720 is not an impressive size for a stable interface, but it may do depending on molecule size and exact chemistry of the interface (h-bonds, salt bridges, disulphides, charges etc etc). Everything is subject to chemical environment and concentration, as usual. For these entries, PISA gives dissociation free energy of -1 kcal/mol. Given some +/- 5 kcal/mol estimated (guessed) accuracy of PISA, this may or may not be a stable thing. And yes, it has about 70-80% chances to be simply an artefact of crystal packing, according to some sort of derivations that I did in 2nd PISA paper in J.Comp.Chem. in January last year.
Having said all this, PISA is not an oracle and does not pretend to be correct in 100% of instances. Eugene. On 5 Sep 2011, at 10:14, Eleanor Dodson wrote: > Like Jan, I find it very useful to sort out the clear cut cases. Otherwise it > is easy to get things wrong.. > > But isnt a buried surface area of 720 rather small for a stable interface? > If there is other confirming evidence like 2 diff space groups then you feel > more secure!! > > On 09/01/2011 02:27 PM, Yuri Pompeu wrote: >> This is regarding Ethan´s point, particularly: >> >2) the protein has crystallized as a monomer even though it >> >[sometimes] exists in solution as a dimer. The interface >> >seen in the crystal is not the "real" dimer interface and >> >thus the PISA score is correct. >> I see the same exact interface in a crystal of a close homologue that >> belongs to a different space group (hexagonal vs tetragonal system)
