Hi Ngo,
your needles actually look like very thin plates. They seem promising to me.
From appearance its impossible to tell whether the crystals are detergent or
not. DDM is apparently known to form crystals, but I've never really gotten any
(DDM is very soluble). What temperature have you used? 4C would favor forming
DDM crystals. The round crystals are often seen in membrane protein
crystallization. They generally don't diffract, contain a lot of detergent
(maybe all detergent) and are very hard to get better (ie get sharp edges
and/or diffraction).
What I would do at this point is trying to get the needle/plate crystals better
(by using techniques/tricks that are used for soluble proteins, such as vary
Mg2+ salt conc and identity, temperature, volume/reservoir ratio, protein conc.
and even trying different detergents and/or mixtures including DDM). For now I
would go with the assumption that the crystals are protein.
Good luck!
Bert van den Berg
University of Massachusetts Medical School
Program in Molecular Medicine
Biotech II, 373 Plantation Street, Suite 115
Worcester MA 01605
Phone: 508 856 1201 (office); 508 856 1211 (lab)
e-mail: [EMAIL PROTECTED]
http://www.umassmed.edu/pmm/faculty/vandenberg.cfm
________________________________
From: CCP4 bulletin board on behalf of Ngo Duc Tri
Sent: Wed 4/16/2008 9:48 AM
To: CCP4BB@JISCMAIL.AC.UK
Subject: Re: [ccp4bb] Optimization of needle crystals?
Dear experts,
You didn't mention which detergent in the conditions. From the picture
it looks
like crystals of detergent.
The initial buffer contains 50mM Tris 7.7, 100mM NaCl and 0.015% DDM.
I got two forms of crystal: needle and round shape.
The needle crystals grow from conditions containing Mg2+ salt and high pH.
The round crystal grow from conditions containing Mg2+, high pH and small PEG.
I already fail to optimize the round shape (by changing the PEG concentration
as well as pH or protein concentration). So that's the reason why I think about
optimization of the needle form.
Here I attach more pictures to show you the needle and the round crystal. I
never applied powder diffraction before so maybe it's hard for me to confirm
it's the crystal of detergent or not.
Thank you very much for all of your helpful suggestion!
My best regards,
TriNgo
PhD Student- Sungkyunkwan University, Korea
