Excerpt

Cells  occupy  an  unusual  position  in  the  grand  scale  of  things,  not truly  atomic,  but  not  truly  macroscopic  either.  For  example,  the smallest bacterial cells are composed of millions of atoms, yet certain macromolecules, such as the ribosome, exist in very small quantities (e.g., there are < 100 ribosomes for the smallest bacteria) (Kempes et al. 2017). This discreteness has downstream consequences, for example, as the intrinsic noise associated with randomly splitting a small pool of molecules into two daughter cells. In describing the physics of cells we are caught between the relatively easy physics of single atoms, where quantum mechanics dominates, and the classical physics of macroscopic systems such as hydraulics. This is exactly the point of Robert Laughlin, David Pines, Jörg Schmalian, Branko P. Stojković, and Peter Wolynes in “The Middle Way.” They aren’t just interested in cells but in all “mesoscopic” matter, with a particular interest in biological matter. The advances in condensed matter physics and material science associated with mesoscopic phenomena have been immense since the time that “The Middle Way” was published (e.g., Fish, Wagner, and Keten 2021), but here I want to focus on the biological aspects of this foundational paper, where the mesoscopic is relevant to everything from protein folding to the structure of tissues in multicellular organisms. Indeed, the mesoscopic is still at the heart of the ongoing revolution occurring in biological matter, both from the perspective of detailed dynamics and in terms of broad organizing principles and concepts.

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