Luminescence principles

Since the pioneering work of Kleymann et al. (2002), Betz et al. (2002), Baumeister et al. (2007), and Crute et al. (2002), who showed that compounds identified as inhibitors of the helicase-primase enzyme complex could alleviate herpesvirus-induced disease in animal models, the attention of researchers developing antiviral compounds has been drawn more and more towards the virus-encoded helicases, particularly those of Herpes viruses and of RNA viruses such as Hepatitis C Virus (HCV) and SAKS coronavirus (SARS-CoV). Enzyme activity is usually assayed by measuring NTPase activity in the presence of an appropriate nucleic acid co-substrate although, more recently, novel fiuorimetric and luminescence principles have been applied to the measurement of strand unwinding and/or translocation of the protein along the nucleic acid (Frick 2003, 2006). 

Detection with optodes can be also based on luminescence principles, including emitting or quenching fluorescence of phosphorescence, chemiluminescence, or bioluminescence of conjugates of antibodies or antigens with enzymes. In fluorescent optodes with indicator, the excitation light is introduced into the proximal end of the fiber and travels to the end where it excites immobilized fluorescent indicator. Then some of the isotropically-emitted fluorescence is recaptured by the fiber to a detection system. Many biological molecules show an inherent fluorescence, but... 

The utility and importance of multi-layer device structures was demonstrated in the first report of oiganic molecular LEDs [7]. Since then, their use has been widespread in both organic molecular and polymer LEDs [45, 46], The details of the operating principles of many multi-layer structures continue to be investigated [47—49], The relative importance of charge carrier blocking versus improved carrier transport of the additional, non-luminescent layers is often unclear. The dramatic improvements in diode performance and, in many cases, device lifetime make a detailed understanding of multi-layer device physics essential. 

Before reviewing recent advances in the field of luminescent dendrimers, it is worthwhile recaUing a few elemental principles of electronic spectroscopy. Interested readers are referred to several books and reviews for detailed discussions [2,11,12]. 

Prospecting Lighting Applications with Ligand Field Tools and Density Functional Theory A First-Principles Account of the 4f7-4f65d1 Luminescence of CsMgBr3 Eu2+... 

Principles and Characteristics The term luminescence describes the radiative evolution of energy other than blackbody radiation which may accompany the decay of a population of electronically excited chro-mophores as it relaxes to that of the thermally equilibrated ground state of the system. The frequency of the... 

Fig. 21. Top The general Jablonski diagram for the flavin chromophore. The given wavelengths for absorption and luminescence represent crude average values derived from the actual spectra shown below. Due to the Franck-Condon principle the maxima of the peak positions generally do not represent so-called 0 — 0 transitions, but transitions between vibrational sublevels of the different electronically excited states (drawn schematically). Bottom Synopsis of spectra representing the different electronic transitions of the flavin nucleus. Differently substituted flavins show slightly modified spectra. Absorption (So- - S2, 345 nm S0 -> Si,450nm 1561) fluorescence (Sj — S0) 530 nm 156)) phosphorescence (Ty Sq, 605 nm 1051) triplet absorption (Tj ->Tn,...

Figure 2. Principles of reversible luminescence sensing using photochemical quenching processes (electron, energy or proton transfer). Dye = luminescent indicator Q = quencher species dotted arrow non-radiative deactivation processes. The luminescence intensity (and excited state lifetime) of the indicator dye decreases in the presence of the quencher. The indicator dye is typically supported onto a polymer material in contact with the sample. The quencher may he the analyte itself or a third partner species that interacts with the analyte (see text).

Principle Plant enriched in secretory structures with biologically active secondary metabolites have fluorescing products in the cells and a location of the compounds could be observed using luminescent technique. 

Principle The measurements of fluorescence spectra or /and fluorescence intensity by microspectrofluorimeters, which are a luminescent microscope combined with a multiplayer and a recorder (or a computer). 

Principle A confocal microscopy as a modification of luminescent microscope may produce images of high quality from fluorescing cells and permits the study of cells structures (see Chapter 8). 

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