2q4w

[[Image:2q4w.jpg|left|200px]]<br /><applet load="2q4w" size="450" color="white" frame="true" align="right" spinBox="true"

==Overview==

X-ray crystallography typically uses a single set of coordinates and B, factors to describe macromolecular conformations. Refinement of multiple, copies of the entire structure has been previously used in specific cases, as an alternative means of representing structural flexibility. Here, we, systematically validate this method by using simulated diffraction data, and we find that ensemble refinement produces better representations of, the distributions of atomic positions in the simulated structures than, single-conformer refinements. Comparison of principal components, calculated from the refined ensembles and simulations shows that concerted, motions are captured locally, but that correlations dissipate over long, distances. Ensemble refinement is also used on 50 experimental structures, of varying resolution and leads to decreases in R(free) values, implying, that improvements in the representation of flexibility observed for the, simulated structures may apply to real structures. These gains are, essentially independent of resolution or data-to-parameter ratio, suggesting that even structures at moderate resolution can benefit from, ensemble refinement.

2Q4W is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Arabidopsis_thaliana Arabidopsis thaliana] with FAD as [http://en.wikipedia.org/wiki/ligand ligand]. Active as [http://en.wikipedia.org/wiki/Cytokinin_dehydrogenase Cytokinin dehydrogenase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=1.5.99.12 1.5.99.12] Full crystallographic information is available from [http://ispc.weizmann.ac.il/oca-bin/ocashort?id=2Q4W OCA].

 

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