Fluorescence temperature curve

Fluorescence temperature curves for the two biotypes of Solanum nigrum. 

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.

Weller24 has estimated enthalpies of exciplex formation from the energy separation vg, — i>5 ax of the molecular 0"-0 and exciplex fluorescence maximum using the appropriate form of Eq. (27) with ER assumed to have the value found for pyrene despite the doubtful validity of this approximation the values listed for AHa in Table VI are sufficiently low to permit exciplex dissociation during its radiative lifetime and the total emission spectrum of these systems may be expected to vary with temperature in the manner described above for one-component systems. This has recently been confirmed by Knibbe, Rehm, and Weller30 who obtain the enthalpies and entropies of photoassociation of the donor-acceptor pairs listed in Table XI. From a detailed analysis of the fluorescence decay curves for the perylene-diethyl-aniline system in benzene, Ware and Richter34 find that... 

At T = 77 K in MTHF, the kinetics of fluorescence decay of P-L-Q with a bridge containing one bicyclo[2.2.2]octyl is of a non-exponential character. This effect can be explained by the coexistence in the frozen solution of several rotational conformations of the P-L-Q molecule (rotation of the porphyrin fragment around the a bond in its meso position is meant here). The characteristic time of the fluorescence decay for the predominant portion of the P-L-Q particles at 77 K, r 1.1 x 10 1°s, virtually coincides with the value of r = l/k(e1 at 298 K, i.e. the rate of tunneling from P to Q is independent of temperature. The exponential character of the fluorescence decay curve at 298 K indicates that, at this temperature, the rate of rotation exceeds k(e1. ... 

Fig. 9. (i) Fluorescence decay curve (solid lines) for Rhodamine B (1 X 10 6 M, room temperature) (a) linear (b) semi-log. (ii) fluorescence decay curves (solid lines) for Rhodamine B (1 X 1CT6 M, room temperature) in the presence of 1.2 M KI (a) linear, (b) semi-log. The laser excitation pulse profile is shown by the broken lines. The time scale calibration of 64.1 ps per channel was derived from the 13.020 ns spacing between the mode-locked laser pulses. (After ref. 54.)... 

For an experimental demonstration of the capabilities of this system, Taylor et al. [69] studied the dual fluorescence decay of frans-stilbene as a function of temperature between —10 and 30° C. The fluorescence comprised two components, a short one varying between 125 and 64 ps and a longer one varying from 690 to 1450 ps over the range of temperatures studied. Typical fluorescence decay curves are shown in Fig. 21. The fluorescence decay curves were recorded over a total integration time of 2 s which represented a summation of 3 x 108 fluorescence decay profiles. The fluorescence profile of a single-shot would not be observable above the noise level. 

Fig. 13. Reflectance spectrum of MgO after outgassing at various temperatures and exposure to 133 nm2 (1 Torr) oxygen at room temperature to quench fluorescence solid curve, outgassed at 773 K dotted curve, outgassed at 923 K dashed curve, outgassed at 1073 K. [Figure according to Zecchina et at. (146).]...

Experimentally it was shown that with very early gates (At 0, 6t = 3 nsec) the fluorescence at room temperature in methylene chloride solution was principally monomer emission with some exclmer contribution (Figure 13) (42). Late-gated spectra (At 45 nsec, 6t 3 nsec) showed only exclmer fluorescence, as Figure 13 shows. The results show that exclmer dissociation in this polymer, (k j), can thus be ignored in the analysis of the data. Figure 13a shows fluorescence decay curves monitored at 273 nm (purely monomer) and 385 nm (purely exclmer). The curves can be fitted to decay functions of the form... 

The lifetime data of PS differ from laboratory to laboratory, because the fluorescence decay curve reflects not only the polymer type and solvent, but the processes of preparation, i.e., temperature, quality of the solvent, etc. 

Fig. 4 V versus V/s plots of low temperature fluorescence induction curves of the same sample. The insert shows that all curves behave as a higher order hyperbolic function in the V versus s plot with n s 1 curve(l), n > 1 curve (3) and n < 1 curve (2) and (4).

