Chelates fluorescence

Different lanthanide metals also produce different emission spectrums and different intensities of luminescence at their emission maximums. Therefore, the relative sensitivity of time-resolved fluorescence also is dependent on the particular lanthanide element complexed in the chelate. The most popular metals along with the order of brightness for lanthanide chelate fluorescence are europium(III) > terbium(III) > samarium(III) > dysprosium(III). For instance, Huhtinen et al. (2005) found that lanthanide chelate nanoparticles used in the detection of human prostate antigen produced relative signals for detection using europium, terbium, samarium, and dysprosium of approximately 1.0 0.67 0.16 0.01, respectively. The emission... 

Johnson, D.K., S.M. Combs, J.D. Parsen, et al. 2002. Lead analysis by anti-chelate fluorescence polarization immunoassay. Environ. Sci. Technol. 36 1042-1047. 

Ca2+ levels, with one of the intracellular calcium-chelating, fluorescent probes, quin-2, fura-2 or indo-1, demonstrates that, in both cases, there is a rapid rise in intracellular Ca2+ as this ion is released from intracellular stores. Analysis of stimulated B lymphocytes, using the probe fura-2, indicates that if Ca2+ in the external medium is removed the intracellular Ca2+ level returns to basal levels in 5 to 7 minutes, but if there is Ca2+ present in the external media a sustained increase in intracellular Ca2+ is detected [36]. Such analysis suggests the opening of a plasma membrane calcium channel but the nature of the channel or mechanism of its opening are not presently known. It is possible that the opening of this channel could be stimulated by one of the inositol phosphates. 

HPLC detection Estrogens Lanthanoid chelate fluorescent labels, detection limits in the picogram range... 

A single 337-nm flash (<1 ns) released sufficient bradykinin to excite the BK2 receptors on single rat sensory neurons, which dramatically increased the intracellular calcium concentration measured with Indo-1, a Ca +-chelating fluorescent indicator. The quantum efficiency of bradykinin appearance was idependently determined to be 0.22, as shown in Table 69.12. 

Many hydrazones and azines are colored and useful as dyestuffs. Examples are 2-hydroxynaphthazine, a yellow fluorescent dye (Lumogen LT Bright Yellow), and the pyridon—azino—quinone class of red-violet dyes. Numerous hydrazine derivatives are antioxidants and stabilizers by virtue of their reducing and chelating powers. 

Flumequine is a representative of fluoroquinolones which are high-effective antimicrobial medicines used as fodder supplements in cattle-breeding. This causes the necessity in effective testing techniques to detenuine the content of flumequine in meat products. Fluorimetric determination based on sensitized luminescence of fluoroquinolone chelates with lanthanides is a promising one. The literature lacks information of flumequine detemiination with the aid of sensitized fluorescence. 

The reaction takes place with the formation of fluorescent chelates according to the following scheme ... 

Discussion. This method is based upon the formation of a fluorescent chelate between calcium ions and calcein [fluorescein bis(methyliminodiacetic acid)] in alkaline solution.29 The procedure described below30 has been employed for the determination of calcium in biological materials.31 ... 

Intracellular calcium elevation is monitored by fluorescent chelators developed by Tsien and coworkers. These indicators are loaded into cells the same way the pH indicators are. With Quin-2 (14), one of the first such probes developed, the quantum yield increases about fourfold when Ca binds to it. The second generation of Ca probes, Indo-1 and Fura-2 (15), are now being widely used in a variety of cell types. These probes are in most cases... 

Figure 7. Sensitivity of the FMLP-induced calcium signal to removal of extracellular calcium. Indo-l-loaded neutrophils were stimulated with 10 M FMLP in a medium of normal osmolality (320 mosmol/kg) and indo-1 fluorescence was recorded as described in Figure 6. Trace 1 Cells in a medium with normal calcium (1.5 mN). Trace 2 EGTA added to chelate extracellular calcium before stimulation extracellular calcium (1.5 milf) readded 70 s after stimulation. Trace 3 Cells in a medium with normal calcium EGTA added 70 s after stimulation to chelate extracellular calcium.

Wetai Ion Analysis. We have reported a sensitive trace-metal analysis based upon HPLC separation of p-aminophenyl EDTA chelates and fluorescence detection by postcolumn reaction with fluorescamine (23). An application of the pyridone chemistry already discussed leads to a fluorescent-labeled EDTA (VIII). 

We have developed reverse-phase ion-pairing HPLC separations of substituted EDTA metal chelates of several transition metals (including Cd, Zn, Fb, and Hg) and several lanthanides (La, Ce, Eu, Dy, Er, Yb, Lu). Detection levels of these chelates are currently being assessed. A sensitive metal ion analysis employing an inherently fluorescent EDTA seems feasible. 

Figure 9. Typical fluorescence signals obtained from a suspension of isolated rat cardiac myocytes after the application of maitotoxin (MTX). The arrow indicates the addition of MTX (10 g/mL), a detergent Emulgen 810 (1%), which frees all vesicular Ca , or EGTA (3.5 mM), a chelator that removes all free Ca in the cuvette. The intensity of Quin 2 fluorescence is expressed in arbitrary units. (Reproduced with permission from Ref. 20. Copyright 1987 Elsevier)...

Dorn, 1. T., Neumaier, K. R. and Tampe, R. (1998) Molecular recognition of histidine-tagged molecules by metal-chelating lipids monitored by fluorescence energy transfer and correlation spectroscopy. ]. Am. Chem. Soc 120, 2753. 

Iron uptake by bacteria at sites of lateral root emergence has been further confirmed using another technique employing 7-nitrobenz-2-oxa-l,3-diazole-desferrioxamine B, which is a derivitized siderophore that becomes fluorescent after it is deferrated (78). In this case, iron uptake from the siderophore ferrox-amine B was a.ssociated primarily with microbially colonized roots, but both plant and iron uptake from this chelate occurred in the regions just behind the root tips. 

Miyahara, T., Kitamura, H., Narita, K., and Toyo oka, T., Ion-exchange chromatography of aluminum using 3-carboxy-2-naphthylamine-N,N-diacetic acid as a fluorescent post-column chelating reagent, Biomed. Chromatogr., 13, 70, 1999. 

The interest in colour indicators has recently increased as they are used for the direct determination of pH (acid-base indicators) and free calcium ions (fluorescent derivatives based on the calcium chelator EGTA as metallochromic indicators) in biological systems at cellular level. 

This dye fluoresces after binding Pb+2 and Ca+2 lead is considered an interferant to the determination of calcium by this approach. However, by complexing the divalent lead ion with the heavy metal chelator TPEN (N,N,N ,N -tetrakis(2-pyridylmethyl)ethylene-diamine) prior to the addition of the fluo-3, the fluorescent... 

Batuman V, Wedeen RP, Bogden JD, et al. 1989. Reducing bone lead content by chelation treatment in chronic lead poisoning An in vivo X-ray fluorescence and bone biopsy study. Environ Res 48 70-75. 

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