Move the beam stop back? My lab has grown quite a few crystals that only diffract to very low resolution. Phoebe (with sympathy!)
---- Original message ---- >Date: Mon, 19 Apr 2010 11:35:11 +0800 >From: tat cheung cheng <theif...@yahoo.com.hk> >Subject: [ccp4bb] Re： [ccp4bb] Mysterious Crystals? >To: CCP4BB@JISCMAIL.AC.UK > > Thank you. Forget to mention, no diffraction > observed no matter with or without cyro cooling. > > ------------------------------------------------ > > 寄件人﹕ "tom.p...@csiro.au" <tom.p...@csiro.au> > 收件人﹕ theif...@yahoo.com.hk > 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:ccp...@jiscmail.ac.uk] On Behalf Of tat > cheung cheng > Sent: Monday, 19 April 2010 1:26 PM > To: CCP4BB@JISCMAIL.AC.UK > 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 <jubo...@jhsph.edu> > 收件人﹕ CCP4BB@JISCMAIL.AC.UK > 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 > > 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/ > > > > > > Phoebe A. Rice Assoc. Prof., Dept. of Biochemistry & Molecular Biology The University of Chicago phone 773 834 1723 http://bmb.bsd.uchicago.edu/Faculty_and_Research/01_Faculty/01_Faculty_Alphabetically.php?faculty_id=123 RNA is really nifty DNA is over fifty We have put them both in one book Please do take a really good look http://www.rsc.org/shop/books/2008/9780854042722.asp
