Hi, You're working with a very 'rich' crystallization condition. It probably was supersaturated or close to super-saturated with respect to something, and that something crashed out on the surface (where liquid contacted air) forming a crust. Your loop (while perfectly clean) can also be the source of nucleation. Just a mere act of opening a drop can cause phenomena like this one. How old was your drop (older partially evaporated drops tend to do this more often)?
Sometimes it's possible to slow this crust formation down by coating the drop with a film of oil, as soon as you open the reservoir. I would also recommend avoiding complex buffers like that one unless there's literally no other way to grow your crystals - there's a lot of inherent trouble (especially with phosphate). Artem On Thu, Nov 25, 2010 at 8:45 AM, Rick <mbp08...@sheffield.ac.uk> wrote: > Dear CCP4 > > I looped a v.thin rod emerging from a cluster of v.thin rods that grew in > 29%PEG1500 and 0.1M SPG buffer at pH7.5 (succinic acid, sodium dihydrogen > orthophospate and glycine). The loop i used had been washed more than 10 > times with deionised water (so assumed as 'clean'). The crystals had grown > at 17degreesC, and looped out probably just below room temperature (~20-23 > degreesC). When transferred to 5% glycerol cryo-buffer the crystal > disintegrated (maybe due to glycerol being an unfavourable addition to the > mother-liquor). When i looked back at the original cluster-containing drop, > a very tough shell had formed over the surface of the drop, from which > chunks could be dug out...the nearest analogy is maybe like when you > blow-torch sugar on top of creme brulee, and have to crack it with your > spoon. The crystals within had also disintegrated. Any clues to what might > have caused this very tough shell to form, and maybe how to deal with it? > > Much appreciated > > Rick Salmon
