title: A time dependent density functional theory study of alpha-84 phycocyanobilin chromophore in C-phycocyanin.
abstract: The optical characteristics of absorption and circular dichroism (CD) spectroscopy of an alpha-subunit of C-phycocyanin (C-PC) were investigated by using time dependent density functional theory (TDDFT) combined with the polarizable continuum model (PCM). When the protonation of alpha-84 phycocyanobilin (PCB) and its interaction with the protein moiety in C-PC have been taken into account, satisfactory assignment of the absorption and CD spectra of alpha-84 PCB can be achieved. The TDDFT-PCM calculations conclude that in the visible absorption region the main peak arises from the pi electron excitation of the pyrrole rings and the shoulder peak comes from the charge transfer from Asp87 (a nearby amino acid residue) to PCBH(+).
authors.affiliation: Key Laboratory of Pesticide and Chemical Biology (CCNU), Ministry of Education and Department of Chemistry, Central China Normal University, Wuhan 430079, China. jianwan@mail.ccnu.edu.cn
authors.forename: Jian
authors.initials: J
authors.lastname: Wan
authors.forename: Xin
authors.initials: X
authors.lastname: Xu
authors.forename: Yanliang
authors.initials: Y
authors.lastname: Ren
authors.forename: Guangfu
authors.initials: G
authors.lastname: Yang
mesh_terms: D002942:Circular Dichroism; D000458:Cyanobacteria / Q000737:chemistry; D004563:Electrochemistry; D008956:Models, Chemical; D008958:Models, Molecular; D052980:Phycobilins / Q000737:chemistry*; D010798:Phycocyanin / Q000737:chemistry*; D011506:Proteins / Q000737:chemistry; D000461:Rhodophyta / Q000737:chemistry; D013056:Spectrophotometry, Ultraviolet
chemical_list: D052980:Phycobilins; D011506:Proteins; C520067:alpha-84 phycocyanobilin; D010798:Phycocyanin; C011069:phycocyanobilin