By applying an advanced hole-burning fluorescence line-narrowing technique, an unexpectedly strong (several-fold) increase of the electron-phonon coupling strength on excitation wavelength through the inhomogenously broadened absorption origin band was first observed for low-temperature organic glass samples doped with biologically relevant chlorin and chlorophyll a molecules. The dependence, which suggests a direct correlation between solvent shift and the electron-phonon coupling, demonstrates great sensitivity of the zero-phonon transitions localized on single chromophores as optical probes of the structure and dynamics of local subnanoscopic environments. (C) 2009 Elsevier B.V. All rights reserved.