A fluorescence spectrum

Figure 8. Optical spectroscopy of a indocyanine green dye solution (10 5 M in water) (a) fluorescence spectrum obtained by excitation around 780 nm (b) excitation spectrum obtained on top of a microresonator the rectangle in the inset shows the area from which the fluorescence signal is collected.

In order to minimize the effects of possible inaccuracy of the correction factors for the emission spectrum, the standard is preferably chosen to be excitable at the same wavelength as the compound, and with a fluorescence spectrum covering a similar wavelength range. 

A fluorescence spectrum may result from overlapping spectra of several fluorescent species (or several forms of a fluorescent species). If each of them is characterized by a single lifetime, it is possible to decompose the overall spectrum into its components. 

The bisanthraceno-crown ether E-l (Figure 10.26) exhibits a fluorescence spectrum composed of the characteristic monomer and excimer bands. Gradual addition of sodium perchlorate to a solution in methanol induces a decrease in the monomer band and an increase in the excimer band. Complexation is indeed expected to bring closer together the two anthracene units, which favors excimer formation. A 2 1 (metabligand) complex is formed with Na+ in methanol and acetonitrile with a positive cooperative effect (see Appendix B). Interestingly, the overall stability constant obtained from absorption data was found to be lower than that... 

The excited molecules normally release their energy by spontaneous emission of fluorescence, terminating not only in the initial ground state but on all vibronic levels of lower electronic states to which transitions are allowed. This causes a fluorescence spectrum which consists, for instance, in the case of an excited singlet state in a diatomic molecule, of a progression of either single lines (A/ = 0 named Q-lines) or of doublets (A7 = 1 P- and i -lines) ... 

Fig. 7 Fluorescence spectra of a 5-PAA/PE graft (a) after treatment with 10 (filled squares), (b) after washing with THF in a Soxhlet apparatus for 24 h (open squares)-, (c) after treatment with NaOH (open circles). For comparison purposes, a fluorescence spectrum for an oxidized polyethylene Aim without any hyperbranched graft (but with - CO2H groups) that was also treated with 10 is also shown (filled circles)...

Chloroform extraction of the whole products of dry hydrogenation (400 C 60 min 5% Mo 7 MPa H,) of PSOC-1266 produced a strongly fluorescent extract and non-fIncrescent residue. After drying, the extract was seen under the microscope to contain two components with distinctive fluorescence characteristics (Fig. 7). Component 1 had a fluorescence spectrum very similar to that of the oil (hexane-soluble) fraction of the same... 

Figure 12.6—The diverse components of a fluorescence spectrum. The position of the Raman scattering band depends on the wavelength of excitation and the nature of the solvent.

A fluorescence spectrum of arsenic vapour, after exposure to a mercury lamp at a high temperature has been observed (see p. 39).2... 

Figure 5 shows a fluorescence spectrum of perylene (Pe) in a single tri-n-butyl phosphate (TBP) droplet (r = 1.5 fxm) dispersed in water. Although the spectral band shape shorter than 450 nm is somewhat distorted owing to a change in transmittance of the beam splitter of the microscope (Figure 3)... 

The distance between peaks in a fluorescence spectrum is a measure of the energy differences between vibrational levels in the ground state likewise, the peaks in the lowest-energy band of the absorption spectrum give the energy differences between vibrational levels in Sv If the spacings are similar, the absorption and emission spectra are mirror images of one another. 

Fig. 2.12. (a) Fluorescence spectrum of sennoside A on a silica gel TLC plate after spraying with hydrazine. Detection Aminco-Bowman spectrofluorimeter, with a TLC-scanning accessory. Ex = excitation, Em = emission, (b), Scan of a TLC analysis of a Sennokot tablet extract obtained with a Zeiss chromatogram scanner. Peaks 1 3 sennoside B 2 = sennoside A 3 = sennoside C. 

