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..
Eleanor
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!
Jay
