Luminescent intensity concentration

From figure follows, that in case of injection of small concentration of AO in it will be consume rather slowly, that results in slow variation of luminescence intensity during certain time. 

Fig. 3.2.7 Left panel Effects of temperature on the luminescence intensity and stability of the protein P from Meganyctiphanes. The initial light intensity was measured with F plus P in 5 ml of 20 mM Tris-HCl/0.15 M NaCl, pH 7.5, at various temperatures. In the stability test, P was kept at the indicated temperature for 10 min, then mixed with 5 ml of 25 mM Tris-HCl/1 M NaCl, pH 7.59, containing F, to measure initial light intensity. Right panel Effect of the concentration of salts on the light intensity of the luminescence of F plus P, in 25 mM Tris-HCl, pH 7.6, at near 0°C. In the case of NaCl, the light intensity decreased to about a half after 10 min. From Shi-momura and Johnson, 1967, with permission from the American Chemical Society.

Relationship between Ca2+ concentration and luminescence intensity. In the measurement of Ca2+ concentration with aequorin, the calibration of the relationship between Ca2+ concentration and luminescence intensity is essential. However, the application of this relationship is complicated by the chelator used to set the Ca2+ concentration, for the reason noted above. To minimize the complication, we used only a minimum amount of EDTA to protect aequorin in the measurements to obtain the relationship between Ca2+ -concentration and light intensity, and plotted the data as shown in Fig. 4.1.7 (Shimomura and Johnson, 1976). The concentration of EDTA was... 

Fig. 4.1.8 Influence of various calcium chelators on the relationship between Ca2 " concentration and the luminescence intensity of aequorin, at 23-25°C (panel A) in low-ionic strength buffers (I < 0.005) and (panel B) with 150 mM KC1 added. Buffer solutions (3 ml) of various Ca2+ concentrations, pH 7.05, made with or without a calcium buffer was added to 2 pi of 10 pM aequorin solution containing 10 pM EDTA. The calcium buffer was composed of the free form of a chelator (1 or 2mM) and various concentrations of the Ca2+-chelator (1 1) complex to set the Ca2+ concentrations (the concentration of free chelator was constant at all Ca2+ concentrations). The curves shown are obtained with 1 mM MOPS (A), 1 mM gly-cylglycine ( + ), 1 mM citrate (o), 1 mM EDTA plus 2mM MOPS ( ), 1 mM EGTA plus 2 mM MOPS ( ), 2 mM NTA plus 2 mM MOPS (V), and 2 mM ADA plus 2 mM MOPS (A). In the chelator-free buffers, MOPS and glycylglycine, Ca2+ concentrations were set by the concentration of calcium acetate. Reproduced with permission, from Shimomura and Shimomura, 1984. the Biochemical Society.

The second procedure is to measure the luminescence intensities at various Ca2+ concentrations and plot log (light intensity) against —log [Ca2+] for each aequorin. Examples of this method are shown in Fig. 4.1.14. This method provides more detailed information on the sensitivity of each aequorin. Generally, an increase in Ca2+ sensitivity shifts the curve to the left. 

Properties of the luciferases. According to Shimomura and Flood (1998) and Shimomura et al. (2001), all Periphylla luciferases L, A, B and C catalyze the oxidation of coelenterazine, resulting in the emission of blue light (Amax 465 nm). Luciferases B (40 kDa) and C (80 kDa) are apparently the dimer and tetramer, respectively, of luciferase A (20 kDa). The presence of a salt is essential for the activity of luciferase, and the optimum salt concentration is about 1M in the case of NaCl for all forms of luciferases. The luminescence intensity of luciferase L is maximum near 0°C, and decreases almost linearly with rising temperature, falling to zero intensity at 60°C the luminescence intensity profiles of luciferases A, B and C show their peaks at about 30°C (Fig. 4.5.3). The Michaelis constants estimated for luciferases A, B and C with coelenterazine are all about 0.2 xM, and that for luciferase L is 1.2 jiM. 

Luciferase-catalyzed luminescence of luciferin. Odontosyllis luciferin emits light in the presence of Mg2+, molecular oxygen and luciferase. The relationship between the luminescence intensity and the pH of the medium shows a broad optimum (Fig. 7.2.8). The luminescence reaction requires a divalent alkaline earth ion, of which Mg2+ is most effective (optimum concentration 30 mM). Monovalent cations such as Na+, K+, and NH have little effect, and many heavy metal ions, such as Hg2+, Cu2+, Co2+ and Zn2+, are generally inhibitory. The activity of crude preparations of luciferase progressively decreases by repeated dialysis and also by concentrating the solutions under reduced pressure. However, the decreased luciferase activity can be completely restored to the original activity by the addition of 1 mM HCN (added as KCN). The relationship between the concentration of HCN and the luciferase activity is shown in Fig. 7.2.9. Low concentrations of h and K3Fe(CN)6 also enhance luminescence, but their effects are only transient. 

