title: Chemical and biological caging effects on the relaxation of a proton-transfer dye.
abstract: We report studies of the interaction between a proton-transfer dye (1'-hydroxy,2'-acetonaphthone, HAN), with the human serum albumin (HSA) protein and a beta-cyclodextrin derivative (DM-beta-CD) in neutral water solutions. We used steady-state and picosecond time-resolved emission spectroscopy to follow the structural changes of HAN due to the hydrophobicity and confinement effect of these nanocavities. Upon encapsulation, the fluorescence intensity of the 1:1 inclusion complex in both cavities increases, and the emission lifetimes become longer. For the DM-beta-CD complexes, we obtained 430 and 920 ps, whereas for the HSA complexes we obtained 630 ps and 2 ns. Picosecond anisotropy measurements show strong confinement due to protein docking. The rotational time for the CD complex is 660 ps, whereas for the protein complex we find 6 ns. The process of energy transfer from the excited triptophan 214 (Trp214) of HSA to the trapped HAN occurs with high efficiency (71%), and the calculated distance between both chromophores is 17 A. We believe that the results are important for a better understanding of the processes occurring in inclusion complexes such as those in nanopharmacodynamics.
authors.affiliation: Departamento de Química Física, Sección de Químicas, Facultad del Medio Ambiente, Universidad de Castilla La Mancha, Avenida Carlos III, S.N., Campus Tecnológico de Toledo, Toledo, Spain.
authors.forename: Juan Angel
authors.initials: JA
authors.lastname: Organero
authors.forename: Cristina
authors.initials: C
authors.lastname: Martin
authors.forename: Boiko
authors.initials: B
authors.lastname: Cohen
authors.forename: Abderrazzak
authors.initials: A
authors.lastname: Douhal
mesh_terms: D016880:Anisotropy; D002627:Chemistry, Physical / Q000379:methods; D004396:Coloring Agents / Q000737:chemistry*; D004735:Energy Transfer; D006801:Humans; D015233:Models, Statistical; D008968:Molecular Conformation; D010777:Photochemistry / Q000379:methods; D011522:Protons; D012709:Serum Albumin / Q000737:chemistry*; D013050:Spectrometry, Fluorescence / Q000379:methods; D013053:Spectrophotometry / Q000379:methods; D013696:Temperature; D014867:Water / Q000737:chemistry; D047392:beta-Cyclodextrins / Q000737:chemistry
chemical_list: D004396:Coloring Agents; D011522:Protons; D012709:Serum Albumin; D047392:beta-Cyclodextrins; D014867:Water; C031215:betadex