This post announces the availability of a new release of the new CHARMM toppar files. These include the new C36 additive protein, nucleic acid, lipid, and carbohydrate releases as well as the CGenFF files as of July 2012. The toppar files are now in a new format that allows them to be read individually such that different parts of the force field (eg. proteins and nucleic acids) can be accessed without creating toppar files that contain both the protein and nucleic acid parameters. Note that this includes a toppar stream file for water and ions that must be explicitly read as water and the ions are no longer included in the biomolecular or CGenFF toppar files. See 00toppar_file_format.txt, included in the .tgz file, for details including an example on how to read the files into CHARMM.
have fun, alex
The gzipped tar file, toppar_c36_jul12.tgz
toppar_c36_aug12.tgz, containing the files may be accessed athttp://mackerell.umaryland.edu/CHARMM_ff_params.html
Reference for the new CHARMM36 protein FF.
Robert B. Best, R.B., Xiao Zhu, X., Shim, J., Lopes, P.,Mittal, J., Feig, M. and MacKerell, A.D., Jr. Optimization of the additive CHARMM all-atom protein force field targeting improved sampling of the backbone phi, psi and sidechain chi1 and chi2 dihedral angles. Journal of Chemical Theory and Computation, In press, DOI: 10.1021/ct300400x
Remaining references in the respective toppar files.