On the use of low-resolution data for translation search in molecular replacement

Low-resolution reflections (approximately 15 Angstrom and lower) are very useful for the translation search in molecular replacement because they are less sensitive to model errors compared with the traditionally used reflections of resolution 4-10 Angstrom. At low resolution, however, the contribution from the bulk solvent is quite significant and corresponding structure factors calculated from a macromolecular model cannot be compared with experimental values if this contribution is neglected. The proposed method provides a way of fast translation searches where low-resolution reflections are taken into account. Test calculations using several experimental data sets show a dramatic improvement in the signal after the bulk-solvent correction and low-resolution reflections were included in the calculation; this improvement allowed unambiguous identification of the solution.