Dear dengzq1987, while we are bragging about long cells and high resolution, our bacteriophage T4 short tail fibre crystals of spacegroup P321 had cell axes of a=b=50.7 Å, c=436 Å, but we got a very good 1.5 Å resolution dataset for it (pdb code 1OCY). The crystals were long rods with hexagonal cross-section. From your explanations it seems you may have a similar case. It was absolutely essential to mount them with the long axis more or less along the rotation axis, luckily they tended to orient this way naturally. Our crystals did not have a specially low mosaic spread (0.3-0.5 degrees), but we did use a low-divergence beam collimated asymmetrically to separate the spot as well as possible on the images (if you have only one long axis and the crystal is oriented with it along the rotation axis, you only have to worry about the easily visible spot overlap on the actual images). If they do not naturally orient the "right" way, bent loops and/or kappa goniometer are very useful (I used them for another project).
From your images, it is clear your rotation axis was not along the long axis of the unit cell. Your best bet is to grow more crystals if necessary, try to orient them in different ways in the loop and measure images for indexing at low-res to get a feeling for this type of crystals. Then, when you are confident, try to get an as high as possible resolution dataset at the synchrotron. Of course, I do not know if you will need phases also. Greetings, Mark Mark J van Raaij Laboratorio M-4 Dpto de Estructura de Macromoleculas Centro Nacional de Biotecnologia - CSIC c/Darwin 3, Campus Cantoblanco E-28049 Madrid, Spain tel. (+34) 91 585 4616 http://www.cnb.csic.es/content/research/macromolecular/mvraaij/index.php?l=1 On 5 Apr 2011, at 15:12, dengzq1987 wrote: > my crystal is not plate.it is Hexagonal and very large. > > > 2011-04-05 > dengzq1987 > 发件人： Jacob Keller > 发送时间： 2011-04-05 20:53:41 > 收件人： CCP4BB > 抄送： > 主题： Re: [ccp4bb] how to Collecting Data from Long Unit Cell Axes ? > For plate crystals with the long axis normal to the plate surface > (anecdotally, this is usually the case), you can use bent loops. Bent > loops can be made using tweezers by folding over the loop onto the > stem and crimping with the tweezers. When the loop relaxes a bit, it > will leave a ~90deg-bent loop, so the crystal can sit on the loop and > be shot edge-on in the beam. It takes a bit of time to get it right, > but it worked well for me one time. > JPK > On Tue, Apr 5, 2011 at 7:29 AM, Jürgen Bosch <jubo...@jhsph.edu> wrote: > > What do you consider long ? 200, 300 ? 600 A ? Before shooting try to run > > strategy or xplan. Move the detector back to first reliably be able to > > determine your cell. Then double your estimated mosaicity and see what > > strategy suggests. If you don't get many overlaps (<5%) then try a closer > > distance. Don't rotate 1degrees but take 1/2 of the mosaicity. Obviously you > > want to make good use of the detector area so adjust the edges to where your > > crystal really diffracts. And if that resolution leads to too many overlaps > > then limit your resolution and get first a good datasets home. You then can > > play with 2theta for a higher resolution dataset. > > Another obvious thing to do and you don't mention what reduction program you > > use is to let XDS sort your problem out. Unless you collected to high > > resolution without being cautious XDS could help. If not, well then you had > > your experience and now should know better. > > SSRL has options to collect 450 A cells to 3A without much hassle. That was > > my largest cell so far. > > Jürgen > > > > ...................... > > Jürgen Bosch > > Johns Hopkins Bloomberg School of Public Health > > Department of Biochemistry & Molecular Biology > > Johns Hopkins Malaria Research Institute > > 615 North Wolfe Street, W8708 > > Baltimore, MD 21205 > > Phone: +1-410-614-4742 > > Lab: +1-410-614-4894 > > Fax: +1-410-955-3655 > > http://web.mac.com/bosch_lab/ > > On Apr 5, 2011, at 1:05, dengzq1987 <dengzq1...@gmail.com> wrote: > > > > hello all, > > does anyone have the experience of Collecting Data from Long Unit Cell Axes > > ? I have a crystal that diffracts to about 4 A. in some direction the spots > > overlap. we can't use the data to index .we think it is because that there > > is a long unit cell axes. so is there any method to solve this problem? > > > > best wishes. > > > > 2011-04-05 > > ________________________________ > > dengzq1987 > -- > ******************************************* > Jacob Pearson Keller > Northwestern University > Medical Scientist Training Program > cel: 773.608.9185 > email: j-kell...@northwestern.edu > *******************************************
