title: Effect of dye localization and self-interactions on the photosensitized generation of singlet oxygen by rose bengal bound to bovine serum albumin.
abstract: The spectroscopic and photophysical properties of rose bengal (RB) encased in bovine serum albumin (BSA) have been examined to evaluate the photosensitized generation of singlet molecular oxygen ((1)O2). The results show that RB photophysical and photosensitizing properties are highly modulated by the average number of dye molecules per protein (n). At n ≪ 1, the dye molecule is tightly located into the hydrophobic nanocavity site I of the BSA molecule with a binding constant Kb = 0.15 ± 0.01 μM(-1). The interaction with surrounding amino acids induces heterogeneous decay of both singlet and triplet excited states of RB and partially reduce its triplet quantum yield as compared with that in buffer solution. However, despite of the diffusive barrier imposed by the protein nanocavity to (3)O2, the quenching of (3)RB(∗):BSA generates (1)O2 with quantum yield ΦΔ = 0.35 ± 0.05. In turns, the intraprotein generated (1)O2 is able to diffuse through the bulk solution, where is dynamically quenched by BSA itself with an overall quenching rate constant of 7.3 × 10(8) M(-1) s(-1). However, at n>1, nonspecific binding of up to ≈ 6RB molecules per BSA is produced, allowing efficient static quenching of excited states of RB preventing photosensitization of (1)O2. These results provide useful information for development of dye-protein adducts suitable for using as potential intracellular photosensitizers.
authors.affiliation: Laboratorio de Cinética y Fotoquímica, CITSE-CONICET, Universidad Nacional de Santiago del Estero, RN9, km 1125, CP4206 Santiago del Estero, Argentina.
authors.forename: María Beatriz Espeche
authors.initials: MB
authors.lastname: Turbay
authors.affiliation: Laboratorio de Cinética y Fotoquímica, CITSE-CONICET, Universidad Nacional de Santiago del Estero, RN9, km 1125, CP4206 Santiago del Estero, Argentina.
authors.forename: Valentina
authors.initials: V
authors.lastname: Rey
authors.affiliation: Laboratorio de Cinética y Fotoquímica, CITSE-CONICET, Universidad Nacional de Santiago del Estero, RN9, km 1125, CP4206 Santiago del Estero, Argentina.
authors.forename: Natalia M
authors.initials: NM
authors.lastname: Argañaraz
authors.affiliation: Laboratorio de Cinética y Fotoquímica, CITSE-CONICET, Universidad Nacional de Santiago del Estero, RN9, km 1125, CP4206 Santiago del Estero, Argentina.
authors.forename: Faustino E
authors.initials: FE
authors.lastname: Morán Vieyra
authors.affiliation: Departamento de Ciencias del Ambiente, Facultad de Química y Biología, Universidad de Santiago de Chile, USACH, Av. Bernardo O'Higgins, 3363 Santiago, Chile.
authors.forename: Alexis
authors.initials: A
authors.lastname: Aspée
authors.affiliation: Departamento de Ciencias del Ambiente, Facultad de Química y Biología, Universidad de Santiago de Chile, USACH, Av. Bernardo O'Higgins, 3363 Santiago, Chile.
authors.forename: Eduardo A
authors.initials: EA
authors.lastname: Lissi
authors.affiliation: Laboratorio de Cinética y Fotoquímica, CITSE-CONICET, Universidad Nacional de Santiago del Estero, RN9, km 1125, CP4206 Santiago del Estero, Argentina. Electronic address: cdborsarelli@gmail.com.
authors.forename: Claudio D
authors.initials: CD
authors.lastname: Borsarelli
mesh_terms: D000818:Animals; D002417:Cattle; D057927:Hydrophobic and Hydrophilic Interactions; D007700:Kinetics; D017319:Photosensitizing Agents / Q000737:chemistry* / Q000378:metabolism; D011485:Protein Binding; D011789:Quantum Theory; D012395:Rose Bengal / Q000737:chemistry* / Q000378:metabolism; D012710:Serum Albumin, Bovine / Q000737:chemistry* / Q000378:metabolism; D026082:Singlet Oxygen / Q000737:chemistry* / Q000378:metabolism; D013050:Spectrometry, Fluorescence
chemical_list: D017319:Photosensitizing Agents; D026082:Singlet Oxygen; D012395:Rose Bengal; D012710:Serum Albumin, Bovine