Friday, July 1, 2016

Astronaut sounds like a fun bench chemistry job

I really enjoyed Sarah Everts' interview in this week's C&EN with Helen Sharman, the first British citizen in space: 
What kinds of experiments did you do on Mir? 
We did a lot of agricultural experiments. They were very interested in growing food in space. And in the way magnetic fields affect plant growth. So how potato roots can be pulled in a certain direction if you have a strong enough magnetic field around them. We also had a miniature lemon tree. We wanted to see if we could keep it alive by supplying all the right gases. It was at the space station for three years but died eventually. We were also growing crystals of the protein luciferase. 
The experiments were fairly foolproof—I’d call us space technicians not scientists. Astronauts don’t invent the experiments. We don’t analyze the data, and by and large, we don’t make conclusions. We send the data down to Earth. But at least when we were carrying out the experiments, my chemistry degree made it easy for me to understand what was going on inside the boxes and what to do if there were problems. 
Can you explain why protein crystals grow better in space? 
Imagine crystallizing something on Earth. As bits of the solute move from the solution into the crystal, that local bit of solution becomes less dense—only very marginally. But it’s enough to effect convection currents in the solution. For strongly ionic solutions, convection doesn’t matter: The ionic bonds are so strong that convection currents don’t get in the way of forming nice ionic crystals. But proteins are big, floppy molecules, often with very weak interactions between the molecules that make up the crystal. Even very small convection currents create dislocations within protein crystals. Bits that aren’t quite right. 
In an orbiting space station, warm air doesn’t rise—you don’t get convection in anything. So there are no convection currents in a solution as crystals are crystallizing. You can grow protein crystals of a much higher quality at an orbiting space station, and you can grow them much bigger.
I wonder if there's ever been any efforts to launch a robotic crystallization laboratory? 

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