Does the cyanobacterial KaiABC clock run near minimal cost?
In plain words
Three proteins called KaiA, KaiB and KaiC keep a 24-hour rhythm in a test tube by burning ATP. The question is whether they spend close to the least energy that physics allows for their precision.
Precise statement
For the reconstituted KaiABC oscillator (period $\sim 24\,\mathrm{h}$; ATP use of approximately 15 ATP per KaiC monomer per day), measure the phase-diffusion constant and the total entropy production per period, and compare with the thermodynamic uncertainty relation $\operatorname{Var}(N_T)/\langle N_T\rangle^2 \ge 2 k_B/\Sigma_T$ for the cycle count $N_T$ over time T with entropy production $\Sigma_T$. Answer: the ratio of measured cost to the bound.
What would settle it
Simultaneous measurement of phase diffusion and ATP hydrolysis rate in the reconstituted oscillator at fixed protein concentrations.
Status in the literature
A 2015 model (Cao, Wang, Ouyang, Tu) linked KaiABC precision to its free-energy consumption; a direct test against a rigorous bound is not established.