Some things that are a good sign for having DNA as well as protein in your crystal:
1) You get different (or no) crystals if you add or substract a base or two from the DNA ends. Of course, we did get fooled by this logic once when one particular oligo seemed to be contaminated with an easily crystallizable mystery salt. 2) Unusually intense spots at ~3.4A, usually in the best direction of diffraction (due to the spacing between bp). If the DNA is a reasonable fraction of your scattering mass, it may be quite noticeable with hklview. 3) Anisotropic diffraction, often to far lower resolution than you'd hoped for. Also note that fragile hexagonal crystals might be DNA-only. Especially if the person setting up the trays tells you they were optimized by increasing the DNA:protein ratio ;-). Good luck! Phoebe ===================================== Phoebe A. Rice 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 http://www.rsc.org/shop/books/2008/9780854042722.asp ---- Original message ---- >Date: Sat, 1 Oct 2011 11:36:59 +0800 >From: CCP4 bulletin board <CCP4BB@JISCMAIL.AC.UK> (on behalf of zq deng ><dengzq1...@gmail.com>) >Subject: [ccp4bb] detect dsDNA >To: CCP4BB@JISCMAIL.AC.UK > > Hi all, > . > recently,I got a crystal of protein-DNA crystal.i > used silver stainto prove that it is a protein > crystal.Does anyone have method to detect if there > is DNA in the crystal. > any suggestion will be appreciated. > > Regards, > deng