Correlation Search with Constrained Solution

Volkmann and Hanein (1999) start with the premise that the maximum of the cross-correlation search rarely gives the best solution. Rather, considering the statistics of the cross-correlation term defined in equation (3.15), an entire neighborhood of the peak should be considered as a set of possible solutions, all having different rotations and shifts. Thus, the outcome of the search is not just a single position, but a solution set, from which the most plausible solution can be selected only by applying additional constraints. These constraints are provided by the consistency with data available from bioinformatics. For instance, those solutions are prohibited that would lead to direct steric clashes or clashes considering a van der Waals' molecular envelope. Consultation of such rules gives not only ''permissible'' or ''nonpermissible'' verdicts, but can also provide a scoring for each member of the solution set, resulting in a probability distribution. The maxima of this distribution can then be taken as belonging to the most plausible, energetically favored solutions.

This approach is promising but would seem to require more study to ascertain the appropriateness of the statistical models underlying the definition of the solution set. Applications of this method have been in the docking of various actin-binding molecules to actin: fimbrin (Hanein et al., 1998), myosin (Volkmann et al., 2000), and the Arp2/3 complex (Volkmann et al., 2001).

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