Ab initio phasing starting from low resolution

Residue-based scattering factors

A glob is defined as a group of atoms in the crystal which can be chosen in various ways. Globs themselves can be used as scattering elements in the theory of structure determination, just as atoms are used at present. In this paper, amino-acid residues are chosen to form globs and empirical formulas for residue-based scattering factors have been developed.

Low-resolution structure determination of Na(+)-translocating NADH:ubiquinone oxidoreductase from Vibrio cholerae by ab initio phasing and electron microscopy

A low-resolution structure of the Na(+)-translocating NADH:ubiquinone oxidoreductase from the human pathogen Vibrio cholerae was determined by ab initio phasing and independently confirmed by electron microscopy. This multi-subunit membrane-protein complex (molecular weight 210 kDa) generates an Na(+) gradient that is essential for substrate uptake, motility, pathogenicity and efflux of antibiotics. The obtained 16 Å resolution electron density-map revealed an asymmetric particle with a central region of low electron density and a putative detergent region, and allowed the identification of the transmembrane regions of the complex.