

THF,

tetrahydrofuran.
Freely available online through the PNAS open access option.