I'd try either one of two things:
- see if you can grow them in a (very dilute) gel. Very small volumes should
be achievable, maybe dialysis buttons with 'gel-ed' protein and the surrounding
solution with precipitant. The gel presumably will alter the transport of
various molecules and crystal growth phenomena. Although there are a couple of
papers on this, I don't recall anything particularly outstanding.
- see if you can grow crystals in a capillary that is open on one end, filled
with protein, and set with the open end in a gel with precipitant so the
diffusion can take place very slowly.
There are some papers on these methods, Garcia-Ruiz has done some work in this
area, for example J. Crystal Growth 232 (2001), pp165 but this article only
says that the transport phenomena should be different, but not if and how they
affect crystal growth. Also Acta Cryst. F62 (2006), pp 196 seems to have
something along these lines.
Just my 2 cents worth.
Mark
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Sent: Tue, 5 Dec 2006 11:31 AM
Subject: [ccp4bb]: reducing crystal imperfections
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We have a system where we can produce rod-shaped crystals that show a classic
depletion imperfection--the rods are essentially hollow for most of their
length, suggesting that growth is proceeding in this direction more rapidly
than fresh protein can diffuse into the area (picture a long hexagonal rod with
a perfect conical hole bored into one end, extending for most of the rod's
length).
Simple-minded optimization experiments (e.g., [PEG] vs. [salt] vs. pH) have
clear-cut effects on nucleation, but don't seem to alter crystal shape, which I
interpret as meaning that growth occurs rapidly once nucleation has taken
place.
What are peoples' thoughts on improving the morphology? We're currently
exploring whether additives can selectively poison growth along the long axis,
but I'd be curious to hear other ideas. For example, might gels help, or are
they mainly effective in controlling nucleation?
They ARE pretty cool looking. I wonder if there's a market for nanovases...
Pat
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Patrick J. Loll, Ph. D. (215) 762-7706
Associate Professor FAX: (215) 762-4452
Department of Biochemistry & Molecular Biology
Director, Biochemistry Graduate Program
Drexel University College of Medicine
Room 10-102 New College Building
245 N. 15th St., Mailstop 497
Philadelphia, PA 19102-1192 USA
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