  The microscopic origins of terahertz (THz) vibrational modes in biological
systems are an active and open area of current research. Recent experiments
[Physical Review X 8, 031061 (2018)] have revealed the presence of a pronounced
mode at $\sim$0.3 THz in fluorophore-decorated bovine serum albumin (BSA)
protein in aqueous solution under nonequilibrium conditions induced by optical
pumping. This result was heuristically interpreted as a collective elastic
fluctuation originating from the activation of a low-frequency phonon mode. In
this work, we show that the sub-THz spectroscopic response emerges in a
statistically significant manner (> 2$\sigma$) from such collective behavior,
illustrating how specific THz vibrational modes can be triggered through
optical excitations and other charge reorganization processes. We revisit the
theoretical analysis with proof-of-concept molecular dynamics that introduce
optical excitations into the simulations. Using information theory techniques,
we show that these excitations can induce a multiscale response involving the
two optically excited chromophores (tryptophans), other amino acids in the
protein, ions, and water. Our results motivate new experiments and fully
nonequilibrium simulations to probe these phenomena, as well as the refinement
of atomistic models of Fr\"ohlich condensates that are fundamentally determined
by nonlinear interactions in biology.
