Calcium fluorescent probes

Figure 4.7 Changes in intraceiiuiar calcium in cultured rat ventricular myocytes exposed to oxidant stress. Calcium was measured using the fluorescent probe Fura>2. The ratio of the Fura-2 fluorescence measured at 340 and 380 nm excitation is shown and this is proportional to the intracellular calcium concentration. The fast-speed traces shown (note the 3.5 s time-scale) were recorded after various durations of oxidant stress. Myocytes under control conditions (before t = 0) show spontaneous calcium transients. These transients decreased in frequency with oxidant stress until cells failed to show spontaneous activity but continued to maintain a low intracellular calcium.

Calcium sensors are merely representative of a much wider class of ion sensors, albeit probably the best understood. Fluorescent probes have now been developed for a wide range of metal ions of biological interest, particularly sodium, potassium, magnesium, and zinc. 

Johnson, J.D., Collins, J.H., and Potter, J.D. (1978) Dansylaziridine labeled troponin C. A fluorescent probe of calcium ion binding to the calcium ion-specific regulatory sites./. Biol. Chem. 253, 6451. 

Fig. 10.22. Chelating PCT sensors for calcium and magnesium ions (PCT-11 and PCT-12 Grynkiewicz G. et al. (1985) J. Biol. Chem. 260, 3440. PCT-13 and PCT-14 Haugland R. P., Handbook of Fluorescent Probes and Research Chemicals, 6th edn, Molecular Probes, Inc., Eugene, OR).

For practical applications it is better to use fluorescent probes excitable at high wavelengths, so that autofluorescence of the sample (especially biological samples) does not interfere. Calcium indicators based on fluorescein and rhodamine fluorophores(70) fulfill this requirement and are thus more convenient for fluorescence... 

In biomedical applications, the ranges of ion concentration are higher by several orders of magnitude. For instance, the abovementioned calcium probes for living cells cannot be used because the dissociation constant is so low that they would be saturated. Special attention is thus to be paid to the ionophore moiety to achieve proper selectivity and efficiency of binding. For instance, at present there is a need for a selective fluorescent probe for the determination of calcium in blood which could work in the millimolar range in aqueous solutions so that optodes with immobilized probes on the tip could be made for continuous monitoring calcium in blood vessels. 

Fluorimetric methods have proven useful for the assay of metal ions in solution 1 e.g., in vivo studies of calcium-selective fluorescence probes have been reported by... 

K. M. Hirshfeld, D. Toptygin, B. S. Packard, andL. Brand, Dynamic fluorescence measurements of two-state systems Applications to calcium chelating probes, Anal. Biochem. 209, 209-218 (1993). 

Characterization of Inverted Micelles of Calcium Alkarylsulfonates by Some Pyrene Fluorescence Probes... 

Pyrene carboxaldehyde and a series of pyrene carboxylic acids were found useful as fluorescence probes in describing the constitution of inverted micelles of certain calcium alkarylsulfonates in hydrocarbon media. 1-Pyrene carboxaldehyde is a convenient probe for studying the particle sizes of micelles in the region of lOOA. A series of graded probes, pyrene carboxylic acids with varying alkyl chain length, have been used to determine internal fluidity and micro-polarity as a function of distance from the polar core of these Inverted micelles. Pyrene exclmer to monomer fluorescence intensity ratio and fluorescene lifetime provided the means of measurement of internal fluidity and micropolarity, respectively. 

Pyrene Carboxaldehyde in Calcium Alkarylsulfonates. Our work shows that 1-pyrene carboxaldehyde as a fluorescent probe for the sulfonate systems behaves very much the same as rhodamine B (1 ) and anillnonaphthalene sulfonate (2), whose fluorescence intensities in hydrocarbon media are enhanced in the presence of inverted micelles. However, the intensity Increase observed with AOT was considerably less than that observed with the sulfonates. It is speculated that... 

Figure 1. (Bottom) Diagram of the electrostatic potential adjacent to a membrane bearing a positive charge. The zeta potential is the potential at the hydrodynamic plane of shear, which should be about 2 A from the surface of the membrane. (Top) Schematic of the location of the probe molecules used to detect the potential produced by the adsorption of calcium and other alkaline earth cations to membranes formed from PC. The divalent cation cobalt and the amphipathic, anionic, fluorescent probe TNS will sense the potential at the interface. The non-actin-Rf complex will sense the potential in the center of the membrane.

Flue gas desulfurization The injection of calcium or other sorbents to remove sulfur from flue gases. Fluorescent probe A chemical that can produce light when being acted upon by a source of energy. Fluvial A term used to describe structures, organisms, sediments, and other features associated with rivers. 

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. 

Fluorimetric methods have proven useful for the assay of metal ions in solution (i) for example, in vivo studies of calcium-selective fluorescence probes have been reported by Tsien (2). Most such analytical methods reported to date involve complexation of metal ions with aromatic heterocyclic ligands ("intrinsic" fluoroionophores). In 1977, Sousa described the synthesis of naphthalene-crown ether probes (Figure 1) in which the fluorophore 7C-system is insulated from the... 

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