[Protein-analysis] Re: NMR vs X-ray : protein structure

Dr Engelbert Buxbaum via proteins%40net.bio.net (by engelbert_buxbaum from hotmail.com)
Wed Feb 28 15:13:30 EST 2007


chuaby from hotmail.com wrote:

> Hi
> 
> I am trying to learn about NMR and X-Ray to find out protein 3D
> structures. I have read from the web that the results from NMR and
> X-
> Ray could be quite different. But i do not have access to some papers
> that discuss about this.

Fortunately, that is usually not the case. Remember, science is about
repeatability, so different methods, when applied to the same problem,
should yield the same result. That is not to say of course that there
can be no differences at all between protein structures in solution and
in crystalls.


> I read that NMR cannot handle large protein well but X-ray requires
> protein to be crystal form. 

By and large that is correct, however, as NMR instruments with ever
stronger magnets come onto the market the MW limit of that technique is
pushed. The web-sites of manufacurers like Brucker should give you more
info. In addition because of high-throughput screening techniques
protein crystallisation is no longer the black magick it used to be.


> I wish to get a feel from practitioners
> what are the relative qualities of each structure determined by these
> 2 methods ? 

You can check that for yourself, protein structures are submitted to the
Brookhaven database in a unified format (.pdb) and can be downloaded
from the internet (http://bip.weizmann.ac.il/oca-bin/ocamain). For those
proteins where both X-ray and NMR structures have been solved you can
directly compare them using a molecular modeling package like DeepView
(http://www.expasy.org/spdbv/) 


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