Binding of a chiral drug to a protein: an investigation of the 2-(3-benzoylphenyl)propionic acid/bovine serum albumin system by circular dichroism and fluorescence.
A combined approach using global analysis of circular dichroism multiwavelength data and time resolved fluorescence was applied to investigate the interaction of R-(-)- and S-(+)-ketoprofen with bovine serum albumin in buffer solution at neutral pH. A characterization of the most stable drug : protein adducts of 1 : 1 and 2 : 1 stoichiometry, as individual chemical species, was obtained. The stability constants and the absolute circular dichroism spectra of the diastereomeric complexes were determined. The spectra of the 1 : 1 conjugates are opposite in sign, those of the 2 : 1 complexes are both negative, but different in shape from each other (peaks at 358 and 342 nm for S-(+)- and R-(-)-ketoprofen, respectively). A tryptophan residue was shown to be involved in the binding of the drug, in the primary site for the R-(-) and in the secondary site for the S-(+) enantiomer, thereby showing that chiral recognition by the protein causes the site of highest affinity being not the same for both optical antipodes.
Monti
Sandra
S
Istituto per la Sintesi Organica e la Fotoreattività-ISOF, CNR Area della Ricerca, Via P. Gobetti 101, 40129 Bologna, Italy. monti@isof.cnr.it
Manoli
Francesco
F
Sortino
Salvatore
S
Morrone
Raffaele
R
Nicolosi
Giovanni
G
D000818:Animals; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000737:chemistry*; D001665:Binding Sites; D002417:Cattle; D002626:Chemistry, Pharmaceutical / Q000379:methods; D002942:Circular Dichroism / Q000379:methods*; D006863:Hydrogen-Ion Concentration; D007660:Ketoprofen / Q000737:chemistry*; D015233:Models, Statistical; D008968:Molecular Conformation; D011485:Protein Binding; D012710:Serum Albumin, Bovine / Q000737:chemistry*; D013050:Spectrometry, Fluorescence / Q000379:methods*; D013053:Spectrophotometry / Q000379:methods; D013237:Stereoisomerism; D013997:Time Factors
D000894:Anti-Inflammatory Agents, Non-Steroidal; D012710:Serum Albumin, Bovine; D007660:Ketoprofen