Chemical and biological caging effects on the relaxation of a proton-transfer dye.
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.
Organero
Juan Angel
JA
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.
Martin
Cristina
C
Cohen
Boiko
B
Douhal
Abderrazzak
A
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
D004396:Coloring Agents; D011522:Protons; D012709:Serum Albumin; D047392:beta-Cyclodextrins; D014867:Water; C031215:betadex