These kind of "crystals" are very common with DDM, I guess they could be called spherulites. Sometimes they develop one or a few straight edges after a while. I don't think these are DDM crystals as DDM is very soluble, but protein-detergent crystals that are dominated by weak detergent micelle interactions and are not or very poorly ordered.
You're right, crystallisation in DDM is tough but often it is the only choice. Good luck, bert ________________________________ From: CCP4 bulletin board <CCP4BB@JISCMAIL.AC.UK> on behalf of Thomas Warwick <pax...@nottingham.ac.uk> Sent: 16 June 2017 15:23 To: CCP4BB@JISCMAIL.AC.UK Subject: [ccp4bb] Can DDM give egregious false positives when using it to crystallize membrane proteins? Hi, all. I have obtained some crystals (see the imgur link) from my crystal trials of a membrane protein and I'm concerned that they may be detergent, DDM. The drop condition is: 0.2M NaCl 0.1M HEPES @ pH 7.0 22% PEG500 MME Protein sample contains (GF running buffer): 0.02M Tris 0.1M NaCl 0.03% w/v DDM with 1mM TCEP-HCl added just prior to the trial. Please note however I concentrated GF eluent fractions 18-fold prior to the trial with a spin concentrator whose cutoff was smaller than the relative mass of an empty DDM micelle (it's a small protein) and therefore the DDM concentration could theoretically be 0.03% x 18 = 0.54% = 10mM... The crystals are fragile and oily and occur in a plethora of drops with varying visual regularity. I've screened a crystal at a synchrotron and it exhibited essentially amorphous diffraction. Has anybody experienced similar entities forming when laying down crystal trials of membrane proteins solubilized in DDM? If so do they contain protein? It's my undestanding that DDM is extremely hard to crystallize. Any information would be appreciated http://imgur.com/a/AsZHs (the crystals) [http://i.imgur.com/F1doLyr.jpg?fb]<http://imgur.com/a/AsZHs> Imgur: The most awesome images on the Internet<http://imgur.com/a/AsZHs> imgur.com Imgur: The most awesome images on the Internet. http://imgur.com/a/m88rn (their diffraction pattern) [http://i.imgur.com/Xb5gAzS.jpg?fb]<http://imgur.com/a/m88rn> Imgur: The most awesome images on the Internet<http://imgur.com/a/m88rn> imgur.com Imgur: The most awesome images on the Internet. Cheers, Tom PhD Student within the Structural Biology Group at the University of Nottingham. Email: pax...@nottingham.ac.uk
