The properties of (2Fo - Fc) and (Fo - Fc) electron-density maps at medium-to-high resolutions

Acta Crystallographica. Section D, Biological Crystallography
A MinichinoJ R Helliwell

Abstract

This paper reports on the efficacy of (F(o) - F(c)) versus (2F(o) - F(c)) electron-density maps at 3.2 A resolution. Firstly, a study is reported of a simple truncation at 2.3 and 3.2 A of the 1.6 A resolution crystal structure of concanavalin A at room temperature [Emmerich et al. (1994), Acta Cryst. D50, 749-756] with 149 known bound water molecules. Secondly, the concanavalin A 1.6 A resolution model was re-refined but with the data truncated to 3.2 A. In a similar evaluation, these procedures were repeated for the apocrustacyanin A1 cryotemperature 1.4 A resolution model [Cianci et al. (2001), Acta Cryst. D57, 1219-1229]. Maps at 1.4, 2.3 and 3.2 A resolutions were first generated and the structure was then re-refined at 3.2 A and additionally at 2.3 A resolution. The results on concanavalin A show that the number of bound water molecules that are resolved decreases by two thirds from 1.6 to 3.2 A, but that key structural waters, for example at the transition metal and the calcium ion, are still resolved in the (F(o) - F(c)) map but not in the (2F(o) - F(c)) map. For apocrustacyanin A1, the results with these two difference maps were less clear-cut. Two key structural bound waters (w93 and w105) were selected that had been ...Continue Reading

Citations

May 1, 2007·Archives of Biochemistry and Biophysics·Aaron P BenfieldStephen F Martin
Dec 19, 2020·Protein Expression and Purification·Chi ZhangAntti Moilanen

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