<table cellspacing="0" cellpadding="0" border="0" ><tr><td valign="top" style="font: inherit;"><DIV>Dear gmx-users:</DIV>
<DIV>When I try to simulation a system: protein + ligand molecule using the Implicit Solvent method. the parameters of Ligand were produced by acpype, but when grompped, the appeared" </DIV>
<DIV>" Velocities were taken from a Maxwell distribution at 300 K</DIV>
<DIV>GB parameter(s) missing or negative for atom type 'o'</DIV>
<DIV>GB parameter(s) missing or negative for atom type 'os'</DIV>
<DIV>GB parameter(s) missing or negative for atom type 'c'</DIV>
<DIV>GB parameter(s) missing or negative for atom type 'c3'</DIV>
<DIV>GB parameter(s) missing or negative for atom type 'hc'</DIV>
<DIV>GB parameter(s) missing or negative for atom type 'h1'</DIV>
<DIV>-------------------------------------------------------<BR>Program grompp_d, VERSION 4.5.3<BR>Source code file: grompp.c, line: 1123</DIV>
<DIV>Fatal error:<BR>Can't do GB electrostatics; the implicit_genborn_params section of the forcefield is missing parameters for 6 atomtypes or they might be negative."</DIV>
<DIV>when I modified "<A class=plink href="http://cn.webmessenger.yahoo.com/index.php?t=1&to=eWlkPXpoYW94aWl0YzIwMDI-&sig=703fa929658518b2720b087c59cd85f2dabf8844" rel=nofollow target=_blank><IMG class=pimg border=0 alt=4 src="http://opi.yahoo.com/online?u=zhaoxiitc2002&t=4&l=cn"></A>amber99sbr.ff/gbsa.itp by adding the atomtype of ligand, the problem is still the same, </DIV>
<DIV>please give me some suggestions</DIV>
<DIV>Thank you! </DIV></td></tr></table>