Force-fields are an essential part of molecular mechanics simulations. The force-field parameters, along with the chosen molecular mechanics energy function, are one of the most important factors in the successful application of molecular mechanics. If the force-field parameters are of a poor standard, then the molecular mechanics results will follow suit.
Most standard force-fields were parameterized against a set of test compounds. If your system is far removed from the chemical species found in the test set of your chosen force-field, then the parameters may not provide the best results. This could mean missing out on a potentially active ligand or result in wasted resources pursuing a false positive, either way it is an undesirable situation.
Sometimes parameters, for a given species, are not even available within a particular force-field. In this case some software programs, e.g. Discovery Studio, can provide an estimate based on the average values of similar species. These parameters are likely to only provide rough estimates of real chemistry at best. Discovery Studio users are recommended not to take these parameters as correct but to carry out further optimization. The same principal applies for other computational chemistry packages providing molecular mechanics functionality.
We can provide you with fully optimized force-field parameters for your species of interest, for your chosen force-field, in keeping with the standards of your chosen methodology and original force-field specification. This will help to give better results that you can rely on, whilst maximising your time on using your computaional chemistry software to drive progress rather than concentrating on time-consuming parameterization.