Time-resolved detection luminescence

H. Harma, T. Soukka, S.Lonnberg, J. Paukkunen, P. Tarkkinen, and T. Lovgren, Zeptomole detection sensitivity of prostate-specific antigen in a rapid microtitre plate assay using time-resolved fluorescence. Luminescence 15, 351-355 (2000). 

Pulse radiolysis, using as time-resolved detection methods optical absorption, luminescence, electrical conductivity or electron spin resonance can be expected to give information on the formation of transient or permanent radiation products and on their movement. 

Another possible solution that has been under development for three decades is to use a pulsed laser and time-resolved detection to allow the Raman photons to be discriminated from the broad luminescence background. The Raman interaction time is virtually instantaneous (less than 1 picosecond), whereas luminescence emission is statistically relatively slow, with minimum hundreds of picoseconds elapsing between electronic excitation and radiative decay. If we illuminate a sample with a very short (= 1 ps) laser pulse, all of the Raman... 

Gruber, H. J. Kada, G. Pragl, B. Riener, C. Hahn, C. D. Harms, G. S. Ahrer, W. Dax, T. G. Hohenthanner, K. Knaus, H. G. Preparation of thiol-reactive Cy5 derivatives from commercial Cy5 succinimidyl ester. Bioconjug. Chem. 11(2), 161-166. Gudgin Dickinson, E. F. Poliak, A. Diamandis, E. P. Time-resolved detection of lanthanide luminescence for ultrasensitive bioanalytical assays. J. Photochem. Photobiol. B Biol. 1995,27, 3-19. 

Dickson, E.F.G., Poliak, A., and Diamandis, E.P. (1995) Time-resolved detection of lanthanide luminescence ultrasensitive bioanalytical assays for ultrasensitive bioanalytical assays. Journal of Photochemistry and Photobiology B Biology, 27, 3-19. 

Spectrofluorometers with continuous unmodulated excitation can be used to study the spectral properties of lanthanide emission as of any label, but time-resolving capabdities are required for sensitive detection and for studying the temporal properties of luminescence emission. Often time-resolved spectrofluorometers have pulsed excitation and advanced time-resolved detection system capable of resolving under nanosecond luminescence decay times. These have usually complex design and are optimized for flexibility making them expensive and clumsy for routine use. 

In the mechanism of an interfacial catalysis, the structure and reactivity of the interfacial complex is very important, as well as those of the ligand itself. Recently, a powerful technique to measure the dynamic property of the interfacial complex was developed time resolved total reflection fluorometry. This technique was applied for the detection of the interfacial complex of Eu(lII), which was formed at the evanescent region of the interface when bathophenanthroline sulfate (bps) was added to the Eu(lII) with 2-thenoyl-trifuluoroacetone (Htta) extraction system [11]. The experimental observation of the double component luminescence decay profile showed the presence of dinuclear complex at the interface as illustrated in Scheme 5. The lifetime (31 /as) of the dinuclear complex was much shorter than the lifetime (98 /as) for an aqua-Eu(III) ion which has nine co-ordinating water molecules, because of a charge transfer deactivation. 

Different lanthanide metals also produce different emission spectrums and different intensities of luminescence at their emission maximums. Therefore, the relative sensitivity of time-resolved fluorescence also is dependent on the particular lanthanide element complexed in the chelate. The most popular metals along with the order of brightness for lanthanide chelate fluorescence are europium(III) > terbium(III) > samarium(III) > dysprosium(III). For instance, Huhtinen et al. (2005) found that lanthanide chelate nanoparticles used in the detection of human prostate antigen produced relative signals for detection using europium, terbium, samarium, and dysprosium of approximately 1.0 0.67 0.16 0.01, respectively. The emission... 

Lanthanide chelates also can be used in FRET applications with other fluorescent probes and labels (Figure 9.51). In this application, the time-resolved (TR) nature of lanthanide luminescent measurements can be combined with the ability to tune the emission characteristics through energy transfer to an organic fluor (Comley, 2006). TR-FRET, as it is called, is a powerful method to develop rapid assays with low background fluorescence and high sensitivity, which can equal the detection capability of enzyme assays (Selvin, 2000). 

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