[gmx-users] Preferential interaction coefficient (PIC)

[ISHRAT JAHAN]

Dear all,
I have calculated the PIC of osmolytes using the following steps. Please
correct me if i m wrong at any point.
1. First i have calculated no. Of water and osmolytes molecule within 0.4
nm of protein using gmx select command  and named it as W-local and O-
local.
2. Then subtracted the no. Of W-local and O- local from to. No. Of water
and osmolytes molecule in order to get no. Of bulk water and bulk osmolytes
and named it as W-bulk and O-bulk.
3. Devide O-bulk by W-bulk and then multiply it by w-local.
4. Subtracted the value obtained in step 3 from O-local.
5. Averaged the whole value obtained from each frame at that distance.
6. Similarly i have calculated for other values of r.
Please correct me if i have done any mistakes . And also the value of PIC
obtained from this calculation is found to be very large approx 250. If the
calculation is right can i report this value.
Please reply ASAP.
Thanks