[gmx-users] butane-parameters

[rversace at ccny.cuny.edu]

Hi Everybody:

I am trying to perform a MD simulation of n-butane. But I cannot find the gromacs paramaters for it. In the 2005 paper from Lange about Flooding in GROMACS (J.Comp.Chem 21:1693.2006), the authors performed this simulation before using the ffgmx united atom force field. But I cannot find the butane topology and parameters inside that forcefield. 
When I use pdb2gmx on my butane.pdb I get the following message:

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Program pdb2gmx, VERSION 4.0.4
Source code file: resall.c, line: 426

Fatal error:
Residue 'BUT' not found in residue topology database

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Does anybody know where can it be or maybe it has another residue name in the rtp file?  

Thanks