Table 2.
Examples of commonly used tools and methods to study zinc.
| Type | Method | General description |
|---|---|---|
| Manipulation of zinc availability | Membrane-impermeable chelators | Compounds with high zinc affinity that are unable to cross the lipid bilayer of cells to manipulate zinc availability in media. One example is zinc-diethylenetriamine pentaacetate (Zn-DTPA) that has a high affinity for zinc but also forms complexes with other heavy metals such as actinides |
| Membrane-permeable chelators | Compounds with zinc affinity that cross the plasma membrane to enter cells to sequester intracellular zinc. The most commonly used in reproductive biology is TPEN N,N,N′,N′-tetrakis(2-pyridylmethyl)ethane-1,2-diamine, which has a high affinity for zinc but also binds other transition metal ions such as copper and iron | |
| Zinc ionophore | Increases intracellular zinc uptake. A potent zinc ionophore is zinc pyrithione, a derivative of pyrithione that is also known to mediate influx of other ions such as copper, is used in vitro | |
| Dietary ZD | Used in animal models to assess in vivo effects of ZD. Zinc-deficient diets typically consist of <3 mg zinc/kg in the diet compared to control diets of >= 29 mg zinc/kg | |
| Fluorescence probing (reviewed in [236, 237] | Small molecule indicators | Zinc-selective fluorophores that range in sensitivity, typically have cell permeable and impermeable versions, and are easy to use in cell culture. However, these probes typically have similar excitation and emission spectra, and assumptions that these indicators only bind labile zinc appear to be invalid. Examples used commonly in reproductive biology include FluoZin-3 and Zinquin |
| Peptide-based zinc indicators | Exploits naturally derived zinc-binding peptides with fluorescent sensors. These probes have a greater range of excitation and emission wavelengths and can target specific subcellular compartments; however, they are more difficult to use and have a smaller dynamic range compared to small molecule indicators. Includes single protein-based zinc fluorophores, Forster resonance energy transfer (FRET)- and bioluminescence resonance energy transfer (BRET)-based probes. Examples include ZnGreen, Zap, and BLZinCh | |
| Total elemental imaging and mapping (reviewed in [236]) | X-ray fluorescence microscopy | High-resolution technique that can image total (free and bound) zinc localization and quantify zinc abundance by the atom. Includes synchrotron X-ray fluorescence, X-ray absorption spectroscopy, and energy-dispersive spectroscopy |
| Mass-spectrometry-based imaging | Employs ionization methods to detect particles by their mass-to-charge ratio. Examples include laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) and secondary ion mass spectrometry (SIMS) |