Hi
The absence of clearly separate lunes on the first image indicates that the
mosaic spread is rather high. If you increase the intensity threshold in spot
finding you may be able to pick out spots belonging to a single lattice. If you
increase the intensity threshold in autoindexing you may also be able to do
this. My understanding is that HKL will let you do either or both, but of
course I'd prefer you to do it in Mosflm ;-)
Looking at the higher resolution spots in the top left of the first image, it
looks like you have three major crystals (at least) contributing to the
diffraction - some of the spots are split into three close components - you may
need to tune the spot finding parameters to either include all three components
as one spot in each case, or perhaps just pick the strongest component. Because
the spots are spread radially from the beam centre, I'd guess that the unit
cell edges of the three components in that direction are a bit different.
The second image indicates that you have a long axis almost aligned with the
vertical (~80º to the backstop shadow). The streaking together often happens if
you've only got a few unit cells along that axis- actually not that unusual.
Again, if you tune your spot-finding parameters carefully (small spot size,
small separation between spots) you may be able to pick out individual spots
and index successfully.
I'd ask your assistant professor what he/she did to index successfully - he/she
seems to know what he/she's doing!
On 29 Nov 2010, at 17:14, chen c wrote:
I attached two diffraction images of my crystal, of which one seems normal as
protein crystal usually do, while the other one looks very strange ,with very
continuous lines on the image.
In fact, of the 180 crystal images diffracted by my crystal, there is a
tendency between those two.
I had thought that my crystal is a combination of many two-dimensional
crystals, between wich there are translational or rotational translocations,
namely resulting in a lack of translational symmetry in the third axes. As a
result of this, when I tried to index them using HKL2000, one of the cell
parameter is merely several angstroms.
However, of the several data sets from different crystals, one data set is
sucessfully indexed by the assistant professor of my laboratory and currently
submitted to the operation of Molucular Replacement.
This confused me a lot. Is what I thought wrong? Or is the very crystal that
was indexed a special one?
Thanks all
chen
normal.jpgmore typical-1.jpg
Harry
--
Dr Harry Powell, MRC Laboratory of Molecular Biology, MRC Centre, Hills Road,
Cambridge, CB2 0QH
