I've seen this kind of thing before.
Case 1: two crystal forms in the same droplet, C2 and C222. If you
looked closely, you could tell them apart and I was pretty good at
getting a high percentage of the desired space group by looking at the
crystal forms. The C2 form diffracted better, so I fished for that one.
Case 2: A mixture of crystals, C2 and C2 with the long axis doubled in
length, caused by asymmetric ligand binding. In the "double-size" C2
crystal form, ligands bound to only 10 of the 12 chains in the
double-size ASU, which no longer conformed to two adjacent "normal-size"
C2 ASUs. In the "normal" size C2 form, all 6 protein chains in the ASU
bound ligand.
Cheers,
_______________________________________
Roger S. Rowlett
Gordon & Dorothy Kline Professor
Department of Chemistry
Colgate University
13 Oak Drive
Hamilton, NY 13346
tel: (315)-228-7245
ofc: (315)-228-7395
fax: (315)-228-7935
email: rrowl...@colgate.edu
On 10/28/2016 9:13 AM, Sam Tang wrote:
Dear all
Sorry for going a bit off-topic in this thread.
May I seek your advice as on whether you have experienced that
crystals being obtained from the same droplet, looking alike under
microscope (rod shape) and in fact growing possibly from a same
nuclei, give two space groups after indexing?
I recently obtain crystals for a protein (co-crystallized with a
nucleic acid ligand) and collected two datasets from synchrotron.
Although these two crystals are from the same drop, the SG and unit
cell dimensions are very different:
Xtal1: C121 (156 60 105 90 111 90) (L-test, Pointless shows that there
is no twinning), ~2.5 Angstrom
Xtal2: P1 (53 60 79 106 105 98), ~3 Angstorm
Would it be possible that the ligand changes the SG of the crystal so
that only one of the forms contains the ligand?
Any advice is appreciated and thanks a lot in advance for your input.
Regards
Sam Tang
Biochemistry Programme, School of Life Sciences, CUHK
