The word "weak" is, of course, relative. Free energy of crystallization is roughly 1-2 kcal/mole of crystal contacts (I think I carried this number from Sir Blundell's book, but quick look at papers by Peter Vekilov's group seems to confirm it - am I wrong on this?). I think that crystal contacts are still much weaker than any interaction of biological importance (perhaps I am wrong on this one too and there are important biological protein-protein interaction with 10mM affinity, but I doubt that they are many).
On Mon, 2008-06-30 at 10:09 -0400, Patrick Loll wrote: > I hope this isn't too much of a foray into philosophy and semantics, > but can't you argue that the crystals themselves are weak complexes? > And since the energies of crystal contacts are typically very weak, I > would further argue that you should be able to crystallize ANY complex > with an association constant corresponding to energies as low as those > associated with crystal contacts. Of course, it's not guaranteed, any > more than getting a crystal is guaranteed--you need some luck. > > > Of course, it's Monday AM, and I haven't approached my asymptote for > caffeination. Am I talking through my hat? > > > Pat > > > > > On 29 Jun 2008, at 3:36 PM, Derek Logan wrote: > > Hi, > > > > > > Can anyone advise me what is currently the weakest protein-protein > > complex yet crystallised? Google searching turned up a paper from > > the Tromsø crystallography group (Helland et al. 1999, JMB 287, 923– > > 942) in which a complex between beta-trypsin and a P1 mutant of BPTI > > with a Kd of 68 uM was described as belonging to the weakest > > complexes solved to date, but this article was from 1999 and much > > water has passed under the bridge since then. > > > > > > Thanks > > Derek > > _________________________________________________________________ > > Derek Logan tel: +46 46 222 1443 > > Associate professor fax: +46 46 222 4692 > > Molecular Biophysics mob: +46 76 8585 707 > > > > Centre for Molecular Protein Science > > Lund University, Box 124, 221 00 Lund, Sweden > > > > > > > > > > > > > > > > > > > > > > > > --------------------------------------------------------------------------------------- > > Patrick J. Loll, Ph. D. > > Professor of Biochemistry & Molecular Biology > > Director, Biochemistry Graduate Program > > Drexel University College of Medicine > > Room 10-102 New College Building > > 245 N. 15th St., Mailstop 497 > > Philadelphia, PA 19102-1192 USA > > > (215) 762-7706 > > [EMAIL PROTECTED] > > > > -- Edwin Pozharski, PhD, Assistant Professor University of Maryland, Baltimore ---------------------------------------------- When the Way is forgotten duty and justice appear; Then knowledge and wisdom are born along with hypocrisy. When harmonious relationships dissolve then respect and devotion arise; When a nation falls to chaos then loyalty and patriotism are born. ------------------------------ / Lao Tse /
