Dear CCP4BB followers,
We are currently trying to obtain ligand-bound complexes for one of our
proteins by soaking and/or co-crystallisation. We have had prior success for
this protein, but using a different class of ligands. The new ligand (in DMSO)
remains in solution (more or less) when mixed with the
reservoir/cryoprotectant, and the diffraction pattern survives the soaking
nicely. Annoyingly though, all we see are density peaks that match the size of
DMSO and become more pronounced when increasing [DMSO] (to help solubilisation
of the ligand). Soaking times varied between minutes to 16 hours. Kd was
measured ( ~ 10 uM) in the solution state.
We have tried pyridine (which keeps the ligand in solution, but kills
diffraction in an instant), and DMF (which doesn't keep the ligand in solution
when mixing with cryoprotectant).
I am wondering whether the community has suggestions for alternative organic
solvents that have been used to solubilise hydrophobic ligands, and are
reasonably gentle to the protein crystal.
Thank you.
Klaus
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Klaus Fütterer, Ph.D.
Reader in Structural Biology
Undergraduate Admissions
School of Biosciences P: +44-(0)-121-414 5895
University of Birmingham F: +44-(0)-121-414 5925
Edgbaston E: k.futte...@bham.ac.uk
Birmingham, B15 2TT, UK W: http://tinyurl.com/futterer-lab
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