No offense intended, but NMR is not a structure determination method. One _estimates_ what a structure _might_ look like if such and such "restrainoconstraints" applied. We always speak of how undetermined our crystallographic data are, how poor of an estimate is our R/R-free. Shall we even discuss how few restraints/constraints are used in NMR structure "determination"? What is the criterion for NMR model accuracy? The "tightness" of the ensemble? How quantitative is that?
Well, maybe NMR has advanced so far now that the arguments outlined above are now outdated. It would be great if a good up-to-date summary could be pointed out to those living in the dark ages. Petr ________________________________________ From: CCP4 bulletin board [CCP4BB@JISCMAIL.AC.UK] on behalf of Jacob Keller [j-kell...@fsm.northwestern.edu] Sent: Monday, May 23, 2011 4:07 To: CCP4BB@JISCMAIL.AC.UK Subject: Re: [ccp4bb] Crystal structure and NMR structure I think calmodulin is a classic example, in all its forms (I believe that there are both NMR and crystal structures for all of these): +/- calcium, +/- peptide. Especially the no-peptide +/- calcium forms differ pretty substantially. The calcium-bound no-peptide structures are particularly interesting, as it seems that the NMR structure is much more plausible (take a look if you don't believe me--the xtal structure has a really extended alpha helix, which it seems to me would be bending all over the place in solution). And yet, the crystal structure was solved at 1.0 Ang. Now, assuming that the NMR structure is really a truer picture of the structure in solution, this contradicts a premise which always seemed reasonable to me, that as resolution increases, the model more accurately represents the protein as found in solution. I guess the bottom line is that resolution does not necessarily imply a better picture of the molecule as it functions physiologically, but simply means that the crystallography worked out better. Do others agree with this, that resolution implies little about the physiological veracity of the model? Jacob On Sat, May 21, 2011 at 4:03 AM, Chen Guttman <guttm...@bgu.ac.il> wrote: > Here you go: > http://www.ncbi.nlm.nih.gov/pubmed/12015150 > Domain swapping of Cyanovirin. > Chen > > --- > Chen Guttman > The Zarivach laboratory for Macromolecular Crystallography > Building 39, Room 009B > Ben-Gurion University of the Negev > POBox 653 > Zip Code 84105 > Beer-Sheva > Israel > http://lifeserv.bgu.ac.il/wb/zarivach > Tel. +972-8-6479519 > Fax. +972-8-6472970 > > > On Sat, May 21, 2011 at 08:34, Vandu Murugan <wandumuru...@gmail.com> wrote: >> >> Dear all, >> I would like to get some information on proteins where there is >> conformation/structural change between the crystal structure and solution >> structure of the same protein. Do anybody came across such situations? >> Thanks in advance.. >> >> cheers, >> Vandu > > -- ******************************************* Jacob Pearson Keller Northwestern University Medical Scientist Training Program cel: 773.608.9185 email: j-kell...@northwestern.edu *******************************************
