Room-temperature fluorescence spectrum

Figure 1. (a) Room-temperature fluorescence spectra of benzo(a)pyrene on 80% a-[Pg.158]

Such a qualitative conclusion is supported by the observation that the room-temperature fluorescence spectrum of BMPC in alcohols (Fig. 8) is a good mirror image... 

Fig. 3.4. Potential energy diagram of DMABN (top) the reaction coordinate contains both solvent relaxation and rotation of the dimethylamino group. Room temperature fluorescence spectrum in hexane and tetrahydrofurane (bottom) (adapted from Lippert et al., 1987).

In any case, our results clearly demonstrate that the room temperature fluorescence spectrum of chlorophyll-proteins differs according to the state of both the donor and acceptor sides of PS II reaction center. 

The ESR spectrum of the pyridazine radical anion, generated by the action of sodium or potassium, has been reported, and oxidation of 6-hydroxypyridazin-3(2//)-one with cerium(IV) sulfate in sulfuric acid results in an intense ESR spectrum (79TL2821). The self-diffusion coefficient and activation energy, the half-wave potential (-2.16 eV) magnetic susceptibility and room temperature fluorescence in-solution (Amax = 23 800cm life time 2.6 X 10 s) are reported. 

The room temperature Raman spectrum excited in pre-resonance conditions [351 indeed shows bands at 169 cm-1 and 306 cm, which are in agreement with the modes observed in the fluorescence spectrum and that have been assigned by ab initio calculations to totally symmetric vibrations jl3). 

Figure 3. Three-dimensional plot of the room-temperature fluorescence of a mixture of 500 ng each of benzo(a)pyrene and benzo(e)pyrene on 80% q-cyclodextrin-NaCl. Numbers along dashed lines show the approximate wavelengths (nm) represented by these lines. The excitation wavelength was varied from 250 nm (front spectrum) to 370 nm (back spectrum) at 2-nm increments. Benzo(a)pyrene emitted from approximately 380 nm to 540 nm, and benzo(e)pyrene emitted from 365 nm to 505 nm.

Room-temperature fluorescence (RTF) has been used to determine the emission characteristics of a wide variety of materials relative to the wavelengths of several Fraunhofer lines. Fraunhofer lines are bands of reduced intensity in the solar spectrum caused by the selective absorption of light by gaseous elements in the solar atmosphere. RTF studies have recently included the search for the causes of the luminescence of materials and a compilation of information that will lead to "luminescence signatures" for these materials. For this purpose, excitation-emission matrix (EEM) data are now being collected. 

Examinations of other physical properties of pyridazine include the ESR spectrum of pyridazine radical anion (obtained with pyridazine and sodium or potassium in dimethoxyethane or tetra-hydrofuran, the self-diffusion coefficient and activation energy, the half-wave potential (-2.16V), and magnetic susceptibility. Pyridazine was reported not to fluoresce and no luminiscence could be observed even under very long exposures. More recently, room-temperature fluorescence in solution is reported to be at 23,800 cm (max.), with a life time of 2.6 x 10 . ... 

Figure 2.20. Absorption (black line) and fluorescence spectra of the AXFF in Ar-saturated cyclohexane at room temperature. Fluorescence spectra were obtained during the 266- and 355-nm (dark gray line) or 266- and 532-nm (light gray line) two-color two-laser flash photolysis. The absorption spectrum was obtained during one-laser photolysis (266-nm, black line) of AX (4.0 x 10 4M). The second laser irradiation was at 1 ps after the first laser pulse. All the fluorescence spectra of AXFb were normalized with the corresponding absorption peaks. Inset Kinetic traces of the fluorescence intensity of AXH- at 460 and 645 nm.

This study has been carried out in order to detect modifications of the spectral properties of the PS II chiorophyl1-proteins which might occur during the photoactivation. For this purpose we have analyzed the room temperature emission spectrum of intact flashed leaves in the course of this process. Our results show that a quenching of the fluorescence around 693 nm occurs along with the photoactivation. 

Rgure 4 Fluorescence emission spectra of 20 ng pyrene on a C-18 modified silica HPTLC plate. Upper spectrum lamp excitation at room temperature. Lower spectrum laser excitation at 363.5 nm 7=10K. 

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.

Photophysical Processes in Pol,y(ethy1eneterephthalate-co-4,4 -biphenyldicarboxyl ate) (PET-co-4,4 -BPDC). The absorption and luminescence properties of PET are summarized above. At room temperature the absorption spectrum of PET-co-4,4 -BPDC copolymers, with concentrations of 4,4 -BPDC ranging from 0.5 -5.0 mole percent, showed UV absorption spectra similar to that of PET in HFIP. The corrected fluorescence spectra of the copolymers in HFIP exhibited excitation maxima at 255 and 290 nm. The emission spectrum displayed emission from the terephthalate portion of the polymer, when excited by 255 nm radiation, and emission from the 4,4 -biphenyldicarboxylate portion of the polymer when excited with 290 nm radiation. 

Fig. 7. UV.-absorption spectrum (in QH12 at room temperature) and fluorescence spectrum (in ether/pentane at 77 K) of an aryl alkyl thio-...

In contrast, at room temperature, the reconstructed fluorescence spectra were found to be identical to the steady-state spectrum, which means that solvent relaxation occurs at times much shorter than 1 ns in fluid solution. 

In 1971, adrenodoxin, an iron-sulfur protein with a single tyrosine residue and no tryptophan was shown to fluoresce at 331 nm upon 280-nm excitation at neutral pH/20 1 On cooling from room temperature to 77 K, the emission maximum shifts to 315 nm. The redox state of the iron does not have any effect on the tyrosine emission. From these results, an exciplex between the excited singlet state of tyrosine and an unidentified group was suggested as the cause of the anomalous emission energy/2031 Later studies have shown that the excitation spectrum is a red-shifted tyrosine spectrum, that removal of the iron to form the apoprotein has no effect on the emission, and that heat, low pH, guanidine hydrochloride, urea, and LiCl all cause the emission... 

Figure 3.2 shows the fluorescence and phosphorescence emission spectrum from tobacco mosaic virus coat protein. These spectra are fairly typical of the tryptophan emission spectra observed from proteins at room temperature. 

Differences between the spectra of fluorescence and phosphorescence are immediately obvious. For all tryptophans in proteins the phosphorescence spectrum, even at room temperature, is structured, while the fluorescence emission is not. (Even at low temperatures the fluorescence emission spectrum is usually not structured. The notable exceptions include a-amylase and aldolase, 26 protease, azurin 27,28 and ribonuclease 7, staphylococcal endonuclease, elastase, tobacco mosaic virus coat protein, and Drosophila alcohol dehydrogenase 12. )... 

Fig. 22 B. Exeitation spectrum at room temperature showing the intensity of delayed fluorescence of a naphthalene crystal as a function of the wavelength of the exciting light. The ordinate is proportional to the square of the singlet-triplet absorption coefficient. (From Avakian and Abramson, Ref.52))...

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