Automated matching of high- and low-resolution structural models

A method is presented for automated best‐matching alignment of three‐dimensional models represented by ensembles of points. A normalized spatial discrepancy (NSD) is introduced as a proximity measure between three‐dimensional objects. Starting from an inertia‐axes alignment, the algorithm minimizes the NSD; the final value of the NSD provides a quantitative estimate of similarity between the objects. The method is implemented in a computer program. Simulations have been performed to test its performance on model structures with specified numbers of points ranging from a few to a few thousand. The method can be used for comparative analysis of structural models obtained by different methods, e.g. of high‐resolution crystallographic atomic structures and low‐resolution models from solution scattering or electron microscopy.