Stereoselective binding of flurbiprofen enantiomers and their methyl esters to human serum albumin studied by time-resolved phosphorescence.
The interaction of the nonsteroidal anti-inflammatory drug flurbiprofen (FBP) with human serum albumin (HSA) hardly influences the fluorescence of the protein's single tryptophan (Trp). Therefore, in addition to fluorescence, heavy atom-induced room-temperature phosphorescence is used to study the stereoselective binding of FBP enantiomers and their methyl esters to HSA. Maximal HSA phosphorescence intensities were obtained at a KI concentration of 0.2 M. The quenching of the Trp phosphorescence by FBP is mainly dynamic and based on Dexter energy transfer. The Stern-Volmer plots based on the phosphorescence lifetimes indicate that (R)-FBP causes a stronger Trp quenching than (S)-FBP. For the methyl esters of FBP, the opposite is observed: (S)-(FBPMe) quenches more than (R)-FBPMe. The Stern-Volmer plots of (R)-FBP and (R)-FBPMe are similar although their high-affinity binding sites are different. The methylation of (S)-FBP causes a large change in its effect on the HSA phosphorescence lifetime. Furthermore, the quenching constants of 3.0 × 10(7) M(-1) s(-1) of the R-enantiomers and 2.5 × 10(7) M(-1) s(-1) for the S-enantiomers are not influenced by the methylation and indicate a stereoselectivity in the accessibility of the HSA Trp to these drugs.
Department of Biomolecular Analysis and Spectroscopy, LaserLaB, VU University Amsterdam, The Netherlands.
Ivonne
I
Lammers
Virginie
V
Lhiaubet-Vallet
M
M
Consuelo Jiménez
Freek
F
Ariese
Miguel A
MA
Miranda
Cees
C
Gooijer
D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000737:chemistry* / Q000378:metabolism; D004952:Esters / Q000737:chemistry*; D005480:Flurbiprofen / Q000737:chemistry* / Q000378:metabolism; D006801:Humans; D008163:Luminescent Measurements; D011485:Protein Binding; D012709:Serum Albumin / Q000737:chemistry* / Q000378:metabolism; D013237:Stereoisomerism; D013997:Time Factors
D000894:Anti-Inflammatory Agents, Non-Steroidal; D004952:Esters; D012709:Serum Albumin; D005480:Flurbiprofen