title: 1D radical motion in protein pocket: proton-coupled electron transfer in human serum albumin.
abstract: Photoinduced, proton-coupled electron transfer (ET) between 9,10-anthraquinone-2,6-disulfonate (ADQS) and an amino acid residue of tryptophan in human serum albumin (HSA) was observed using time-resolved electron paramagnetic resonance (TREPR). The ET reaction reduces the protein binding affinity of the ligand. TREPR chemically induced dynamic electron polarization (CIDEP) spectra establish that photoinduced ET takes place from the tryptophan residue (W214) to the excited triplet state of AQDS2- while bound in subdomain IIA, a protein cleft of HSA. The TREPR CIDEP signals also reveal that the anion radical of the ligand escapes toward the bulk water region by a one-dimensional translation diffusion process within the protein's pocket area. This pilot study of HSA demonstrates how TREPR CIDEP can provide significant means to investigate dynamic characteristics of protein-surface reactions.
authors.affiliation: Department of Chemistry, The University of Chicago, 5735 South Ellis Avenue Chicago, IL 60637, USA. ykobori@uchicago.edu.
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Kobori
authors.forename: James R
authors.initials: JR
authors.lastname: Norris
mesh_terms: D000880:Anthraquinones / Q000737:chemistry*; D003198:Computer Simulation; D004578:Electron Spin Resonance Spectroscopy / Q000379:methods*; D004583:Electrons; D006801:Humans; D057927:Hydrophobic and Hydrophilic Interactions; D008956:Models, Chemical; D008958:Models, Molecular; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D012709:Serum Albumin / Q000737:chemistry* / Q000378:metabolism; D013499:Surface Properties; D014364:Tryptophan / Q000737:chemistry; D014859:Warfarin / Q000737:chemistry
chemical_list: D000880:Anthraquinones; D012709:Serum Albumin; C408124:anthraquinone-2,6-disulfonate; D014859:Warfarin; D014364:Tryptophan