Automated determination of interhelical angles for protein alpha helices from coordinate data

This study presents a new algorithm for the accurate determination of the interhelical angle for a pair of alpha helices in a protein. The calculation is fully automated, and uses contact map information to determine the location of the interface region for the pair. The accuracy of the algorithm is tested by comparing the results to angles determined manually by observation in a classic paper. After finding contemporary analogies in the PDB for the data sources, the calculated angles were determined to be accurate to within 4.1◦, with a standard deviation of 3.2◦. This algorithm should prove useful to researchers working on protein structure prediction, particularly by means of assembling supersecondary structures.