Sticky crystals: Difference between revisions

Sticky crystals (edit)

Revision as of 21:44, 3 February 2009

1,013 bytes removed , 3 February 2009

no edit summary

Savvas

9

edits

@@ Line 3: / Line 3: @@
 OPERATE ON THE PLASTIC RATHER THAN ON THE CRYSTAL!
------------------------------------------------------------------------
+--------------------------------------------------
--I dig the microtool into the plastic as close as I can get to the crystal without touching the crystal. Usually a small deformation of the plastic causes the crystal to pop off intact.
+Take a sturdy needle (like one of the microneedles from a Hampton kit, or a very thin syringe needle, or an accupuncture needle) and stick the needle into the plastic a bit away from the crystal. Push hard. If you’re using polarizers, you may be abe to visualize the stress forces in the plastic by the shifting of the colors. The basic idea is to stress the plastic under the crystal without touching the crystal in any way. By digging and twisting, one can generate little movements across the plastic which can be enough to free the crystal. Sometimes you have to push quite hard, and to wiggle the needle a bit. Beware, however, as the needle can slip and ruin the crystallization drop.
--I have had similar problems with crystals sticking to the plastic of the crystallisation plates (96-well Grenier plates). I use an acupuncture needle and dig into the plastic right next to the crystal, directing the needle below the crystal. By digging and twisting, you can generate little movements across the plastic which can be enough to free the crystal. If you slip, you end up playing golf with your crystals, but with a steady hand, it has worked well for me, though I guess it might be quite dependant on the strength of the plastic of the plate. Worth trying though if you have crystals.
--Take a sturdy needle (like one of the microneedles from a Hampton kit or a very thin syringe needle) and (while observing the whole thing under a scope) stick the needle into the plastic a bit away from the crystal. Push hard. If you’re using polarizers, you may be abe to visualize the stress forces in the plastic by the shifting of the colors. The basic idea here is to stress the plastic under the crystal w/o touching the crystal in any way. In my case the bloody things just popped off. Sometimes you have to push quite hard, and to wiggle the needle a bit – and beware, they can slip and ruin your drop. But this really worked quite well!
 COAT THE CRYSTALLIZATION SURFACE WITH A THIN LAYER OF GREASE
 -------------------------------------------------------------------------------------
--Additionally, once I realized this was going to be a long term problem, I started coating the sitting drop depressions with a thin layer of vacuum grease.  The crystals just slid right off the grease and I never saw any changes in the diffraction data to suggest the grease was giving me issues.
+If working with the 'sitting-drop' geometry, one can coat the sitting drop depressions with a thin layer of vacuum grease. You only need a very thin layer of the grease (i.e. keep wiping off with a KimWipe until the grease is almost completely gone). Upon crystal harvesting, the crystals will have the tendency to slide right off the grease.
--You only need a very thin layer of the grease (i.e. keep wiping until its almost completely gone) and it usually has no affect on the crystallization.
+One may opt for Vaseline or petroleum jelly rather than silicone-based grease.
--Another approach is to grease the wells of the plate.  If you then gently warm and melt the grease (use Vaseline or other petroleum jelly rather than silicone grease) it will set almost clear.  This is sometimes used with microbatch.
 COAT THE CRYSTALLIZATION SURFACE WITH SILICON
 ----------------------------------------------------------------
-You can try various siliconizing fluids.  Hampton used to sell one called Aquasil which you mix up in water.  This will not melt the plastic as eg. Repelcote will.
+You can try various siliconizing fluids such as AquaSil (Hampton Research).  Such a product will not melt the plastic of the crystallization plate as opposed to eg. Repelcote.
 CHANGE CRYSTALLIZATION PLATE