Fig. S9.

Increase of the radius of gyration of the bare protein $\mathrm{\Delta }{R}_g^{\text{Prot}}$, computed from the atomic coordinates of the protein atoms (including heme) after photodissociation, and averaged over $\sim$ 10,000 simulations of the small simulation system. Absorption of additional photons was simulated as described in Materials and Methods. $\mathrm{\Delta }{R}_g^{\text{Prot}}$ was scaled by ${\rho }_p/\left({\rho }_p-{\rho }_{\text{bulk}}\right)$ (${\rho }_{\text{bulk}}=334$ e⋅nm⁻³, ${\rho }_p=440$ e⋅nm⁻³) to allow direct comparison with the radius of gyration computed from a Guinier analysis. See Materials and Methods for details. Including the CO atoms yields $\mathrm{\Delta }{R}_g^{\text{Prot}}$ curves that are nearly identical to the curves shown here, suggesting that CO hardly contributes to $\mathrm{\Delta }{R}_g^{\text{Prot}}$. The zero photon curve (blue) fluctuates within the statistical uncertainty up to 5 ps. For times larger than 5 ps, small systematic patterns appear, presumably due the onset of temperature and pressure coupling at 5 ps (SI Materials and Methods).