:) Gerard, "soaking"! Thanks for the reference! cheers guenter
Dear Guenter,The first description of the idea behind this technique that I am aware of is that published almost 10 years ago by a French group under the name of "'dry' co-crystallisation" in the following paper: http://dx.doi.org/10.1107/S1399004715010342 Best wishes, Gerard -- On Fri, Oct 04, 2024 at 05:40:12PM +0200, Guenter Fritz wrote:Hi Amit, like Artem wrote below, even despite poor solubility, soaks with dried compounds work well (also in our hands). We adapted it from the work of T. Barthel, J. Wollenhaupt and Manfred Weiss. Also colleagues from industry report good results. We add compound dissolved in DMSO to the crystallization well, let DMSO evaporate overnight (37° incubator), then put mother liquor on top of the dried compound and then the crystals. If all compound would dissolve again, final concentration would be 10-50 mM. Soak time from 1-2 h to overnight. This worked for poorly soluble compounds where we did not succeed with soaking in the presence of DMSO. Hope that helps! Best, GuenterDear Amit As David already pointed out, all proteins are different and it's hard to say in advance what amount of DMSO may work (or not). An additional concern is that DMSO can also interfere with ligand binding (cases from my personal past history), especially if these inhibitors/ligands are on the weaker side. Solutions: Despite its very high boiling point (189C) DMSO can in fact be evaporated from a small sample of your inhibitor, resulting in more or less solid inhibitor sample that can be re-dissolved in the same DMSO (but higher concentration), some other solvent, or perhaps directly in the protein solution. The latter is sometimes the only way to do this - I used to set up drops of DMSO solutions, then evaporate the DMSO in high vacuum (heating helps) with a cryofinger, then set up protein drops on top. This of course requires access to a lyophilizer or something similar. If you have a vial of your solution you can freeze-dry DMSO with water, by first diluting the sample then freeze-drying it. Also water can sometimes crash the substance out (if not water, then perhaps Ether or another solvent where your inhibitor does not dissolve) which makes it easier to redissolve (but there will be a loss of course). Find a friendly chemist nearby and ask then to put your sample in a speedvac on 'high BP' setting Notably, if you're "blessed" with an inhibitor that has the general solubility of a Sony Walkman, once you get rid of the DMSO, you may find out that the damned thing does not want to dissolve in anything else, including your protein solution. This happens a lot during early discovery phases when compounds are not very active (micromolar) and also poorly soluble (also micromolar). This is by far the most frequent cause for failing to co-crystallize (or soak) a ligand of interest. Very frustrating. Some success can be achieved using high DMSO or DMF (DMA also can be good) in your crystallization, or by phase transfer catalysts like Cyclodextrin(s) or appropriately formulated micelles. All of which can also mess up crystallization, needless to say. Best of luck in your endeavors! Artem - Cosmic Cats approve of this message On Wed, Oct 2, 2024 at 2:51 PM amit gaur <cdriamitg...@gmail.com> wrote: Hi everyone, I am trying to crystallize a protein with a drug molecule. The protein concentration is 15.5 mg/ml, the drug stock concentration is 10 mM, and the drug is dissolved in DMSO. I am adding the drug to a final concentration of 1 mM in 100 ul of protein, and the DMSO volume is 10 ul for Co-crystallization. I want to know how much DMSO is permissible during co-crystallization with the drug and if DMSO can poison crystal formation. I have not been successful in getting crystals with inhibitors till now, but I obtained crystals of protein without DMSO, and those diffracted to 2.5A. Thanks, *Dr. Amit Gaur,* *Research Scientist* *Center for Biotechnology and **Interdisciplinary Studies,* *Rensselaer Polytechnic Institute,* *1623 15th Street, Troy, NY, 12180* * * ------------------------------------------------------------------------ To unsubscribe from the CCP4BB list, click the following link: https://www.jiscmail.ac.uk/cgi-bin/WA-JISC.exe?SUBED1=CCP4BB&A=1 <https://www.jiscmail.ac.uk/cgi-bin/WA-JISC.exe?SUBED1=CCP4BB&A=1> ------------------------------------------------------------------------ To unsubscribe from the CCP4BB list, click the following link: https://www.jiscmail.ac.uk/cgi-bin/WA-JISC.exe?SUBED1=CCP4BB&A=1 <https://www.jiscmail.ac.uk/cgi-bin/WA-JISC.exe?SUBED1=CCP4BB&A=1>######################################################################## To unsubscribe from the CCP4BB list, click the following link: https://www.jiscmail.ac.uk/cgi-bin/WA-JISC.exe?SUBED1=CCP4BB&A=1 This message was issued to members of www.jiscmail.ac.uk/CCP4BB, a mailing list hosted by www.jiscmail.ac.uk, terms & conditions are available at https://www.jiscmail.ac.uk/policyandsecurity/
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