impose two fold symmetry on helical density map

Submitted by gongpu zhao on Thu, 2011-02-17 15:13

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Frealign

I am wondering if I can impose a two fold symmetry on a helical reconstruction using frealign.

Thanks a lot.

niko Thu, 2011-02-17 19:44

If you know the repeat distance along the helical axis you should be able to impose two-fold symmetry by choosing

ALPHA  = 180 deg + helical twist angle associated by advancing one repeat
RISE   = repeat distance
STARTS = 2

gongpu zhao Tue, 2011-02-22 17:07

thanks for the advice. I actually try to add two fold dihedral symmetry that is perpendicular to the tube axis. In other words, can I impose H and D2 symmetry at the same time in frealign. Thanks.