MOLECULAR REPLACEMENT USING DNA HELICAL SYMMETRY

The efficiency of molecular-replacement methods in the structure analy sis of B-DNA is markedly increased if a knowledge of the structural pr operties and helical symmetry of B-DNA is incorporated into molecular- replacement procedures. The separation of the most significant or most robust parameters, such as the location of helices in the unit cell, from the less well defined parameters, such as rotation around the hel ix axis, further improves the reliability of molecular replacement and avoids frameshift errors in the positioning of the model. This approa ch has been applied successfully to solve novel structures of four B-D NA decamers in various space groups.