Dear Derrick,
please check paper manual
ftp://ftp.gromacs.org/pub/manual/3.2/manual-3.2.pdf
chapter 5.5.1
DGYL> [ atoms ]
DGYL> N opls_238 -0.500 1
atom atom charge charge
name type group
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Best regards,
Andrey mailto:golovin at genebee.msu.su