Dear Crystallographers, Based on some data sets I have looked at and anecdotal-type evidence here and there I have gotten the impression that detwinning does not help in structure solution. (Please let me know if you have a case where detwinning saved the day.) Is there a clear answer to this enigma anywhere, to anyone's knowledge? Wouldn't it seem that *any* detwinning would be better than *no* detwinning? I understand that the errors explode as one approaches 50% twins and does detwinning, but still, I don't think one *loses* information by detwinning, right? Take the case of a 33% twin: since the twin-reflections are on average about half the intensity of the non-twin, and since they are generally not correlated in intensity, isn't this like having noise added at 50% of the measured intensity? So why does detwinning make things worse generally? Is there something wrong in the assumptions underlying the detwinning algorithm, or perhaps something about the calculation that throws things off?
A related sub-enigma: why is MR generally immune to twinning, but anomalous methods are susceptible? All the best, Jacob Keller ******************************************* Jacob Pearson Keller, PhD Research Scientist HHMI Janelia Research Campus / Looger lab Phone: (571)209-4000 x3159 Email: kell...@janelia.hhmi.org<mailto:kell...@janelia.hhmi.org> *******************************************
