Evaluation of macromolecular electron-density map quality using the correlation of local r.m.s. density.
It has recently been shown that the standard deviation of local r.m. s. electron density is a good indicator of the presence of distinct regions of solvent and protein in macromolecular electron-density maps [Terwilliger & Berendzen (1999). Acta Cryst. D55, 501-505]. Here, it is demonstrated that a complementary measure, the correlation of local r.m.s. density in adjacent regions on the unit cell, is also a good measure of the presence of distinct solvent and protein regions. The correlation of local r.m.s. density is essentially a measure of how contiguous the solvent (and protein) regions are in the electron-density map. This statistic can be calculated in real space or in reciprocal space and has potential uses in evaluation of heavy-atom solutions in the MIR and MAD methods as well as for evaluation of trial phase sets in ab initio phasing procedures.
Terwilliger
T C
TC
Structural Biology Group, Los Alamos National Laboratory, Los Alamos, NM 87545, USA. terwilliger@lanl.gov
Berendzen
J
J
D001426:Bacterial Proteins / Q000737:chemistry; D003198:Computer Simulation; D018360:Crystallography, X-Ray / Q000379:methods*; D046911:Macromolecular Substances; D011506:Proteins / Q000737:chemistry*; D012240:Rhodococcus; D012984:Software; D012997:Solvents / Q000737:chemistry
D001426:Bacterial Proteins; D046911:Macromolecular Substances; D011506:Proteins; D012997:Solvents