Conditions prone to salt crystallization
For some background information please see I have crystals, but are they salt?.
This list shall not include instances when significant drying of the drop occurred. This list should not be taken to mean that the given conditions always produce salt crystals, but they apparently sometimes do.
|Screen and #||Condition||Protein buffer||Confirmed by diffraction||Signature and comment|
|Hampton PEG/ion #1||0.2M NaF, 20% PEG3350, pH7.1||10mM Tris pH7.5, 150mM NaCl||yes||I've seen this condition produce salt crystals at least twice.--Ed 16:18, 23 May 2008 (CEST)
Ditto - NaF has caused me trouble many times - buyer beware! DaveB 11:01, 24 May 2008 (CEST)
Plate 3MembFac & Natrix equivalent
|1M Ammonium Sulfate, 0.1M Sodium Acetate||25mM NaPO4 pH8, 150mM NaCl||yes||Crystals reproduced with proteins and with buffer alone at least twice --Emeric.gueneau 18:21, 16 July 2008 (CEST)|
|Qiagen/Nextal Anions #5 and #6||0.3 M and 0.6 M NaF in NaOAc pH 4.6||20mM Hepes pH7.5, 150mM NaCl||yes||Gives hexagon shaped crystals every time- see line one - beware with NaF --Tom Brett 15:35, 23 July 2008 (CEST)|
|Hampton Crystal Screen #38||0.1 M Hepes pH 7.5, 1.4 M Sodium Citrate||no||Sodium Citrate crystallizes at cold room temp|
|JCSG+ #1 (A1)||0.2M Li2SO4, 0.1M NaOAc pH 4.5, 50.0% v/v PEG-400||No||Mixture must be made by adding water first, else precipitates. Also, crystallizes/precipitates with 10mM CaCl in protein buffer, perhaps even less. Others report needle crystals in well solution.|
|Hampton stockoptions salt as additive||NaF >0.24M, 100mM sodium citrate pH<5.6||20 mM Tris, 150 mM NaCl, 5 mM DTT||Yes||I would expect NaF to be more soluble at low pH (if anything) because of a secondary equilibrium with HF. Nothing in the reservoir, only in the drop; anything under 5.6 gives a few hexagons. If equilibration is slow it will give thick birefringent rods. I'm thinking even minimal contamination by phosphate could give rise to something like fluorapatite, since NaF crystals would be cubic I would think. I have also seen higher concentrations of ammonium fluoride cause the drop to spread all the way over the cover slip and give rise to concentric rings of hexagons (NH4F is actually a hexagonal crystal though as opposed to NaF). Glass etching due to insufficient siliconization? Anyway, beware fluorides in general|
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