Dear Min, regarding #1 some things come to my mind:
- What is the Kd that you got from the Biacore? And did you make sure that the sample is concentrated enough (both on gel filtration and in crystallization) to have a "sufficient" amount in the complex. - did you use the same buffer systems? Your Kd might be different in different buffers. Best Alex Dr. Alexander Pautsch Boehringer Ingelheim Pharma GmbH & Co. KG Dept. Lead Identific. and Optim. Sup. Ge Tel.: +49 (7351) 54-4683 Fax: +49 (7351) 54-97924 mailto:alexander.paut...@boehringer-ingelheim.com <mailto:alexander.paut...@boehringer-ingelheim.com> Boehringer Ingelheim Pharma GmbH & Co. KG, Sitz: Ingelheim am Rhein; Registergericht Mainz: HR A 22206; Komplementär Boehringer Ingelheim Deutschland GmbH; Geschäftsführung: Dr. Engelbert Günster (Vorsitzender), Ralf Gorniak, Mark Hagmann, Michael Klein, Dr. Martin Wanning; Vorsitzender des Aufsichtsrates: Prof. Dr. Dr. Andreas Barner; Sitz: Ingelheim am Rhein; Registergericht Mainz: HR B 23260 Diese E-Mail ist vertraulich zu behandeln. Sie kann besonderem rechtlichen Schutz unterliegen. Wenn Sie nicht der richtige Adressat sind, senden Sie bitte diese E-Mail an den Absender zurück, löschen die eingegangene E-Mail und geben den Inhalt der E-Mail nicht weiter. Jegliche unbefugte Bearbeitung, Nutzung, Vervielfältigung oder Verbreitung ist verboten. / This e-mail is confidential and may also be legally privileged. If you are not the intended recipient please reply to sender, delete the e-mail and do not disclose its contents to any person. Any unauthorized review, use, disclosure, copying or distribution is strictly prohibited. Von: CCP4 bulletin board [mailto:CCP4BB@JISCMAIL.AC.UK] Im Auftrag von m zhang Gesendet: Freitag, 16. September 2011 04:20 An: CCP4BB@JISCMAIL.AC.UK Betreff: [ccp4bb] crystallization of complex and ... Dear all, I have two questions: First, I was trying to crystallize a complex of two proteins. Both proteins has been crystallized before. The two proteins bind to each other based on Biacore study, but they didn't form a single peak on gel filtration. When I mixed them at 1:1 ratio, the crystals I got contain only one of the two proteins. I was suggested to increase the ratio, for example 1.5:1, to increase the probability of co-crystallization which I will try. But I do want to hear if there are other possible ways to try. What would you try if you were in my situation? Second is about reusing of Ni-NTA resin. According to Qiagen's instruction, after using fresh Ni-NTA resin, one only needs to wash the used Ni resin first with 0.5M NaOH, then with your own buffer. After that the resin is ready to be reused until it needs being recharged. But my question is: Once immidazole competes with His-tagged protein and binds to Ni-resin, how can immidazole be rinsed off with the same buffer(usually pH is above 7) one uses to purify the protein? Thank you for any suggestion or comment. Min
