Figure 1. Polychromatic Laue X-ray diffraction pattern. The pattern shown is a computational representation of the diffracted X-rays produced from a crystal of isocitrate dehydrogenase using an incident X-ray beam bandpass of 0.95–1.55 Å and a maximum resolution for observed spots of 2.4 Å. For this crystal, which belongs to space group P4₃2₁2, a = b = 105.1 Å, c = 150 Å, more than 50% of the unique diffracted X-rays are collected from a single exposure. Typical exposure time to collect a diffraction pattern is 1 ms.

Figure 2. General methods of intermediate accumulation for time-resolved crystallographic studies. (a) A rapid initiation event, usually a photoreaction, induces the formation of a substrate complex ‘A’ with a rate constant of k_start. The reaction proceeds and encounters a rate-limited intermediate ‘I’ which decays with a rate constant k_cat. The lifetime of the intermediate during this initial reaction event is dictated by k_cat. The occupancy or concentration of I throughout the crystal during this time period is dictated by the initial concentration of A produced by the photoreaction, and by the ratio of k_start to k_cat. (b) A high occupancy, rate-limited, steady-state complex accumulates throughout the crystal as a result of diffusion of substrate into the crystal solvent channels. The occupancy or concentration of the rate-limited intermediate I is a function of the rate of diffusion relative to k_cat, as is the time required to achieve steady state. In principle, the intermediate I can be maintained indefinitely; in practice, the crystal will often display a limited period of stability under multi-turnover conditions.