title: Femtochemistry of orange II in solution and in chemical and biological nanocavities.
abstract: In this work, we report on studies of the nature of the dynamics and hydrophobic binding in cyclodextrins and human serum albumin protein complexes with orange II. With femtosecond time resolution, we examined the proton-transfer and trans-cis isomerization reactions of the ligand in these nanocavities and in pure solvents. Because of confinement at the ground state, the orientational motion in the formed phototautomer is restricted, leading to a rich dynamics. Therefore, the emission lifetimes span a large window of tens to hundreds of picoseconds in the cavities. Possible H-bond interactions between the guest and cyclodextrin do not affect the caged dynamics. For the protein-ligand complexes, slow diffusional motion ( approximately 630 ps) observed in the anisotropy decay indicates that the binding structure is not completely rigid, and the embedded guest is not frozen with the hydrophobic pocket. The ultrafast isomerization and decays are explained in terms of coupling motions between N-N and C-N stretching modes of the formed tautomer. We discuss the role of confinement on the trans-cis isomerization with the cavities and its relationships to frequency and time domains of nanostructure emission.
authors.affiliation: Departamento de Química Física, Sección de Químicas, Facultad de Ciencias del Medio Ambiente, Universidad de Castilla-La Mancha, Avenida Carlos III, S.N., 45071 Toledo, Spain. abderrazzak.douhal@uclm.es
authors.forename: Abderrazzak
authors.initials: A
authors.lastname: Douhal
authors.forename: Mikel
authors.initials: M
authors.lastname: Sanz
authors.forename: Laura
authors.initials: L
authors.lastname: Tormo
mesh_terms: D016880:Anisotropy; D001391:Azo Compounds / Q000737:chemistry* / Q000494:pharmacology; D001557:Benzenesulfonates / Q000737:chemistry* / Q000494:pharmacology; D002244:Carbon / Q000737:chemistry; D004396:Coloring Agents / Q000737:chemistry / Q000494:pharmacology; D003505:Cyclodextrins / Q000737:chemistry; D006860:Hydrogen Bonding; D008024:Ligands; D008027:Light; D050356:Lipid Metabolism; D008956:Models, Chemical; D008958:Models, Molecular; D008968:Molecular Conformation; D015394:Molecular Structure; D009584:Nitrogen / Q000737:chemistry; D004364:Pharmaceutical Preparations / Q000737:chemistry; D010777:Photochemistry; D011522:Protons; D012160:Retina / Q000378:metabolism; D012243:Rhodopsin / Q000737:chemistry; D013053:Spectrophotometry; D013696:Temperature; D013997:Time Factors; D014466:Ultraviolet Rays
chemical_list: D001391:Azo Compounds; D001557:Benzenesulfonates; D004396:Coloring Agents; D003505:Cyclodextrins; D008024:Ligands; D004364:Pharmaceutical Preparations; D011522:Protons; D002244:Carbon; D012243:Rhodopsin; D009584:Nitrogen; C014722:2-naphthol orange