A fluorescence spectrum is characteristic of a given compound. It is observed as a result of radiative emission of the energy absorbed by the molecule. The observed spectrum does not depend on the wavelength of the exciting light, except that the spectrum will be more intense if irradiation occurs at the absorption maximum. The spectral intensity is called the quantum efficiency and is usually abbreviated as . The quantum yield or quantum efficiency, d>, which is solvent dependent, is the ratio Approximate values of quantum efficiencies are as follows naphthalene, 0.1 anthracene, 0.3 indole, 0.5 and fluorescein, 0.9. 

The appearance of a fluorescence spectrum is reminiscent of a UV-VIS spectrum. The fluorescence spectrum for a 3-substituted indole derivative is shown in Figure 6.1. The... 

TNP-ATP complex obtained by the single-molecule time-resolved spectroscopy, together with a fluorescence decay curve of TNP-ATP obtained by a bulk measurement. Both curves were well fitted to biexponential functions. The instrument-response function in 195-ps fwhm is also displayed. (B) Representative fluorescence spectrums of two individual enzyme-TNP-ATP complexes showing different emission peaks. A fluorescence spectrum of TNP-ATP obtained from a bulk measurement is also displayed for comparison. All spectrums were normalized to unity at their maximum. (From Ref. 18.)... 

The intensity, position of the emission wavelength, and lifetime are some of the observables that will characterize a fluorophore. Each fluorophore has its own fluorescence properties and observables. These properties are intrinsic to the fluorophore and are modified with the environment. A fluorescence spectrum is the plot of the fluorescence intensity as a function of wavelength (Figure 7.3). 

The fluorophores show different fluorescence spectra. A fluorescence spectrum reflects the electronic distribution of the molecule in the excited state Si and thus the structure of the molecule in this state. We notice also that ANS does not fluoresce in a phosphate buffer (i.e., a polar medium), which is not the case when it is bound to serum albumin. Thus, fluorescence depends not only on the structure of the fluorophore but also on its environment. Each fluorophore has its own spectral properties, and one should be careful not to generalize a rule for all fluorophores, although most of the fluorophores share common rules. 

Figure 9.7 Experimental fluorescence emission spectrum of a mixture of L-tyrosine and L-tryptophan in water (line, spectrum a) and that approximated using Equation (9.1) ( , spectrum b). Substracting spectrum (b) from (a) yields a fluorescence spectrum (c) characteristic of tyrosine. Xex =260 nm.

The results obtained are identical to many data obtained by different authors. However, one should remember that the literature also shows a fluorescence spectrum of bound ethidium bromide located at 605 nm to the difference of the peak observed for free ethidium bromide (see, e.g. the fluorescence excitation and emission spectra published by Molecular Probe) (Figure 12.5). However, this is not always observed, as is the case here. 

Also, the Phe-64 -> Leu and Ser-65 —> Thr mutant shows higher fluorescence parameters than that of the wild GFP. Excitation at 458 nm yields a fluorescence spectrum with two peaks at 512 and 530 nm. The fluorescence properties of this enhanced green fluorescent protein (EGFP) were found to be similar to the recombinant glutathione S-transferase-EGFP (GST-EGFP) protein, expressed in Escherichia coli (Cinelli etal. 2004). 

The 139La nucleus has a spin of 7/2 the Fermi contact hyperfine interaction is large in the B state and very large in the X state. Consequently the B -> A fluorescence spectrum exhibits a distinctive hyperfine structure, an example of which... 

The multi wavelength fluorescence detector consists of two monochromators, the first that selects the wavelength of the excitation light and the second disperses the fluorescent light and provides a fluorescence spectrum or allows the separation to be monitored at a selected fluorescence wavelength,... 

Figure 6. (a) Fluorescence spectrum of a mixture of naphthalene, phenanthrene, anthracene, perylene, ana tetracene (Xga. = 258 nm). (b) Synchronous signal (AX = 3 nm) of the same mixture. 

Direct observation of fluorescence from higher singlet states of benzene and some methyl derivatives has recently been achieved by Hirayama, Gregory, and Lipsky (247). Using apparatus capable of detecting fluorescence yields as low as 10 they recorded the emission spectra from oxygenated solutions of pure benzene and other aromatics excited at 184.9 nm. Subtraction of the tail of the residual S, emission gives a fluorescence spectrum with approximately 235 nm and = 8 x 10 for... 

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