[gmx-users] Re: Re: problem about g_sas of POPC bilayer

David van der Spoel spoel at xray.bmc.uu.se
Fri Jun 6 08:47:53 CEST 2008


minnale wrote:
> 
> Thanks for your reply
> NO, I am having 64 lipids in each leaflet of bilayer. 
> I want to calculate average area per lipid.  what I have mentioned 
> options are correct for g_sas?

for area you use the box X times box Y divided by 64.
g_sas gives you solvent accessibe surfce area
> Thanks for your appreciation
> 
> innale wrote:
>  >  Hi all,
>  >    I have downloaded POPC bilayer from peter teileman,s website and
>  > simulated for 5ns under anisotropic pressure coupling. When I drew a 
>  > potential energy plot its shown that system is stabilised, so I have
>  > stopped the simulation at 5ns.
>  >  After that I have mentioned g_sas command for calculating surface area
>  > of lipid in this way and got .xvg file like below mentioned
>  >
>  > command : g_sas -f 5ns_popc.xtc -s min_popc.tpr -pbc -o area_popc.xvg
>  >
>  > .xvg File:
>  > @    title "Solvent Accessible Surface"
>  > @    xaxis  label "Time (ps)"
>  > @    yaxis  label "Area (nm\S2\N)"
>  > @TYPE xy
>  > @ view 0.15, 0.15, 0.75, 0.85
>  > @ legend on
>  > @ legend box on
>  > @ legend loctype view
>  > @ legend 0.78, 0.8
>  > @ legend length 2
>  > @ s0 legend "Hydrophobic"
>  > @ s1 legend "Hydrophilic"
>  > @ s2 legend "Total"
>  > @ s3 legend "D Gsolv"
>  >        0    152.383    228.165    380.548          0
>  >      0.2    149.279    230.277    379.555          0
>  >      0.4    153.175    229.306    382.481          0
>  >      0.6    149.312    229.188    378.499          0
>  >      0.8    149.708    228.811    378.518          0
>  >        1    149.972      229.69    379.662          0
>  >      1.2    155.587    229.615    385.202          0
>  >      1.4    151.953    227.696    379.649          0
>  >      1.6    149.113    229.903    379.016          0
>  >      1.8    151.062    227.394    378.456          0
>  >        2    149.278    226.934    376.213          0
>  >      2.2    151.095      225.68    376.774          0
>  >      2.4    149.873    229.576    379.449          0
>  >      2.6    148.387    230.391    378.778          0
>  >      2.8    147.627    227.792    375.419          0
>  >        3    148.156    229.589    377.745          0
>  >      3.2    145.051    229.568    374.619          0
>  >      3.4    147.231    229.814    377.044          0
>  >      3.6    145.348    229.392    374.741          0
>  >      3.8    148.717      229.43    378.146          0
>  >        4    153.307    230.834    384.142          0
>  >      4.2    153.604      230.6    384.204          0
>  >      4.4    154.397    229.345    383.742          0
>  >      4.6    155.718    230.864    386.582          0
>  >      4.8    155.685    231.226    386.911          0
>  >        5    152.911    231.332    384.243          0
>  >      5.2    153.935    229.453    383.388          0
>  >      5.4      154.43    231.396    385.826          0
>  >        .                               
>  >        .
>  >        .
>  >        .
>  >        .
>  >      till 5000ps.
>  >
>  > I have searched in gmx-archives about SAS of lipid, I found that lipid 
>  > SAS should be 0.64 nm^2/sec but I got values range from 150 to 170nm2/sec
> 
>  >>Let me guess, .64 x 256 = 150 nm^2. Do you have 256 lipids?
> 
>  >
>  > Could you please tell where I have done mistake?
>  > Thanks in advance.
> 
> 
> 
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-- 
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



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