By using time-dependent density functional theory combined with the polarizable continuum model, a satisfactory assignment of the absorption and circular dichroism spectra and energy transfer flow of the β-subunit in C-phycocyanin (C-PC) was achieved when the protonation of β-84 and β-155 phycocyanobilin (PCB) and their interaction with the protein moiety in C-PC have been taken into account. We attribute the main peak for both β-84 and β-155 as arising from the πelectron excitation of the pyrrole rings and the shoulder peak as arising from the charge transfer from ...
