Which forcefield you want? CHARMM, Amber, GROMOS, OPLS etc.. Please modify your query and give detailed description?

For CHARMM: http://mackerell.umaryland.edu/charmm_ff.shtml

Dear Nandan Kumar

I am looking for a force field for ATP molecule. I tried with all the force fields that are natively available. I am using gromacs 5.1.1

Pritam Kumar Panda Nandan Kumar

Thank you so much for sharing !

Krithika Unmesh This can be sorted out in two ways. I will start with the easiest one but it is bit crude. You can actually look for the atp paramters in other forcefiled files in the gromacs folder. It must be there in some forcefield.itp or atomtypes.rtp (i am not sure with the file names but i guess the file format is .rtp)files in any of the many forcefield folders. just copy it to your desired forcefield folder and rewrite the parameters according to you focefield of interest. This is the easiest way to solve the problem. But then you should REMEMBER that different forcefields pair potentials will be different. So sometimes it might create an artifact in ur system. That depends upon your system and the method of study you are anticipating.

Second one is rather neat and more reliable. You can model the ATP and do some optimizations for it. Then write the parameters in the desired forcefield format and add it to you r topology. This looks simpler but the optimization and writing the forcefield would take quite sometime.

To begin I would go with the first solution because it is rather easy and I could able to derive some insights about the systems from the simulaitons. But then to have a conformation I would do the second one.

Cheers

Govind

Gokul Govind Thank you !