Mathematical Biology Seminar Mikhael Semaan, U of U Biology, Wednesday, Feb. 1, 2023 3:05pm in LCB 225 Fluctuations Beyond Detailed Balance in Voltage-Gated Ion Channels Abstract: Systems exhibiting nonequilibrium steady states (NESSs) produce heat in functionally distinct forms: excess, that dissipated during relaxation to steady state; and housekeeping, that dissipated to maintain the steady state conditions. Building on and extending previous work, we derive and showcase a trajectory class fluctuation theorem (TCFT) for fully general nonequilibrium systems. As corollaries, we highlight connections to two separate stochastic-dynamical Second Laws: one for excess work---most analogous to its equilibrium counterpart---and one for housekeeping heat, which is unique to the NESS setting. Each of these Second Laws alone are statistically true but can be violated by individual realizations. Using the TCFT and taking Na and K ion channel models as examples, we then show how under realistic action potential driving both of these Second Laws are often violated---even by relatively likely trajectories---and taxonomize the rich biophysical behaviors this implies, to which strictly ensemble-based analyses are blind. The generality of our methods thus gives a prescription for uncovering novel thermodynamic functionality in mesoscopic complex systems. Related paper: https://journals.aps.org/pre/abstract/10.1103/PhysRevE.106.044410