A normalised scale for structural genomics target ranking: The OB-Score

Target selection and ranking is fundamental to structural genomics. We present a Z-score scale, the “OB-Score”, to rank potential targets by their predicted propensity to produce diffraction-quality crystals. The OB-Score is derived from a matrix of predicted isoelectric point and hydrophobicity values for nonredundant PDB entries solved to ⩽3.0 Å against a background of UniRef50. A highly significant difference was found between the OB-Scores for TargetDB test datasets. A wide range of OB-Scores was observed across 241 proteomes and within 7868 PfamA families; 73.4% of PfamA families contain ⩾1 member with a high OB-Score, presenting favourable candidates for structural studies.