Spectroscopic detection of adrenaline-quinone formation in micelles.
Spectral changes, from 200 nm to 600 nm, of the oxidation of adrenaline to adrenochrome induced by periodate in electrically charged and neutral micelles at pH 3.77 were studied. The observed variations of the peak position, intensity and shape of the fluorescence spectra indicated that depending on the charge of the micelle adrenaline ion is partially embedded into the micellar core. Fluorescence lifetime measurements using Omnilyzer allowed to calculate partition coefficients of 0.36, 0.05 and 0.01 in sodium dodecyl sulphate, tetradodecyltrimethylammonium bromide and Triton X-100, respectively. Kinetics of adrenaline decay during oxidation were followed by its fluorescence what overcame spectral interference in the absorption spectra of adrenaline from the formed intermediates. Scanning absorption spectroscopy, with 100 ms resolution, allowed the recording of spectral changes during the transformation. With this method, the formation of adrenaline-quinone with absorption maxima at 388 nm and 274 nm was detected. The calculated rate constants of the observed kinetics during oxidation were significantly lowered in both charged micelles compared to buffer solution and in Triton X-100 neutral micelles. The observed phenomena are discussed in terms of the electrostatic forces mechanism and in the frame of the Raper-Mason scheme of adrenaline transformation.
Polewski
K
K
Agricultural University, Poznań, Poland. polewski@owl.au.poznan.pl
D000323:Adrenochrome / Q000737:chemistry*; D004837:Epinephrine / Q000737:chemistry*; D007700:Kinetics; D008823:Micelles; D010084:Oxidation-Reduction; D011809:Quinones / Q000737:chemistry*; D012997:Solvents; D013050:Spectrometry, Fluorescence / Q000379:methods; D013053:Spectrophotometry / Q000379:methods
D008823:Micelles; D011809:Quinones; D012997:Solvents; D000323:Adrenochrome; D004837:Epinephrine