Strategy for data collection from protein crystals using a multiwire counter area detector diffractometer

A strategy for data collection using a diffractometer equipped with a multiwire proportional counter is described. Data are collected using an electronic rotation method similar to an earlier developed `still' method. Data are collected as a set of three to 12 or more `runs'. A data collection `run' consists of a consecutive series of hundreds of electronic rotation pictures with ω advanced by a specific amount (from 0.07 to 0.20°, depending on the mosaicity of the crystal) during each picture. Every picture in a run is taken at the same: χ and ϕ setting angles and exposure time. Information on how to extract the intensity data from these electronic rotation pictures is given elsewhere. Here, the only concern is how to choose a set of ω, χ and ϕ angles for defining a set of runs in order to get a complete set of data in a minimum time. First the diffraction geometry is discussed, then the strategy is outlined; finally, some examples are given to illustrate how the strategy is used in some typical protein data collection problems.