Furaptra

Structural formula
	Furaptra, free acid
General
Surname	Furaptra
other names	Mag-Fura-2; 2- [6- (bis (carboxymethyl) amino) -5- (carboxymethyloxy) benzofuran-2-yl] -oxazole-5-carboxy acid;
Molecular formula	C 18 H 14 N 2 O 11 ; C 18 H 10 K 4 N 2 O 11 (tetrapotassium salt);
External identifiers / databases
PubChem	123839
ChemSpider	110382
Wikidata	Q1474822
properties
Molar mass	434.31 g mol −1 ; 586.68 g mol −1 (tetrapotassium salt);
Physical state	firmly
safety instructions
GHS hazard labeling ; no classification available
GHS hazard labeling ; no classification available
	As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Furaptra is a calcium sensitive fluorescent dye . It fluoresces in the absence of Ca ²⁺ and is suitable for measuring cellular changes in calcium concentration.

Physical Properties

Mag-Fura-5, a derivative of Mag-Fura-2.

Unbound Furaptra has an absorption maximum at 370 nm and an emission maximum at 511 nm; the molar extinction coefficient is ε (H ₂ O) = 22,000 M ⁻¹ cm ⁻¹ . The chelate complex formed with calcium ions is no longer fluorescent. The intensity of the fluorescence therefore decreases with increasing Ca ²⁺ concentration. A derivative of Furaptra, Mag-Fura-5, has an additional methyl group .

Compared to Fura-2 , Furaptra binds calcium ions approx. 200 times weaker, but magnesium ions approx. 2–2.5 times stronger. Alternatively, Fura-2, Calcein , Indo-1 and Aequorin can be used.

History and Applications

Furaptra was originally developed as an indicator to detect free, cytosolic magnesium (Mg ²⁺ ) in the cell. However, it has been shown that the affinity of Furaptra for Ca ^{2+ is} approx. 100 times higher than that for Mg ²⁺ . Finally, the fluorescent indicator is also suitable for determining the concentration of zinc (II) ions.

Furaptra is used as an indicator to detect changes in the calcium ion concentration in intact living cells, especially in the endoplasmic reticulum (ER). The fluorescent dye diffuses into the cell as an esterified form (Furaptra-AM) and is hydrolyzed to Furaptra by esterases . In the cell, it is distributed evenly in the cytoplasm as well as in the organelles , for example in the ER. However, cytosolic Furaptra is transported out of the cell by anion transporters in the cell membrane , while dye accumulated in organelles remains there for a long time.

Experimental

Furaptra was used to analyze the function of muscle fibers and the resulting change in the calcium ion concentration in the myoplasm . If a muscle that has been treated with the dye is electrically stimulated, the fluorescence of the dye initially decreases. After some time, the intensity of the fluorescence returns to its original value. The interpretation of this finding is that as a result of the electrical stimulation, the concentration of free calcium ions in the myoplasm increases and some of the ions are complexed by Furaptra. As a result, its fluorescence decreases. If the calcium ions are then taken up again into the sarcoplasmic reticulum , Ca ^{2+ is released} from Furaptra, whereupon the fluorescent dye regains its original intensity.

literature

James W. Putney Jr. (Ed.): Calcium Signaling. 2nd Edition. CRC Press, Boca Raton 2005, ISBN 0-8493-2783-0 , pp. 18-30.

Individual evidence

↑ This substance has either not yet been classified with regard to its hazardousness or a reliable and citable source has not yet been found.
↑ James W. Putney Jr. (Ed.): Calcium Signaling. 2005, p. 27.
↑ Manufacturer information for the tetrapotassium salt (M1290) on the Molecular Probes website .
↑ James W. Putney Jr. (Ed.): Calcium Signaling. 2005, p. 25.
^ B. Raju et al.: A fluorescent indicator for measuring cytosolic free magnesium. In: Am J Physiol. 256 (3 Pt 1) (1989), C540-C548, PMID 2923192 .
^ TJ Simons: Measurement of free Zn ²⁺ ion concentration with the fluorescent probe mag-fura-2 (furaptra). In: J Biochem Biophys Methods. 27 (1) (1993), pp. 25-37, PMID 8409208 .
^ MW Roe et al: Visualizing calcium signaling in cells by digitized wide-field and confocal fluorescent microscopy. In: Methods Mol Biol. 319 (2006), pp. 37-66; PMID 16719350 .
↑ M. Konishi et al: Myoplasmic calcium transients in intact frog skeletal muscle fibers monitored with the fluorescent indicator furaptra. In: J Gen Physiol . 97 (2) (1991), pp. 271-301, PMID 201658 .
^ Roger Eckert, David Randall, Warren Burggren, Kathleen French: Tierphysiologie. 4th edition. Georg Thieme Verlag, Stuttgart 2002, ISBN 3-13-664004-7 , p. 405f.

[NV-1] This substance has either not yet been classified with regard to its hazardousness or a reliable and citable source has not yet been found.

[2] James W. Putney Jr. (Ed.): Calcium Signaling. 2005, p. 27.

[3] Manufacturer information for the tetrapotassium salt (M1290) on the Molecular Probes website .

[4] James W. Putney Jr. (Ed.): Calcium Signaling. 2005, p. 25.

[5] B. Raju et al.: A fluorescent indicator for measuring cytosolic free magnesium. In: Am J Physiol. 256 (3 Pt 1) (1989), C540-C548, PMID 2923192 .

[6] TJ Simons: Measurement of free Zn ²⁺ ion concentration with the fluorescent probe mag-fura-2 (furaptra). In: J Biochem Biophys Methods. 27 (1) (1993), pp. 25-37, PMID 8409208 .

[7] MW Roe et al: Visualizing calcium signaling in cells by digitized wide-field and confocal fluorescent microscopy. In: Methods Mol Biol. 319 (2006), pp. 37-66; PMID 16719350 .

[8] M. Konishi et al: Myoplasmic calcium transients in intact frog skeletal muscle fibers monitored with the fluorescent indicator furaptra. In: J Gen Physiol . 97 (2) (1991), pp. 271-301, PMID 201658 .

[9] Roger Eckert, David Randall, Warren Burggren, Kathleen French: Tierphysiologie. 4th edition. Georg Thieme Verlag, Stuttgart 2002, ISBN 3-13-664004-7 , p. 405f.