# [gmx-users] [Fwd: questions about surface tension]

David van der Spoel spoel at xray.bmc.uu.se
Thu Jul 17 15:47:02 CEST 2008


-------- Original Message --------
Date: Thu, 17 Jul 2008 21:27:28 +0800
From: Li Yang <liyang1980_0_0 at 163.com>
To: David van der Spoel <spoel at xray.bmc.uu.se>

Dir Sir

I must apologize if I've disturbed you.

I have been learning the molecular dynamics simulation. And now，I'm
interesting at the surface tension calculations.  	I have some questions

1. For the formula, \gamma_m=(P_N - P_L) * L_z / 2, is it only
available for a flat surface, like a lipid bilayer in water ?  For
example, the surface fluctuation of lipid bilayer often occur in the
simulation, sometimes, the surface is not flat but bending, in such a
case, is the formula still available?     What about the vesicle?

2. In my system, there are a bilayer patch and a NP of ~10nm, they are
all in water. At the beginning (state 1), NP and the bilayer don't
contact each other. After some nanoseconds runtime, NP adsorbs on the
surface of the bilayer (state 2). Finally(state 3), the NP embeds into
the inner of the lipid bilayer.

In this case, how can I measure the changing surface tension of the
LIPID BILAYER during the simulation?  Is the formula above available for
my system?
In state 1, is that meaning there are four interface in the system? What
about the case (state 2,3) that the NP contacting the bilayer ?

I hope I've describe my questions clearly. Any suggestion or recommended
reference will be appreciated.

Sincerely

Li Yang

Li Yang
liyang1980_0_0 at 163.com
2008-07-17

--
David van der Spoel, Ph.D., Professor of Biology
Molec. Biophys. group, Dept. of Cell & Molec. Biol., Uppsala University.
Box 596, 75124 Uppsala, Sweden. Phone:	+46184714205. Fax: +4618511755.
spoel at xray.bmc.uu.se	spoel at gromacs.org   http://folding.bmc.uu.se