Control of crystals' direction and position in the drop.

From: Nian Huang
Date: 14 November 2011 21:15


Dear All,
Does anybody find a way to control a crystal's positioning in the drop? I have needle shaped crystals. What I found out is that the vertical positioned crystals always grow much thicker than the crystals laying flatly. But unfortunately, it is a completely random event and only 1% crystals can appear vertically. I have tried different formats of plates and equilibration techniques w/o much success. Any suggestion is highly appreciated.

Nian Huang, Ph.D.
UT Southwestern Medical Center

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From: Frederic VELLIEUX

Hi,

Your email mentions "drop".

What about trying another technique where you do not have "drops", such as the liquid interface diffusion method (in capillaries), or the use of dialysis ? Crystallisation
under oil (injection of the 2 components under "oil") could also be tried.

Fred

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From: Zhijie Li

Hi,

 

Why not give macroseeding a try?

On the other hand, did your try additive screens? You might find something that modifies the growth behavior of your crystals. In some cases simple manipulation of ionic strength could have great effects. I had a crystal that had a long axis, but the crystals grew as cubes - not ideal for crystal aligning for data collection. Then I found that including about 1M of monovalent salts can turn the crystals into rods, with the long axis being parallel with the longest edge of the rod.

 

Zhiijie

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From: MARTYN SYMMONS

Hi there

         one thing I did to get more space for needles in a drop was to make 'book end' coverslips. Your take a plastic covership and with a razor blade you cut obliquely into the plastic to make a 'flap' of the plastic. Then you lever it up to vertical to give a projecting vertical surface. You can then apply the drop to the angle between the flap and the coverslip. This supports the drop so that it does not flatten so much during equilibration. Making the cut takes a bit of trial and error but the plastic coverslips are not that expensive. It certainly gave me some chunkier needles and gave them space to grow upwards. Otherwise they flattened down as the droplet flattened with equilibration and often they 'glued' themselves to the horizontal surface.

        Hope it helps

            Martyn

Martyn Symmons

Cambridge

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From: Nian Huang


Thank you guys. I basically tried almost everything that I can find in the hampton catalogue and in this bulletin, seeding, hanging, sitting, sandwitch drops (which made things worse), temperature, gel, oil batch, and additive screens. Manipulating the crystal with fiber increases the chance to make it grow twin. The "book end" coverslip sounds a fantasic idea. It might be just going to work.

Best,

Nian

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From: MARTYN SYMMONS

Attached is a picture of making the bookend setup - step b. shows the razor levering up the flap from the plastic coverslip  - be careful not to cut right through (I have done that and the drop dries extra quick in such a case) also be careful to apply the protein/well droplet as shown with to the shiny side of the lifted flap. (Apologies for the attachment). 

hope your crystals go well.

Martyn