<html><div style='background-color:'><P>Dear alll,</P>
<P>I'm trying to carry out a MD simulation on a small RNA molecule. Then I've downloaded the ffamber99 force field port for gromacs ,modified my pdb file and runed pdb2gmx. I've solvated the system using ffamber_tip4p files and neutralized the system charge using Na+ ions.</P>
<P>But when I run grompp command for energy minimization the software is not able to recognize Na+ ions (I tryed to write it in all possible ways, NA+, NA, Na+ and Na, but the results are the same).</P>
<P>How may I do?</P>
<P>Thanks in advance.</P>
<P>Bests,<BR><FONT face="Lucida Handwriting, Cursive">Sara Pistolesi</FONT></P></div></html>