title: Evaluation by fluorescence, STD-NMR, docking and semi-empirical calculations of the o-NBA photo-acid interaction with BSA.
abstract: Serum albumins present reversible pH dependent conformational transitions. A sudden laser induced pH-jump is a methodology that can provide new insights on localized protein (un)folding processes that occur within the nanosecond to microsecond time scale. To generate the fast pH jump needed to fast-trigger a protein conformational event, a photo-triggered acid generator as o-nitrobenzaldehyde (o-NBA) can be conveniently used. In order to detect potential specific or nonspecific interactions between o-NBA and BSA, we have performed ligand-binding studies using fluorescence spectroscopy, saturation transfer difference (STD) NMR, molecular docking and semi-empirical calculations. Fluorescence quenching indicates the formation of a non-fluorescent complex in the ground-state between the fluorophore and the quencher, but o-NBA does not bind much effectively to the protein (Ka~4.34×10(3)M(-1)) and thus can be considered a relatively weak binder. The corresponding thermodynamic parameters: ΔG°, ΔS° and ΔH° showed that the binding process is spontaneous and entropy driven. Results of (1)H STD-NMR confirm that the photo-acid and BSA interact, and the relative intensities of the signals in the STD spectra show that all o-NBA protons are equally involved in the binding process, which should correspond to a nonspecific interaction. Molecular docking and semi-empirical calculations suggest that the o-NBA binds preferentially to the Trp-212-containing site of BSA (FA7), interacting via hydrogen bonds with Arg-217 and Tyr-149 residues.
authors.affiliation: Departament of Chemistry, Universidade Federal Rural do Rio de Janeiro, BR 465, km 47, 23890-000 Seropédica, RJ, Brazil; CQC, Chemistry Department, University of Coimbra, 3004-535 Coimbra, Portugal.
authors.forename: Otávio A
authors.initials: OA
authors.lastname: Chaves
authors.affiliation: CQC, Chemistry Department, University of Coimbra, 3004-535 Coimbra, Portugal; Center for Neuroscience and Cell Biology, University of Coimbra, 3004-535 Coimbra, Portugal.
authors.forename: Catarina S H
authors.initials: CS
authors.lastname: Jesus
authors.affiliation: CQC, Chemistry Department, University of Coimbra, 3004-535 Coimbra, Portugal.
authors.forename: Pedro F
authors.initials: PF
authors.lastname: Cruz
authors.affiliation: Departament of Chemistry, Universidade Federal Rural do Rio de Janeiro, BR 465, km 47, 23890-000 Seropédica, RJ, Brazil.
authors.forename: Carlos M R
authors.initials: CM
authors.lastname: Sant'Anna
authors.affiliation: Departament of Chemistry, Universidade Federal Rural do Rio de Janeiro, BR 465, km 47, 23890-000 Seropédica, RJ, Brazil; CQC, Chemistry Department, University of Coimbra, 3004-535 Coimbra, Portugal.
authors.forename: Rui M M
authors.initials: RM
authors.lastname: Brito
authors.affiliation: CQC, Chemistry Department, University of Coimbra, 3004-535 Coimbra, Portugal. Electronic address: serpasoa@ci.uc.pt.
authors.forename: Carlos
authors.initials: C
authors.lastname: Serpa
mesh_terms: D000818:Animals; D001547:Benzaldehydes / Q000737:chemistry / Q000378:metabolism*; D001665:Binding Sites; D002417:Cattle; D019277:Entropy; D006860:Hydrogen Bonding; D062105:Molecular Docking Simulation; D019906:Nuclear Magnetic Resonance, Biomolecular; D011485:Protein Binding; D012710:Serum Albumin, Bovine / Q000737:chemistry / Q000378:metabolism*; D013050:Spectrometry, Fluorescence
chemical_list: D001547:Benzaldehydes; D012710:Serum Albumin, Bovine; C043850:2-nitrobenzaldehyde
keywords: Bovine serum albumin; Fluorescence; Molecular docking; STD-NMR; o-NBA; pH-jump