To Mix, or To Demix, That Is the Question
Biophys. J., 112, 565–567 (2017)
Harmon, T.S., Holehouse, A.S., Pappu, R.V.
This New & Notable was a pleasure to write, and I think provides a useful high level summary of some really beautiful (albeit complex) work from William Jacobs and Daan Frenkel .
Given the New and Notable is only a couple of pages long I won't go into too much detail, but the general question in the Jacobs et al. paper is, fundamentally, one of expectations; given a multi-component mixture of differently interacting species, what is the expected phase behaviour? The conclusion from this work is that there exist two stable points in the dynamical landscape generated by a complex mixture of species. In one limit (condensation) all the components coalesce into a single dense phase, leaving behind a single dilute phase. In the other limit (partial demixing), a small sub-set of the components phase separate into homogenous or near homogenous dense phases, while the other components remain soluble. This provides a crucial prior that allows the field to think about how Nature deviates from this expected behaviour (or, in many cases does not).
The implications of this work are significant for thinking about the intersection of theory and the experimentally observed phase behaviour in real-life complex multi component systems (e.g. the cytoplasm). Importantly, these conclusions say nothing about either the organization or the dynamics of those phase separated states, meaning work remains to understand how these factors will influence the expected behaviour.
 Jacobs, W.M., and Frenkel, D. (2017). Phase Transitions in Biological Systems with Many Components. Biophys. J. 112, 683–691.