bookmark QMEAN A method for estimating the absolute quality of a single protein structure, i.e. without including additional information from other models or alternative template structures. QMEAN is based on the composite scoring function which evaluates several structural features of proteins. The absolute quality estimate of a model is expressed in terms of how well the model score agrees with the expected values from a representative set of high resolution experimental structures. The resulting QMEAN Z-score is a measure of the ‘degree of nativeness’ of a given protein structure. The Z-scores of the individual components of the composite QMEAN score point to structural descriptors that contribute most to the final score, and thereby indicate potential reasons for ‘bad’ models.