Thank you. Forget to mention, no diffraction observed no matter with or without cyro cooling.
________________________________ 寄件人﹕ "[email protected]" <[email protected]> 收件人﹕ [email protected] 傳送日期﹕ 2010/4/19 (一) 11:29:38 AM 主題： RE: [ccp4bb] Re： [ccp4bb] Mysterious Crystals? Hello Tc, It isn’t that unusual to get protein crystals that don’t diffract. This happens probably 50% of the time. One can try dehydration of the crystals, crystal annealing and additive screens to see if any of these things will give you some diffraction. In addition, you didn’t mention whether you froze these crystals- one should also try putting a crystal in the beam without cryo-cooling, as cryo-cooling can often be detrimental to diffraction. Cheers, tom ________________________________ From:CCP4 bulletin board [mailto:[email protected]] On Behalf Of tat cheung cheng Sent: Monday, 19 April 2010 1:26 PM To: [email protected] Subject: [ccp4bb] Re：[ccp4bb] Mysterious Crystals? Yes, I have just done that. They are protein. But if they are protein, why no diffraction? That's intriguing. ________________________________ 寄件人﹕Jürgen Bosch <[email protected]> 收件人﹕[email protected] 傳送日期﹕2010/4/19 (一) 10:57:40 AM 主題：Re: [ccp4bb] Mysterious Crystals? Fish and wash some crystals then run them on a SDS-gel, then you will know for sure if it's protein or not. J僡gen On Apr 18, 2010, at 10:46 PM, tat cheung cheng wrote: Hi all, I have got some crystals, the purified protein was in Tris buffer with 300mM NaCl for crystallization. they grew in light weight PEG, PEG400 or monomethyl ethyl PEG500, they were needle shaped, could be long (~0.2mm) but very thin all the time and sometimes grew into sea-urchin like needle cluster. What interesting is, when i gridded crystallization conditions against pH or PEG amount, the crystals sizes and shapes varied, and the crystals were fragile so i believed they were protein crystals in nature. But upon X-ray diffraction, they gave no reflection at all, not even a faint spot. I wonder, beside silly mistakes like misalignment of the crystal to the beam, not enough exposure time, what could be the reason for this mysterious crystals? Are they protein or PEG or what? Thanks very much. Tc - J僡gen Bosch JohnsHopkins Bloomberg Schoolof 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/
