Peak-shape analysis for protein neutron crystallography with position-sensitive detectors

Abstract

In neutron protein crystallography, the use of position-sensitive detectors controlled by a modern data acquisition system permits new approaches to data collection strategies. Instead of dealing with conventional scans, like the θ-2θ scan, that provide an integrated intensity as a function of a rotational parameter, the computer-linked counter can be used to produce a three-dimensional reflection profile. As the crystal steps (Δω) through a reflection, the observed data for each step are stored in an external memory as a function of extent in 2θ and height (y) of a reflection. In this space, the reflection will be a three-dimensional distribution with dimensions determined by such basic geometrical conditions as Δλ, crystal size, mosaic spread, counter-resolution, and beam-collimation parameters. Knowledge of the interaction of these basic parameters will allow the design of optimal beam optics and will permit the delineation of the reflection from the background and permit, therefore, an accurate intensity determination.