Simon, solubilize your ligand in DMSO so it is maximally concentrated, 100mM works fine. Add enough compound to achieve 2-3 fold excess to your protein, mix and set up. Make sure your final DMSO concentration is ~3%, otherwise chances are you might harm your protein. If you cannot achieve a high enough stock concentration of DMSO to be below the 3% threshold, dilute you protein in the storage buffer to ~1mg/ml. Add compound to 2-3 fold access, incubate and co-concentrate to the desired concentration. That way you avoid the DMSO shock.
Alternatively you could incubate the concentrated protein with the compound solubilized in water for 24-48hr and hope it is soluble and potent enough to get taken up by the protein and then set up your trays. HTH Carsten > -----Original Message----- > From: CCP4 bulletin board [mailto:[EMAIL PROTECTED] > Behalf Of Yue Li > Sent: Tuesday, December 11, 2007 11:55 AM > To: CCP4BB@JISCMAIL.AC.UK > Subject: [ccp4bb] insoluble ligand > > > Hi all, > > I have one ligand which is insoluble in water, and I would like to > co-crystallize it with my protein. Is there any other method > except for > dissolving it in DMSO ? > > Thanks > > Simon > >