🚀 go-pugleaf

Henry Spencer writes:

> McDonnell-Douglas is selling its shuttle-borne biochemical electrophoresis
> equipment to NASA, for a pittance.

I'm not surprised this has happened.  I've read that McD-D considered
CFE because, among other reasons, they thought no competing process
could be developed in 5 years (this more than 5 years ago).

Recall that continuous flow electrophoresis is a process where a stream
of protein mixture is injected into a slab of flowing buffer fluid.  An
electric field applied across the slab causes proteins to migrate
laterally at a rate dependent on their charge and size.  At the other
end of the cell the stream has been separated and is collected in a series
of outlets.

Microgravity is supposed to help this process, for a number of reasons:

  - Most important, the protein mixture can be made to have a higher
    density than the buffer fluid.  In gravity, it slumps and disrupts the
    flow.  This increases throughput by a factor of 100.

  - Higher electric fields and thicker cells can be used in microgravity,
    because heating due to ionic currents does not cause convection.  This
    increases the throughput by another factor of 5 to 10.

However, I don't understand why you can't cleverly avoid these
problems in gravity.  Naively, I would have thought that you could
avoid thermal convection by running the equipment horizontally, and
cooling it on the bottom.  The difference in density between the
protein mixture and the buffer fluid could be addressed by making the
buffer fluid more dense (for example, by mixing in a carrier protein
that can be easily separated afterwards), or by setting up a vertical
density gradient.

> The protein-crystal growth experiment aboard Discovery came up with
> bigger and better crystals than yet produced on Earth.  Several more
> drug companies have joined the sponsoring consortium for the next
> flight, on STS-29 in Feb.

I previously was skeptical of this application, but I was wrong, I
think. I've read that drug companies are willing to spend $100-200K
for good crystals of particular proteins, and drug company R&D budgets
are in the billions of dollars.  If microgravity really does let one
make protein crystals that give better diffraction paterns, launch
costs would be less important than flexibility in scheduling and short
turnaround time.  Clearly a niche for a private sector launcher.

	Paul F. Dietz
	dietz@cs.rochester.edu