Fluorescence matching

Not only the stationary band maxima of absorption and fluorescence match this formula but also the radical absorption and even the triplet and singlet excited state absorption. Thereby the fitting parameters have been altered. 

Decomposition of diphenoylperoxide [6109-04-2] (40) in the presence of a fluorescer such as perylene in methylene chloride at 24°C produces chemiluminescence matching the fluorescence spectmm of the fluorescer with perylene was reported to be 10 5% (135). The reaction follows pseudo-first-order kinetics with the observed rate constant increasing with fluorescer concentration according to = k [flr]. Thus the fluorescer acts as a catalyst for peroxide decomposition, with catalytic decomposition competing with spontaneous thermal decomposition. An electron-transfer mechanism has been proposed (135). 

The carbonyl compound (43) has also been synthesi2ed, and its fluorescence spectmm has been shown to match the bioluminescence spectmm under equivalent conditions (214). The details of the excitation step are unclear and a dioxetanone mechanism (59,215) may apply to the reaction. 

Liquid scintillation counting is by far the most common method of detection and quantitation of -emission (12). This technique involves the conversion of the emitted P-radiation into light by a solution of a mixture of fluorescent materials or fluors, called the Hquid scintillation cocktail. The sensitive detection of this light is affected by a pair of matched photomultiplier tubes (see Photodetectors) in the dark chamber. This signal is amplified, measured, and recorded by the Hquid scintillation counter. Efficiencies of detection are typically 25—60% for tritium >90% for and P and... 

Wavelength dispersive x-ray fluorescence spectrometric (xrf) methods using the titanium line at 0.2570 nm may be employed for the determination of significant levels of titanium only by carefiil matrix-matching. However, xrf methods can also be used for semiquantitative determination of titanium in a variety of products, eg, plastics. Xrf is also widely used for the determination of minor components, such as those present in the surface coating, in titanium dioxide pigments. 

Color-order systems, such as the many MunseU collections available from Macbeth, have been described previously. Essential for visual color matching is a color-matching booth. A typical one, such as the Macbeth Spectrahte, may have available a filtered 7500 K incandescent source equivalent to north-sky daylight, 2300 K incandescent illumination as horizon sunlight, a cool-white fluorescent lamp at 4150 K, and an ultraviolet lamp. By using the various illuminants, singly or in combination, the effects of metamerism and fluorescence can readily be demonstrated and measured. Every user should be checked for color vision deficiencies. 

NAA is a quantitative method. Quantification can be performed by comparison to standards or by computation from basic principles (parametric analysis). A certified reference material specifically for trace impurities in silicon is not currently available. Since neutron and y rays are penetrating radiations (free from absorption problems, such as those found in X-ray fluorescence), matrix matching between the sample and the comparator standard is not critical. Biological trace impurities standards (e.g., the National Institute of Standards and Technology Standard Rference Material, SRM 1572 Citrus Leaves) can be used as reference materials. For the parametric analysis many instrumental fiictors, such as the neutron flux density and the efficiency of the detector, must be well known. The activation equation can be used to determine concentrations ... 

Fig. 7.1.5 Fluorescence spectra of purified Chaetopterus photoprotein (CPA) in 10 mM ammonium acetate, pH 6.7 (solid lines), and the bioluminescence spectrum of the luminous slime of Chaetopterus in 10 mM Tris-HCl, pH 7.2 (dashed line). Note that the luminescence spectrum of Chaetopterus photoprotein in 2 ml of 10 mM Tris-HCl, pH 7.2, containing 0.5 M NaCl, 5 pi of old dioxane and 2 pi of 10 mM FeSC>4 (Amax 453-455 nm) matched exactly with the fluorescence emission spectrum of the photoprotein. No significant change was observed in the fluorescence spectrum after the luminescence reaction.

Oxyluciferin. During the luminescence reaction catalyzed by luciferase, luciferin is converted into a fluorescent compound, oxyluciferin, accompanied by the emission of greenish-blue light that spectrally matches the fluorescence of oxyluciferin (Fig. 7.2.6). The absorption spectrum of oxyluciferin is shown in Figs. 7.2.1 and 7.2.2. 

Fig. 3.19 Sequence-specific fluorescence detection of DNA. (Top) Model of polyamide-TMR conjugate bound to DNA. In aqueous solutions, the hairpin polyamide-fluorophore displays fluorescence enhancement only upon binding to its match DNA site. Black and white spheres represent imidazole and pyrrole...

NPQ (Rakhimberdieva et al. 2004) exactly matches the absorption spectrum of the carotenoid, 3 -hydrox yech i nenone (Polivka et al. 2005) in the OCP. The OCP is now known to be specifically involved in the phycobilisome-associated NPQ and not in other mechanisms affecting the levels of fluorescence such as state transitions or D1 damage (Wilson et al. 2006). Studies by immunogold labeling and electron microscopy showed that most of the OCP is present in the interthylakoid cytoplasmic region, on the phycobilisome side of the membrane, Figure 1.2 (Wilson et al. 2006). The existence of an interaction between the OCP and the phycobilisomes and thylakoids was supported by the co-isolation of the OCP with the phycobilisome-associated membrane fraction (Wilson et al. 2006, 2007). 

Fig. 42. The unfolded baseline and the Cyt c burst phase. The solid curves show the equilibrium behavior of Cyt c. The equilibrium fluorescence and CD of the (unfolded) fragments (A and <>) match the unfolded holo Cyt c baseline at high GdmCl and define the continuation of the unfolded baseline to lower GdmCl concentrations. The horizontal dashed line shows the initial fluorescence and CD in the stopped-flow experiments (4.3 M GdmCl). The solid symbols indicate the fluorescence (A) and the ellipticity at 222 nm (B) reached by holo Cyt c in the burst phase on dilution into lower (or higher) GdmCl, as suggested by the arrows (starting from either pH 2 ( ) or pH 4.9 ( )). These comparisons are made on an absolute, per-molecule basis. Forster-averaged distance (Trp-59 to heme) is at the right of A. (From Sosnick et al., 1997, with permission. 1997, National Academy of Sciences, USA.)...

The basic layout of Raman sensors is similar to fluorescence probes. The common sensor form is that of a fibre optic probe, with excitation and collection fibres. As the excitation light comes from a monochromatic source no excitation filter is required, but a spectrally matched emission notch filter blocking the excitation wavelength is almost always part of the sensor head. 

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