A Time-Dependent Density Functional Theory Investigation of the Spectroscopic Properties of the β-Subunit in C-Phycocyanin
journal contributionposted on 21.09.2006, 00:00 by Yanliang Ren, Jian Wan, Xin Xu, Qingye Zhang, Guangfu Yang
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 π electron excitation of the pyrrole rings and the shoulder peak as arising from the charge transfer from the asparate residue to PCBH+. The satisfactory agreement between theory and experiment suggests that Förster resonance theory prevails such that energy transfer occurs from βs (β-155) to βf (β-84).