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<td>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</td>
 
<td>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</td>
 
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<td>Nextal Classics #6
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= Hampton Crystal Screen #24</td>
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<td>0.2M CaCl2, 0.1M Na acetate pH4.6, 20% isopropanol</td>
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<td>20 mM Tris, 5 mM DTT </td>
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<td>Yes</td>
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<td>Nice-looking crystals observed for two different proteins.  I suspect DTT may play some part.</td>
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