Excited state interactions between flurbiprofen and tryptophan in drug–protein complexes and in model dyads. Fluorescence studies from the femtosecond to the nanosecond time domains

Abstract

We report here on the interaction dynamics between flurbiprofen (FBP) and tryptophan (Trp) covalently linked in model dyads and in a complex of FBP with human serum albumin (HSA) probed by time-10 resolved fluorescence spectroscopy from the femto-to the nano-second timescales. In the dyads, a rapid (k > 10 10 s -1 ) dynamic quenching of the 1 FBP* fluorescence is followed by a slower (k > 10 9 s -1 ) quenching of the remaining 1 Trp* fluorescence. Both processes display a clear stereoselectivity; the rates are 2-3 times higher for the (R,S)-dyad. In addition, a red-shifted exciplex emission is observed, rising in 100-200 ps. A similar two-step dynamic fluorescence quenching is also observed in the FBP/HSA 15 complex, although the kinetics of the involved processes are slower. The characteristic reorientational times determined for the two enantiomeric forms of FBP in the protein show that the interaction is stronger for the (R)-form. This is, to our knowledge, the first observation of stereo-selective flurbiprofentryptophan interaction dynamics with femtosecond time resolution.

Can Förster Theory Describe Stereoselective Energy Transfer Dynamics in a Protein–Ligand Complex?

“…In line with the absorption spectra of the dyads, 14 In order to get further insights in the origin of the coupling values, in Table 2 Overall, the results found for the dyad strongly support an energy transfer process from the 1FBP* state to the Trp L a state as the origin for the observed dynamic quenching. In addition, they show that capturing the proper orientation for the Trp L a dipole, as well as the proper balance among (S,S)-conformers, is key in order to explain the observed enantioselectivity.…”

“…In particular, ibuprofen is bound to the well-known site II of HSA, but also to a secondary site of HSA located between subdomains IIA and IIB. 50 We align FBP enantiomers in order to place them at this secondary site, as an energy transfer in the subnanosecond timescale is only compatible with that binding mode, populated by 30-40% of FBP enantiomers in the experimental conditions we aim at simulating, 14,46 as will be discussed in the results section. We assumed a standard protonation state for all residues except Glu244, which was in the neutral state, as indicated by pKa estimates at neutral pH computed using the PROPKA3 server.…”

“…In particular, we investigate the enantioselective fluorescence dynamic quenching recently observed by Vayá and co-workers in the complex between human serum albumin (HSA) and the (S)-and (R)enantiomers of flurbiprofen (FBP), which have been ascribed to excitation transfer from 1FBP* to the Trp214 residue in HSA. 14 Characterizing the binding of drugs to HSA is important to understand their pharmacodynamic and pharmacokinetic profile, given that HSA is the major transport plasma protein. 43,44 In this case, we study the binding of flurbiprofen, a chiral nonsteroidal anti-inflammatory drug (NSAID), in which the (S)enantiomer shows most of the anti-inflammatory activity, although both enantiomers posses analgesic activity.…”

Photoinduced Interaction of Atorvastatin with Acetophenone

“…A present-day scientific Electronic supplementary material The online version of this article (doi:10.1007/s00723-014-0632-5) contains supplementary material, which is available to authorized users. trend is the using of modern physical methods to study the biologically relevant processes in which drugs are involved in [2][3][4]. In particular, spin chemistry methods [chemically induced dynamic nuclear polarization (CIDNP) and magnetic effect] have been used to study some of the elementary processes of drug-receptor and drug-enzyme interactions [5][6][7][8].…”

Drug/protein interactions studied by time-resolved fluorescence spectroscopy

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ABSTRACTWe report here on a recent time-resolved fluorescence study [1] of the interaction between flurbiprofen (FBP), a chiral non-steroidal anti-inflammatory drug, and human serum albumin (HSA), the main transport protein in the human body. We compare the results obtained for the drug-protein complex with those of various covalently linked flurbiprofentryptophan dyads having well-defined geometries.

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