I am trying to study the dynamics of a prticular protein with its post translational modifications. An unparameterized acetyl group covelantly bound to a lysine residue denies the generation of PSF and PDB files for solvation and ionization. I have gone through the manual for NAMD "parametrizing a novel residue " and also used CHARMM GUI, for parameter and topology generation. it maybe the case that unknowingly I might have missed or displaced any files during the procedure. I would be a great help if I get a step by step solution to it. Thanks.