Disu patch for charmm22 force field will results in error messages: cannot find 1HG and 2HG. Solution: modify charmm22/topallh22x.pro and change 1HG into 1HG1, 2HG into 2HG1 in Preresidue DISU. After that you could find the Preresidue-DISU is consistant with topology files in charmm pakage :)