Fluorescence curves

The mathematical treatment of each of the fluorescence curves shown in O Figure 5-5 is identical. First nonspecific effects must be subtracted so that in each case we have a relationship between the concentration of ligand and the change in fluorescence. The binding equation is formally identical to the terminology for... 

Fig. 26. Sensitized anti-Stokes delayed fluorescence from anthracene.60 Normal fluorescence (curve 1) and delayed fluorescence (curve 2) from a solution containing 10- Af proflavine hydrochloride and 5 X 10-4M anthracene in ethanol excited by 436 m/ , 3 X 10-4 einstein liter-1 sec.-1 absorbed. Curve 1 at a sensitivity 3000 times less than curve 2. Temperature was — 66°C. 3°C.

Thus, we have measured fluorescence decay dynamics of w.-t. PYP and also various site-directed mutants and those fluorescence curves can be well reproduced by the following equation with two coupled oscillating modes. 

The aggregation numbers Nagg is determined as 27 for C1-(EO)53-C4-VB and 38 for Cr(EO)53-C7-VB micelles by analysis of fluorescence curves. A micelle formation mechanism is proposed for nonionic polymeric surfactants with weakly hydrophobic groups. At low concentrations of PEO macromonomers, large loosely aggregated structures involving the PEO chains are formed. At higher concentrations normal micelles form. These are star-shaped, with a hydrophobic core surrounded by a corona of PEO chains. 

When pure compounds are chromatographed, the fractions are directly analyzed by an Aminco spectrophotofluorometer. Activation and fluorescence spectra of each metabolite have been determined and concentration-fluorescence curves show that the sensitivity is adequate even at 0.01 pg for at least four compounds. For kynurenine and 3-hydroxykynurenine, which are less fluorescent, colorimetric readings are preferred. 

Of the 869 families derived from plants collected in five populations (Table II), 33 showed at least one seedling with an intermediary fluorescence curve (Figure 1 (21)). These seedlings proved later to have the mutated psbA gene at Position 264 (19) and were moderately resistant to atrazine. They were called Type I (for intermediate level of resistance). The 33 mother plants and their corresponding seed families were called Sp. because they were special susceptible plants that produced mutant plants. 

Figure 1.Fluorescence curve of whole leaves of the three phenotypes of Chenopodium album after a one night incubation with 30 ppm atrazine...

We tested the response of various fluorescence parameters to radiation. Among all tested values (Fo, Fm> Fy/Fm, area, Fj, Fp etc.) the modification of the area over the fluorescence curve was more relevant at the low radiation dose exposure (Fig. 9). 

An accurate fluorescence lifetime measurement normally requires measurements of the fluorescence and the instrument response function (IRF). The lifetime or the lifetime components of the decay function are then obtained by deconvolution of the fluorescence curve from the IRF [389]. 

For fluorescence lifetimes much shorter than the IRF width, the shapes of the recorded IRF and the recorded fluorescence curve are almost identical. Provided the same number of photons, N, is recorded both in the IRF and the fluorescence curve, the standard deviation,, of the calculated fluorescence lifetime, t, is ... 

The real-time PCR fluorescence curve generated by the sequence detection system is composed of four distinct phases. When PCR product and reporter signal accumulate beyond background fluorescence levels, the reaction enters the exponential detection phase. At this point the amplification plot crosses a user-defined detection threshold which is set above the background fluorescence noise, preferable at the beginning of the exponential phase. The fractional cycle number at which the reaction crosses the threshold (C ) is related inversely to the initial template DNA concentration. As PCR products continues to accumulate, the ratio of Taq DNA polymerase to amplified products decreases, resulting in nonexponential accumulation of amplicons. At this point the reaction enters the linear phase. Once PCR product ceases to accumulate due to assay depletion, AR values remain relatively constant and the reaction enters the plateau phase. 

FIGURE 7.6 Fluorescence curves for samples of cattle, pig, lamb, goat, chicken, turkey, and duck using the MYw primer-probe system. C/s are listed in Table 7.6. 

Figure 5.46 Absorption and fluorescence spectra of anthracene and quinine Curve A, anthracene absorption Curve B, quinine absorption Curve C, anthracene fluorescence Curve D, quinine fluorescence. (From Guilbault, used with permission.)...

Figure 2. QD PL (curve 1, Xrec= 481 nm) and extra-ligand H2P(p-Pyr)4 fluorescence (curves 2 and 3, Xrec= 714 nm) relative intensities, I(x)/I(0) as a function of the dimer (ZnOEPEPh molar ratio for mixture QD ILPip-Pyuf , x = 0.45, curves 1 and 2) and individual ligand H2P(p-Pyr)4 (curve 3) solutions (toluene, 295 K, A x = 465 nm). Right Schematic presentation of...

The enzyme/substrate (tyrosinase/wool hydrolysate) mixture (20 pL) was diluted widi 980 pL of distilled water, 70 pL of ethylenediamine, and 50 pL of 2M etfaylenediainine dihydrochloride (pH 11). The mixture was incubated at 50°C for 2 h in die dark, and then the fluorescence intensity was measured using a UVA IS spectrofluorom o (Tecan). The excitation and emission wavelengdis were at 420 and 543 nm, respectively. The concentrations of the DOPA residue in the preparations were estimated using a standard fluorescence curve of DOPA [8]. For the Dopa Quinone (DQ) quantification M6TH (3-methyl-2-benzothiazolinone hydrazone hydrochlcnide monohydrate) was used. MBTH reacts with DQ to form a pink pigmoit widi Xnm at 505 nm. The assay solution was prepared by mixing 480 pL of the en me/substrate reaction mixture, 980 pL of 4.3% (v/v) DMF (dimethyl formamide) in distiUed water, and 580 pL of 20.7 mM MBTH. The total volume was 2 mL. Tbe reacticm mixture was incubated at 25 C for 10 min before the absorbance measurement (at 505 nm) [8]. 

The kinetics of the change of area above the complete fluorescence curves for these two experiments have been analysed and the results are displayed in Table 1. We found four kinetic phases to be present which is two more than usually reported and we will refer to them as a,B,r, and S going from the fastest to the slowest. 

The sigmoidal character of the fluorescence curve was enhanced by the far-red pretreatment [Fig.l] and this was reflected in the more concave appearance of the corresponding a phase. These findings suggest that there was a smaller degree of connectivity between the a phase units after dark pretreatment, which may have arisen because of the incomplete oxidation of electron acceptors. This would be in agreement with the faster apparent rate constant. 

The principles of the quantitative analysis of the fluorescence curve obtained from DCMU infiltrated leaves have been described by Malkin et al.(3). They demonstrate that the surface concentration of PSII reaction centres could be calculated according to ... 

Figure 3. Fluorescence intensity of two different molecules as a function of the polarization of the exciting light. The molecules are located near the center of site Oj. The fluorescence intensity shows a sinusoidal modulation. For molecule B the maximum of the fluorescence intensity is shifted with respect to molecule A. There is no position were the fluorescence of molecule B vanishes completely. The fluorescence curves are fitted to a sinusoidal function. The fit parameters yield the values for and Figure adapted from Ref. 1.

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