You may have a fairly long cell edge (or two if you are dealing with P3 or P6), but you also seem to have high mosaicity (pic spot 1). Try the useful strategies suggested here. It may also be worthwhile to shoot a few roomtemp crystals to see if your cryo is at fault for your high mosaicity.
Bert On 4/5/11 9:10 AM, "dengzq1987" <dengzq1...@gmail.com> wrote: hello Jürgen_Bosch, because i have collected the data,but can't index.in some direction,the spot is separated .but the others are set close together(picture spot1 and spot 2).so we think there is one long unit cell axes. 2011-04-05 ________________________________ dengzq1987 ________________________________ 发件人： Jürgen_Bosch 发送时间： 2011-04-05 20:29:18 收件人： dengzq1987 抄送： CCP4BB@JISCMAIL.AC.UK 主题： Re: [ccp4bb] how to Collecting Data from Long Unit Cell Axes ? 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
