The steady-state maintenance of disproportionate concentrations of inorganic cations and anions is a feature of living cells. Homeostatic regulation of these ionic gradients across different compartments is critical for most cellular functions. Measuring concentrations of these ions with both spatial and temporal resolution has become very critical in understanding the physiology of the cells in the research community. Ion probes provide a means of correlating ion channel activation with subsequent changes in intracellular ion concentration. Flux measured by these type of probes also reflects the cells’ membrane potential. We offer many ion probes which effectively measures respected ion efficiently.
Calcium Ion Detection
Calcium acts as a universal second messenger in a variety of cells. Numerous functions of all types of cells are regulated by Ca2+, thus calcium measurement is critical for various biological investigations. In the 1980s, Tsien and colleagues produced a variety of fluorescent indicators. Among them Indo-1, Fura-2, Fluo-3 and Rhod-2 have been the most valuable dyes for measuring Ca2+. In recent years, AAT Bioquest has introduced the most robust calcium probes: Fluo-8®, Cal-520® and Calbryte™ 520 all of which enable high throughput screening of GPCR and calcium channel drug discovery targets by monitoring calcium flux. FLIPR® and FlexStation® instruments of Molecular Devices, FDSS®/?Cell of Hamamatsu and NOVOstar of BMG Technologies have further accelerated the high throughput measurement of calcium for GPCR and ion channel research.
Fluorescent Single-Wavelength Calcium Indicators
Among visible light-excitable calcium indicators, Fluo-8®, Fluo-4, Fluo-3, Rhod-2 and Rhod-4™ are most commonly used. Fluo-8® indicators are widely used in flow cytometry, confocal laser-scanning microscopy and for high throughput screening of GPCR targets. Fluo-8® is essentially nonfluorescent unless bound to Ca2+ and exhibits a quantum yield of ~0.15 in the presence of saturating Ca2+ and a Kd of 390 nM for Ca2+. Cal-520® is by far the best 488 nm-excitable green fluorescent calcium indicator with a significantly improved signal/background ratio and intracellular retention.
The long-wavelength Rhod-4™, Cal-590™ and Cal-630™ are valuable alternative Ca2+ indicators to the green fluorescent Fluo-8®, Fluo-4 and Fluo-3 for experiments in cells and tissues that have high levels of autofluorescence. Rhod-5N has a lower binding affinity for Ca2+ than any other BAPTA-based indicator (Kd = ~320 µM) and is suitable for Ca2+ measurements from 10 µM to 1 mM. Like the parent Rhod-2 indicator, Rhod-5N is essentially nonfluorescent in the absence of divalent cations and exhibits strong fluorescence enhancement with no spectral shift upon binding Ca2+. All Fluo, Cal and Rhod indicators are available as cell-impermeant potassium salts or as cell-permeant AM esters.