[gmx-users] K+ gain

Semen Esilevsky yesint4 at yahoo.com
Tue Jul 8 09:08:00 CEST 2003

Hi all,
I'm just started using GROMACS and thus have a lot of
questions. The current one is the following:
I've tried to simulate the much abused KcsA potassium
channel containing 3 K+ ions in the structure. I've
got the message "unknown residue type: K" when runing
pdb2gmx. But there IS K+ in the force-field files! 
I've found several postings reporting this problem and
even ions.itp file correcting it. The problem is that
I can't understand where to place it.
The only way I've found is to assign all K+ parameters
to Rb+ and manually change K+ to Rb+ in .pdb (stupid,
but working)
Could someone explain in details how to deal with this

Remark: All ions seems to work fine except K+. Is it a
bug or a feature ;)


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