[Chimera-users] make helical filament model using command sym

Dear all, I have built a model from cryo-em density map, now I am going to create a model of a filament (have a length of the pitch, over 1000 A) from it. I think the command 'sym' can do it, but not easy for me. I have tried many times. sym #0 group h,rise,twist,100 or sym #0 group c2*h,rise,twist,100 coord #1 or sym #0 group h,2.292,179.6,100 coord #1 the model is wrong I also try to measure the symmetry first and sym #0 group #1 it is almost right, but I need much longer, how set it? using the 'n' parameter? and how? and if I want to set rise and twist myself, how to do it? Best wishes, Yaowang