Depends a bit on what the "streaks" look like. If they are curved, and
your "streaks" are connecting partial rings at different resolutions,
then what you may be seeing is simply diffuse scatter from a "small
molecule", such as ice. The only way to be sure you are looking at
protein is if you see spots at low angle, and the d-spacing of the
innermost spots is at least big enough to fit your protein inside it in
P1 with a bit of solvent left over.
If you do have ice, then it is still possible you had a protein crystal,
and just need to work on cryo-protection conditions.
HTH
-James Holton
MAD Scientist
On 10/3/2013 5:40 AM, Krithika GOkulnath wrote:
I introduce myself as Dr.Krithika Gokulnath, CAS in crystallography and
Biophysics, UNiversity of Madras. I have been working with a cloned protein and
have been successfully able to crystallise it. However data collection done at
home source shows a pattern of streaks instead of spots. The crystallization
set up contained 12% PEG 8000, 10mM Magnesium chloride, 200mM Potassium
chloride in 50 mM Tris pH 7.0. The protein is an enzyme which is also in the
buffer containing the above components excepting the precipitant. It is a
tetramer at native conditions and molecular weight on SDS-PAGE is 54 Kda.
Kindly share your suggestions and speculations on what might be the reason for
the streaking. The streaks are many wide spread and there are no high
resolution spots or streaks as we might expect in salt crystals.
