Room temperature fluorescence and phosphorescence study on the interactions of iodide ions with single tryptophan containing serum albumins.
In this study, the influence of heavy-atom perturbation, induced by the addition of iodide ions, on the fluorescence and phosphorescence decay parameters of some single tryptophan containing serum albumins isolated from: human (HSA), equine (ESA) and leporine (LSA) has been studied. The obtained results indicated that, there exist two distinct conformations of the proteins with different exposure to the quencher. In addition, the Stern-Volmer plots indicated saturation of iodide ions in the binding region. Therefore, to determine quenching parameter, we proposed alternative quenching model and we have performed a global analysis of each conformer to define the effect of iodide ions in the cavity by determining the value of the association constant. The possible quenching mechanism may be based on long-range through-space interactions between the buried chromophore and quencher in the aqueous phase. The discrepancies of the decay parameters between the albumins studied may be related with the accumulation of positive charge at the main and the back entrance to the Drug Site 1 where tryptophan residue is located.
Institute of General Food Chemistry, Faculty of Biotechnology and Food Sciences, Technical University of Lodz, ul. Stefanowskiego 4/10, 90-924 Lodz, Poland. Electronic address: krystian.galecki@p.lodz.pl.
Krystian
K
Gałęcki
Institute of General Food Chemistry, Faculty of Biotechnology and Food Sciences, Technical University of Lodz, ul. Stefanowskiego 4/10, 90-924 Lodz, Poland.
Agnieszka
A
Kowalska-Baron
D000818:Animals; D005453:Fluorescence; D006736:Horses; D006801:Humans; D007454:Iodides / Q000737:chemistry / Q000378:metabolism*; D008163:Luminescent Measurements; D008958:Models, Molecular; D011485:Protein Binding; D011487:Protein Conformation / Q000187:drug effects; D011817:Rabbits; D012709:Serum Albumin / Q000737:chemistry / Q000378:metabolism*; D013050:Spectrometry, Fluorescence; D013696:Temperature; D014364:Tryptophan / Q000737:chemistry / Q000378:metabolism*
D007454:Iodides; D012709:Serum Albumin; D014364:Tryptophan
Heavy atom effect; Iodide quenching; Phosphorescence lifetime; Saturation Stern–Volmer plot; Serum albumins