title: Protein-ligand structure and electronic coupling of photoinduced charge-separated state: 9,10-anthraquinone-1-sulfonate bound to human serum albumin.
abstract: To elucidate how the protein-ligand docking structure affects electronic interactions in the electron-transfer process, we have analyzed time-resolved electron paramagnetic resonance spectra of photoinduced charge-separated (CS) states generated by light excitation of 9,10-anthraquinone-1-sulfonate (AQ1S(-)) bound to human serum albumin at a hydrophobic drug-binding region. The spectra have been explained in terms of the triplet-triplet electron spin polarization transfer model to determine both the geometries and the exchange couplings of the CS states of AQ1S(2-•)-histidine-242 radical cation (H242(+•)) and AQ1S(2-•)-tryptophan-214 radical cation (W214(+•)). For the CS state of the former, it has been revealed that, due to the orthogonal relationship between the singly occupied molecular orbitals of AQ1S(2-•) and H242(+•), the electronic coupling (5.4 cm(-1)) is very weak, contributing to the prevention of energy-wasting charge recombination, even at a contact edge-to-edge separation.
authors.affiliation: Department of Chemistry, Faculty of Science, Shizuoka University, 836 Ohya Suruga-ku, Shizuoka 422-8529, Japan. sykobor@ipc.shizuoka.ac.jp
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Kobori
authors.forename: Masaaki
authors.initials: M
authors.lastname: Fuki
mesh_terms: D000880:Anthraquinones / Q000737:chemistry*; D018360:Crystallography, X-Ray; D004583:Electrons; D006801:Humans; D008024:Ligands; D008027:Light; D015394:Molecular Structure; D012709:Serum Albumin / Q000737:chemistry*; D014859:Warfarin / Q000737:chemistry
chemical_list: D000880:Anthraquinones; D008024:Ligands; D012709:Serum Albumin; C042834:9,10-anthraquinone; D014859:Warfarin; C101046:anthraquinone 1-sulfonate