Dear Rex, These issues of energy overlaps are addressed in theory, for either diffraction probe, in Cruickshank, Helliwell and Moffat 1987 Acta Cryst, and also by the same authors in 1991 Acta Cryst for spatial overlaps, and in practice in eg Ren et al JSR 1999 and Nieh et al JSR 1999. Basically the predominance of singlet reflection Laue spots is a consequence of the probability of prime numbers and, where you do have energy overlapped spots, the effectiveness of energy overlaps' deconvolution arises where you have symmetry equivalents and/or multiple occurrences of the same hkl, which usually one does. The low resolution reflections in particular have a higher probability of occurring in multiples and thus are mainly the ones that require the deconvolution of intensities ie of the fundamental and its harmonic(s). The extracted intensities so obtained are actually of a very good precision. A high completeness through all the resolution range is overall readily achievable with Laue.
Re point 2. These issues, and advantages, are explored in Blakeley et al 2004 PNAS which features freezing of such large crystals through to protein and ordered solvent, which there is more of, model refinement. Losses of diffraction quality for freezing attempts with bigger crystals in our experience is worse though ie more probable than with small crystals, and so if you don't have some sort of supply, would certainly be off putting, but obviously it's doable. Also it is my belief that as experience grows so will such procedures improve and the scope thereby widen, encompassing for example freeze trapping studies with neutrons as probe. Greetings, John Prof John R Helliwell DSc On 21 Sep 2011, at 10:52, REX PALMER <rex.pal...@btinternet.com> wrote: > Re Neutron Data Collection: > 1. What are the limits to data set completeness imposed by a Laue experiment > versus those of monochromatic data collection? > 2. What problems are caused by flash freezing the larger protein crystals > used for neutron data collection which do not occur for X-ray data collection > ie because smaller crystals can be used. > Any help will be greatly appreciated. > > Rex Palmer > http://www.bbk.ac.uk/biology/our-staff/emeritus-staff > http://rexpalmer2010.homestead.com
