Luminescence Amplification by Enzymatic Eu2+ Oxidation to Eu3+ for Time-Resolved Peroxidase Activity Measurement

Abstract

A novel peroxidase activity assay was developed for horseradish peroxidase (HRP) and myeloperoxidase (MPO), in which substrate Eu 2+ was catalytically oxidized to Eu 3+ , and the Eu 3+ luminescence was enhanced by the addition of sensitizer 4,4′-bis(1″,1″,1″,2″,2″,3″,3″-hepatafluoro-4″,6″-hexanedione-6″-yl)chlorosulfo-o-terphenyl (BHHCT) for time-resolved measurement of the BHHCT-Eu 3+ complex. Since BHHCT-Eu 3+ has a long lifetime (more than 500 μs), typical of Eu 3+ oxidation state, and the emission wavelength (615 nm) is totally different from those of Eu 2+ complexes, time-resolved luminescence measurement of the Eu 3+ complex enabled suppressed background and high signal/background ratio. The present method was successfully applied to monitor the oxidative stress level, which is closely associated with peroxidase activity level, in rat heart muscle homogenates. Notable parallel temporal change was observed for peroxidase activity and 4-hydroxynonenal (HNE) concentration after lipopolysaccharide (LPS) injection for induction of oxidative stress in rats. Such a relation does not contradict the oxidative stress mechanism that HNE is produced via lipid peroxidation, which is caused by the • OH radical generated by peroxidase activity.

A EuIII Tetrakis(β-diketonate) Dimeric Complex: Photophysical Properties, Structural Elucidation by Sparkle/AM1 Calculations, and Doping into PMMA Films and Nanowires

“…Among them, the luminescence efficiency follows the order tris < tris-adduct < tetrakis. As an extension of the initial ligands, bis(β-diketonates) have been proposed, either for now well-established bioanalyses or for isolating dinuclear Eu III complexes. The latter are attracting much attention, because of their high thermal stability, excellent photoluminescent and electroluminescent properties, , formation of helical structures, , and visible-light sensitization …”