High symmetry for me means F432 .. no particular problem in H32
And of course the more molecules to find in the asymmetric unit the more
difficult it is..
But the general rule is
Rotation function harder the higher the symmetry - more likely to have
overlap between crystal symmetry and NCS
Translation function easier the higher the symmetry - more cross checking..
All programs more or less face the same difficulty.
But I always start with Molrep and Phaser - if they give a good solution
you are happy. If not I have to go back to Amore which is more
transparent IF you know its output..
Jay Thompson wrote:
> Hi All,
> I have a question- kinda general though. I've always heard of stories
> from people that molecular replacement is often difficult in high
> symmetry space groups, like R32, cubic, etc... I'm not quite sure I
> understand why that is the case? Is the molecular replacement
> difficult because in high symmetry space groups you have so many
> molecules in the unit cell and therefore the patterson vectors becomes
> more complicated and therefore more difficult to find a match during
> cross rotation/translation? If this is the case, I'm wondering if
> this is still a problem with today's computers and software? Do
> people have a favorite molecular replacement program they like to use
> specifically in high symmetry space groups? or are there programs
> that don't handle high symmetry space groups very well? Do people
> have a preference between Amore, Phaser, MolRep, epmr, and CNS? Any
> anecdotes would be appreciated. Thanks in advance!