# [gmx-users] how to measure the surface tension of membrane by inclusion

Li Yang liyang1980_0_0 at 163.com
Thu Jul 17 16:13:26 CEST 2008

Hi

I have some questions about the surface tension calculations:

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 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.

Thank you very much.

Sincerely

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