Emissions fluorescent

The most widely employed optical method for the study of chemical reaction dynamics has been laser-induced fluorescence. This detection scheme is schematically illustrated in the left-hand side of figure B2.3.8. A tunable laser is scanned tlnough an electronic band system of the molecule, while the fluorescence emission is detected. This maps out an action spectrum that can be used to detemiine the relative concentrations of the various vibration-rotation levels of the molecule. 

Chloride ion is known to quench the intensity of quinine s fluorescent emission. For example, the presence of 100 ppm NaCI (61 ppm Ch) gives an emission intensity that is only 83% of that without chloride, whereas the presence of 1000 ppm NaCI (610 ppm Ch) gives a fluorescent emission that is only 29% as intense. The concentration of chloride in urine typically ranges from 4600 to 6700 ppm Ch. Flow is an interference from chloride avoided in this procedure ... 

The fluorescent emission for quinine at 450 nm can be induced using an excitation frequency of either 250 nm or 350 nm. The fluorescent quantum efficiency is known to be the same for either excitation wavelength, and the UV absorption spectrum shows that 250 is greater than 350- Nevertheless, fluorescent emission intensity is greater when using 350 nm as the excitation wavelength. Speculate on why this is the case. 

A 0.5113-g sample of dry dog food was ashed to remove organic materials, and the residue dissolved in a small amount of HCl and diluted to volume in a 50-mL volumetric flask. Analysis of the resulting solution gave a fluorescent emission intensity of 5.72. Determine the parts per million of Fe in the sample of dog food. 

Fluorescence from the ExcitedSj State. In Figure 1, after absorption (A) and vibrational deactivation (VD) occur, the lowest or nearly lowest level of the singlet excited state is reached. If the molecule is fluorescent with a high quantum efficiency, fluorescent emission of a quantum of... 

Fig. 5 Schematic representation of the electronic transitions during luminescence phenomena [5]. — A absorbed energy, F fluorescence emission, P phosphorescence, S ground state. S excited singlet state, T forbidden triplet transition.

Fig. 27 Schematic representation of the relationship between absorption and fluorescence emission of the molecules — m and m are the terms involved in the vibrational quantum numbers [4],...

Figure 49 shows that porphynns are decomposed in the layer within a few hours if no special measures are taken, but that they can be stabilized for more than 24 hours if the layers are dipped m 50% paraffin solution and stored in the dark. This was true of all six porphynns investigated (Fig. 52). Quantitation should not be undertaken less than an hour after dipping the chromatograms, because it takes so long for the fluorescence emission to stabilize [230].

The conformation of bovine myelin basic protein (MBP) in AOT/isooctane/water reversed micellar systems was studied by Waks et al. 67). This MBP is an extrinsic water soluble protein which attains an extended conformation in aqueous solution 68 but is more density packed at the membrane surface. The solubilization of MBP in the AOT reversed micelles depends on the water/AOT-ratio w0 68). The maximum of solubilization was observed at a w0-value as low as 5.56. The same value was obtained for another major protein component of myelin, the Folch-Pi proteolipid 69). According to fluorescence emission spectra of MBP, accessibility of the single tryptophane residue seems to be decreased in AOT reversed micelles. From CD-spectra one can conclude that there is a higher conformational rigidity in reversed micelles and a more ordered aqueous environment. 

Fig. 1.5 Fluorescence emission spectrum of the luciferase-oxyluciferin complex in the same solution as in Fig. 1.4 (solid line), compared with the luminescence spectrum of firefly luciferin measured in glycylglycine buffer, pH 7.6 (dotted line). The former curve from Gates and DeLuca, 1975 the latter from Selinger and McElroy, 1960, both with permission from Elsevier.

Fig. 2.4 The spectrum of bacterial luminescence measured with B. harveyi luciferase, FMN, tetradecanal and NADH, in 50 mM phosphate buffer, pH 7.0, at 0°C (dashed line from Matheson et al., 1981) and the absorption and fluorescence emission spectra of LumP (solid lines) and Rf-LumP (dotted lines) obtained from P. leiog-natbi, in 25 mM phosphate buffer, pH 7.0, containing 1 mM EDTA and 10 mM 2-mercaptoethanol, at room temperature (from Petushkov et al, 2000, with permission from Elsevier). LumP is a lumazine protein, and Rf-LumP contains riboflavin instead of lumazine in the lumazine protein. Fluorescence emission curves are at the right side of the absorption curves.

Fig. 3.1.4 Bioluminescence spectrum of Cypridina luciferin catalyzed by Cypridina luciferase (A), the fluorescence excitation spectrum of oxyluciferin in the presence of luciferase (B), the fluorescence emission spectrum of the same solution as B (C), and the absorption spectrum of oxyluciferin (D). The fluorescence of oxyluciferin alone and luciferase alone are negligibly weak. Measurement conditions A, luciferin (lpg/ml) plus a trace amount of luciferase in 20 mM sodium phosphate buffer, pH 7.2, containing 0.2 M NaCl B and C, oxyluciferin (20 pM) plus luciferase (0.2mg/ml) in 20 mM sodium phosphate buffer, pH 7.2, containing 0.2 M NaCl D, oxyluciferin (41 pM) in 20 mM Tris-HCl buffer, pH 7.6, containing 0.2 M NaCl. All are at 20°C.

Fig. 4.1.3 Absorption spectra of aequorin (A), spent solution of aequorin after Ca2+-triggered luminescence (B), and the chromophore of aequorin (C). Fluorescence emission spectrum of the spent solution of aequorin after Ca2+-triggered bioluminescence, excited at 340 nm (D). Luminescence spectrum of aequorin triggered with Ca2+ (E). Curve C is a differential spectrum between aequorin and the protein residue (Shimomura et al., 1974b) protein concentration 0.5 mg/ml for A and B, 1.0 mg/ml for C. From Shimomura and Johnson, 1976.

Fig. 4.1.15 Comparison of the luminescence and fluorescence emission spectra of natural aequorin (left panel) and recombinant e-aequorin (right panel) the luminescence spectra of Ca2+ -triggered reaction (dark solid lines), the fluorescence emission spectra of the spent solution containing 2 mM Ca2+ (dashed lines), and the luminescence spectra of the spent solution after addition of coelenterazine (light solid lines). Reproduced with permission, from Shimomura, 1995d. the Biochemical Society.

Fig. 4.2.1 Luminescence spectra of the Ca2+-triggered light emission of recombinant obelins (dotted lines), and the fluorescence emission spectra of their spent solution after luminescence (solid lines). Left obelin derived from O. geniculata right obelin derived from O. longissima. Reproduced from Markova etal., 2002, with permission from the American Chemical Society.

Fig. 4.2.2 Left panel-. Uncorrected Ca2+-triggered bioluminescence spectrum of W92F obelin derived from O. longissima. Right panel Corrected bioluminescence spectrum of the same obelin (dotted line), and the fluorescence emission spectrum of the spent solution after luminescence (solid line). From Deng et al., 2001, with permission of the Federation of the European Biochemical Societies.

Fluorescence emission maximum Fluorescence quantum yield Molar absorption coefficient (e) at peak wavelengths (as monomer)... 

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