Re: [ccp4bb] Can twinning be seen in the diffraction pattern?

PS: For a microscopically visible example in proteins, see the lovely cubic insulin interpenetrating non-merohedral twin crystallized by Madhumati Sevvana (Fig. 11a; thankfully open-access article): Madhumati Sevvana, Michael Ruf, Isabel Uson, George M. Sheldrick and Regine Herbst-Irmer.

[ccp4bb] Modifications to support for SHEET and ligand SITE records in June 2021

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Re: [ccp4bb] Can twinning be seen in the diffraction pattern?

Far as I understand, twins may or may not have macroscopically recognizable features. Macroscopic (and microscopic) features like face angles, reaction on etching, polarization of light, etc. can sometimes indicate twinning for at least a subset of cases, e.g. in diamond, some forms of quartz,

Re: [ccp4bb] Can twinning be seen in the diffraction pattern?

It seems to me that it is legitimate to refer to what you describe as "twinning". That's the difference between merohedral and non-merohedral twinning. What you describe is non-merohedral twinning. In fact twinning has been (re)discovered by most of the biological community after the

[ccp4bb] Postdoctoral position at ICTER in Warsaw, Poland

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Re: [ccp4bb] Can twinning be seen in the diffraction pattern?

Yes Ana, I agree although some non-merihedrals where the accident of cell dimensions mean many spots can overlap but not quite exactly can seem a bit smeary and "multiple. Meridral twins do not usually look multiple - they are usually only revealed by the 2nd moment and other stats.. Eleanor On

Re: [ccp4bb] Can twinning be seen in the diffraction pattern?

Just a short note on this: I often see colleagues using the word “twinning" when referring to a crystal that is actually multiple (not single). I think much confusion arises from this. For me, a twin crystal is the one that looks single under the microscope and only intensity statistics reveal