[gmx-users] g_covar + g_anaeig entropy calculation

[Albert]

Hello:

I am trying to calculate ligand binding energy for  protein/ligand 
system. The enthapy part was done by GMXPBSA. Now I would like to 
evalutate the entropy part with g_covar + g_anaeig.

Here I got some questions:

--- is it necessary using double precison Gromacs for entropy evaluation?

--- I googled a lot concering on this topic from Gromacs mailist. If I 
understand correctly, we should
(1) generate eigenvec.trr as input file for g_anaeig
(2) use g_anaeig calculate the entropy

is it correct?

---I am trying to run command:
g_covar -f input.xtc -s input.tpr -n -o eigenval.xvg -v eigenvec.trr -av 
average.pdb -l covar.log -ascii covar.dat -xpm covar.xpm -xpma covara.xpm

The trajecotry I am using for above commend was extracted from MD 
simulations and water/ions were removed from the system. When g_covar 
pop up a dialoug asking which compoenent I am going to analyze, I 
selected "System" which contains protien+ligand

Is it correct to do so?

---I am planning to run g_anaeig with following command for entropy 
evaluation:
g_anaeig -v  eigenvec.trr -entropy  -s input.tpr  -comp

Shall I speicify additional options for this purpose?

Thank you very much.

Albert