Dear Allen, Sue,
we also have had some luck with ACORN, but as our peptide did not have
alpha-helical structure, the postdoc on the project used a 4-aa
beta-turn fragment instead. I can put you in contact with him for more
details. As I understand it, ACORN uses a mixed MR/direct methods
If you have 1.1A data and your structure is not too large, ab initio
direct methods (e.g. with SHELXD) will probably solve the structure. I
would be happy to advise if you wish to try this.
George
Prof. George M. Sheldrick FRS
Dept. Structural Chemistry,
University of Goettingen,
Tammannstr.
Hi Allen,
With such low solvent content (and corresponding tight packing), you may
want to give 'Queen of spades (Qs)' a try. The reason being that Qs is not
(at least directly) a Patterson-based method (and does not assume that
intra-molecular vectors are topologically segregated). If you
I am trying to do molecular replacement on a small peptide (less than 40 AA)
and have not had any success using phaser. Are there any tricks or better
programs for really small peptides?
The data is great 1.1 A, ~35% solvent, and two molecules in the ASU. I have
tried all the standard stuff,
Have you tried acorn in ccp4? I've had it work well at this resolution,
especially if the protein/peptide has some alpha helical content. We used
acorn to solve a small cro protein that we couldn't get molecular replacement
to work with by using a 5-residue ideal poly-ala helix as the starting
I've had good luck using Phaser on test cases like that, but haven't
had access to a case that was previously unsolved. But in principle
it should work, if the model is good enough.
It sounds like you've thought about the resolution already, so this is
probably redundant. Anyway, the