Fig. 10.2.2 Influence of the concentrations of ATP, Mg2-1- and Ca2+ on the maximum luminescence intensity of the photoprotein of the millipede Luminodestnus. The luminescence reaction was started by mixing a solution of the photoprotein (A280 0.3, 10 pi) with 2 ml of 10mM Tris-HCl buffer, pH 8.3, containing either 1 mM MgCb plus various concentrations of ATP or 0.05 mM ATP plus various concentrations Mg2+ or Ca2+. From Shimomura, 1981, with permission from the Federation of the European Biochemical Societies.

E.coli recA y.luxCDABE strain were grown for 16-18 hours at 37°C in LB-broth in the presence of 20 pg/ ml of ampicillin. Immediately before the experiment the culture was diluted 1 20 by fresh culture medium and incubated until early log-phase. The grown biomass was mixed with AR solutions in final concentrations of ICfs, ICH n ICfs M, with used for their dilution with distilled water (control) and incubated for 60 minutes. The luminescence intensity of UV-irradiated E.coli recA lux and intact specimens were registered by plate bioluminometer LM OIT (Immimotech, Czech Rep.) in a real time. The number of viable cells was determined from the colony-forming units (CFU) on a surface of a LB-agar after the subsequent incubation within 24 hours at 37 °C. A quantitative estimation of an induction of the SOS-system calculated on formula... 

Organic acid fluorescence. In a similar manner to trace constituents, such as Mg, Sr and P, concentrations of organic acids present in speleothem calcite are sufficient to observe variation at temporal scales of less than annual in some cases (e.g.. Baker et al. 1993, Shopov et al. 1994). Organic acids (humic and fulvic) are formed in the soil by humification, and transported to the cave void by percolating waters where they are entrapped in precipitating carbonates. Under certain circumstances, where precipitation patterns are strongly seasonal and the nature of vadose percolation is such that seasonal mixing is incomplete, bands with different luminescent intensities can be differentiated after excitation with UV radiation. In other cases, bands are not observable but secular... 

When the transient effect is negligible, k can then be determined by measuring the luminescence intensities under steady state conditions and the lifetimes of the decay in both the absence and the presence of a scavenger at concentration c. Indicating the intensities by Ig and I, respectively, and the... 

Provided it is optically diluted, the relationship between a luminophore (= luminescence bearer ) concentration and the intensity of its emission is a linear one ... 

Fig. 11 Plot of the luminescence intensity of an aqueous solution of Au23 against the ions added externally to the solution. The concentration of Au23 was the same for all the experiments. Clusters showed specific reactivity toward Cu2+ ions with significant quenching of luminescence. Photographs of the aqueous solution of Au23 in the presence of externally added ions under UV light irradiation are also given. The photograph was collected immediately after the addition of metal ions [15]...

The dependence of knr on the value or concentration of a [Parameter], in the vicinity of the excited sensor, determines both the luminescence intensity and the excited state lifetime of the sensor. 

An important class of luminescence sensors are those based on the decrease of luminescence intensity and lifetime of the probes as function of analyte concentration. Assume that the probe intensity decays by a single exponential with an unquenched lifetime tq. If quenching occurs only by a dynamic (collisional) mechanism, then the ratio to/t is equal to Fq/F and is described by the classic Stern-Volmer equation... 

In principle, an increase in the concentration of a luminescent center in a given material should be accompanied by an increase in the emitted light intensity, this being due to the corresponding increase in the absorption efficiency (see expression (1.15)). However, such behavior only occurs up to a certain critical concentration of the luminescent centers. Above this concentration, the luminescence intensity starts to decrease. This process is known as concentration quenching of luminescence. 

Comparison of this luminescence intensity in different samples reveals that any correlation is absent any impurity concentration. Thus it was supposed that the mostly probable luminescence center is Ti, which presence is quite natural in Ti bearing benitoite. The wide occurrence of Ti " minor impurities in minerals was detected by EPR. Like the other d ions (V, Mo ), Ti ions occur often in minerals as electron center (Marfunin 1979). It may be realized in benitoite, which does have some natural exposure to gamma rays in its natural setting. There could be radiation centers, such as, for example, Ti + gamma ray + electron donor Ti + electron hole. Benitoite color does not change with gamma irradiation to quite high doses (Rossman 1997) but luminescence is much more sensitive compared to optical absorption and can occur from centers at such low concentration that they do not impact the color of a benitoite. 

Three hydrozincite samples with different blue luminescence intensities were analyzed by ICP-MS. The first one with the strongest emission has 2,000 ppm of Pb, the second with weaker luminescence has 600 ppm, while the last one, practically without emission, has only 35 ppm. Such strong correlation supports interpretation of a Pb " liuninescence center as responsible for the hydrozindte blue emission. In contrast, the Eu concentrations (another candidate for a liuninescence center) are very low and do not correlate with the intensities of the blue liuninescence. 

Luminescence intensity with very rare exceptions is much higher in artificial gemstones compared to natural counterparts. It may be explained by the fact that the activator contents are usually higher in laboratory made gems, while the quenching center concentrations are lower. 

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