Fluorescence induction kinetics was measured at room temperature with a modified Aminco spectrophotometer in the presence of 20 mM DCMU after 5 min of dark adaptation. Relative rate of pheophytin anion photoaccumulation in PSII was estimated from the analysis of the fluorescence quenching curve in the presence of 20 mM dithionite (in 50mM Tricine, pH 7.8). 

GENETIC VARIATION AND DIVERSITY OF LOW TEMPERATURE INDUCED DAMAGES IN MAIZE SEEDLINGS AS ASSESSED BY CHLOROPHYLL FLUORESCENCE INDUCTION CURVES. 

Maize seedlings were grown in a phytotron programmmed for a 16hr photoperiod (300 pE.m-. s i) and a 25 C/15 C day/night temperature. Fluorescence induction curves were obtained from DCMU infiltrated leaves using a laboratory-made fluorometer. The wavelength of maximum emission was 592 nm. The fluorescence was measured at 685 nm. 

Genetic Variation and Diversity of Low Temperature Induced Damages in Maize Seedlings as Assessed by Chlorophyll Fluorescence Induction Curves 671... 

The energy transfer mechanism in dilute systems has been summarized by Watts (1975). At high donor concentrations and at elevated temperatures the donor-donor transfer may be appreciable. The fluorescence decay curves of the donors behave differently in the two cases mentioned above. If we write the donor-acceptor transfer rate as a R and the donon-donor rate as b R where R is the separation between the interacting ions and s equals 6, 8, and 10, for dipole-dipole, dipole-quadrupole, and quadrupole-quadrupole interactions, respectively, then two limiting cases can be considered (i) h/a = 0, where donor-donor interaction is absent, and (ii) b a>l, where donor-donor interaction is predominant. In the former case the decay curve of the donor fluorescence is nonexponential, being the sum of the decay of an isolated donor ion and the energy transfer to various accepted ions characterized by the factor exp(-Af ). In the opposite limit, which corresponds to rapid donor-donor transfer, the decay is exponential at all times, with a rate equal to the total donor-acceptor transfer... 

Only information about the photophysical properties of meso A5 has been reported. The fluorescence spectrum of meso A5 in isooctane at room temperature shows predominant broad excimer emission with maximum at 480 nm (Ijv/Ij =23). Lowering the temperature de creases the excimer emission (Ij /Im 0.08 at 183 K). The fluorescence decay curves of meso A5 in the monomer region (377 nm) are analyzed as the sum of a two exponential function. The decay curves in the excimer region are fitted to a triple exponential function. One of the exponents has a negative preexponential factor. The complex photophysical behaviour of meso A5 cannot be interpreted with the one ground state conformation present if one does not include the possibility of aryl rotamers and consequently the existence of partial overlap excimers. The existence of more than one excimer is confirmed when fluorescence decay curves in function of wavelength of detection in the excimer region were analyzed. The shorter... 

The fluorescence spectra of meso and racemic B5 show large differences (Collart et al., 1983). Both compounds emit excimer fluorescence but the ratio Id/1j at room temperature equals 18 and 1.15 respectively for meso B5 and racemic B5. Only the fluorescence decay curves of meso B5 are reported (Collart et al., 1985). The photophysical behaviour of... 

Standardizing the Method Equations 10.32 and 10.33 show that the intensity of fluorescent or phosphorescent emission is proportional to the concentration of the photoluminescent species, provided that the absorbance of radiation from the excitation source (A = ebC) is less than approximately 0.01. Quantitative methods are usually standardized using a set of external standards. Calibration curves are linear over as much as four to six orders of magnitude for fluorescence and two to four orders of magnitude for phosphorescence. Calibration curves become nonlinear for high concentrations of the photoluminescent species at which the intensity of emission is given by equation 10.31. Nonlinearity also may be observed at low concentrations due to the presence of fluorescent or phosphorescent contaminants. As discussed earlier, the quantum efficiency for emission is sensitive to temperature and sample matrix, both of which must be controlled if external standards are to be used. In addition, emission intensity depends on the molar absorptivity of the photoluminescent species, which is sensitive to the sample matrix. 

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