Calculation of the Free Energy Profile of H2O, O2, CO, CO2, NO, and CHCl3 in a Lipid Bilayer with a Cavity Insertion Variant of the Widom Method
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- 作者：Pá ; l Jedlovszky and Mihaly Mezei
- 刊名：Journal of the American Chemical Society
- 出版年：2000
- 出版时间：May 31, 2000
- 年：2000
- 卷：122
- 期：21
- 页码：5125 - 5131
- 全文大小：135K
- 年卷期：v.122,no.21(May 31, 2000)
- ISSN：1520-5126
文摘
The excess free energy profile of H2O, O2, CO, CO2, NO, and CHCl3 has been computed across afully hydrated dimyristoylphosphatidylcholine (DMPC) bilayer by a cavity insertion variant of the Widomtest particle method. This Cavity Insertion Widom (CIW) method modifies the original Widom procedure insuch a way that, analogously to the cavity biased particle insertions used in grand canonical and Gibbs ensembleMonte Carlo simulations, it inserts the test particle into cavities of suitable radius only. Results on aqueoussystems show that this modification can make the Widom method considerably faster and also more accurate.The free energy profiles obtained are in accordance with the physiological properties of the investigatedmolecules. It is found that the interior of the membrane constitutes a free energy barrier of about 13 kcal/molfor H2O, and a free energy well of 3-4 kcal/mol for O2, CO, and NO. In contrast to these four free energyprofiles, which change monotonically between the two phases of the membrane, the free energy profile ofCO2 has about 4 kcal/mol deep wells in the two interfacial regions. While, due to its larger size, the results forCHCl3 are considerably less accurate than for the other five solutes it could still be concluded that its excessfree energy is a few kilocalories per mole lower in the interior of the membrane than in the aqueous phase,and the headgroup regions constitute large free energy barriers.