The minimum probable values of residuals for the best centrosymmetric model of an approximately centrosymmetric crystal

Abstract

502MEAN ERROR IN ATOMIC POSITIONS described in § 4. In such hypothetical cases, I FNI will be free from errors of observation. However, when one uses the observed overall value of an R index for finding (Izarl), one must remember that the experimental errors in I Fobsl would also contribute to the overall value of the R index. Owing to this one has to note the following two points in estimating (Izarl)

PROCHECK: a program to check the stereochemical quality of protein structures

“…a Luzzati plot (Luzzati, 1952), a era plot (Read, 1986), or the R indices and tables of Elango & Parthasarathy (1990). Another measure is the 'free R value ', or R,~ 'e, of Briinger (1992), which is a means of calculating an unbiased R factor.…”

Error Estimates of Protein Structure Coordinates and Deviations from Standard Geometry by Full-Matrix Refinement ofγB- andβB2-Crystallin

“…More recent attempts to estimate errors have included: the 'residue R factor' of Jones et al (1991); the tabulated R indices of Elango & Parthasarathy (1990); the refinement protocol of Carson et al (1994) which uses temperature factors, real-space fit residuals, geometric strains, dihedral angles and shifts from the previous refinement cycle; the 'discriminator' of Sevcik et al (1993) which assesses the likely errors on each atom in terms of its temperature factor divided by its electron density in the final 2IF,,[ -IF,.I map, or U/p where ,o is the electron density; an empirically derived six-parameter equation of Stroud & Fauman (1995), and the use of the diagonal elements of the inverse normal matrix in a final cycle of unrestrained least-squares refinement to give an estimate of the radial errors in atomic positions (Holland et al, 1990).…”