Context: GFP ("green fluorescent protein") is a protein, derived from jellyfish, that does exactly what it says. Cell biologists use gene engineering to attach it to specific proteins or structures in living cells, and then look for the glow under the microscopes to see where these proteins/structures end up. There are a lot of variants of GFP, that are different colors or only fluoresce under certain conditions.
For more context, the idea that any biological protein responds to magnetic fields is (at least slightly) controversial. Our observation (a commonly used, well-known fluorescent protein gets slightly but unmistakably dimmer in response to a handheld magnet) is surprising, but it's straightforward to reproduce.
It's not an immediately useful result, but there's a long history of successfully engineering small effects into big effects in fluorescent proteins. If that's possible here (unproven), we could imagine noninvasive control of arbitrary biological machinery ("magnetogenetics").
Even if it's technologically useless, this observation also raises interesting questions about the effects of magnetic fields on biochemistry. Is this a unique edge case, or an instance of a more general phenomenon? What are the necessary/sufficient conditions for magnetic fields to affect life? Given that MRI is nonlethal, there are bounds on how strong these effects can be... but are they really zero?
