# Are there any biological systems that separate isotopes? # Are there any biological systems that separate isotopes [[Proteins act chemically, not electrically or physically]] so by default, they don’t interact with different isotopes, which differ from each other only because of the slightly different masses.[^1] However, biology has figured out wonderful ways to do all sorts of counterintuitive things from harnessing electrical signals to using metals to building inorganic (in the chemical sense) structures like bone and shells. It possibly even takes advantage of quantum effects. So it seems not-unreasonable to wonder whether biology takes advantage of different isotopes as well. Normally when we think of isotopes in biology it’s in the context of different concentrations that occur over time because one isotope decays faster (in the case with carbon 14) or because the lighter isotope diffuses slightly faster (in the case of C12/C13 in the CO2 diffusing into plants.) Are there any situations where living systems actually take advantage of isotopic properties? I wonder because if there were biological systems that took advantage of isotopes, they may hint at molecular-scale ways to separate isotopes as opposed to the bulk methods we use today. If you could more efficiently separate isotopes, it would open up many potential applications. [[Isotope separation is hard]] [^1]: hydrogen is the only element small enough that the additional neutrons create differently [Web URL for this note](http://notes.benjaminreinhardt.com/Are+there+any+biological+systems+that+separate+isotopes) [Comment on this note](http://via.hypothes.is/http://notes.benjaminreinhardt.com/Are+there+any+biological+systems+that+separate+isotopes)