[gmx-users] Re: Measure contour area of bilayer undulation

[Pedro Alexandre de Araújo Gomes Lapido Loureiro]

Hi,



>
>
> My point was rather the opposite - when people measure area/lipid in the
> lab on bilayer slabs there will be undulations present since they are
> typically not under tension. We discussed this with John Nagle a couple of
> years ago, and came to the conclusion that you should not try to compensate
> for it. This is one of the reasons you get more accurate results for larger
> systems.
>

I'm afraid this is an oversimplification of the problem. In order to obtain
an accurate electron density profile of the membrane you need at least 3
to 4 orders of X-ray diffraction. For this, it is needed a non-zero tension
by means of an applied osmotic pressure. The tension-free state is
extrapolated from an osmotic pressure curve.
I think Hwankyu is right in his questioning. Maybe a better approach is to
simulate the membrane system in a constant area ensemble in several values
of average area per lipid. You can, then, compare your simulated
structures with the experimental one and choose the "better" one. This is
not my idea. It has been done before in the same Nagle group.

Regards.

Pedro.
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