Table 2. Exogenous probes used in VCF studies
ProbeUsage notesReferences
ToxinsToxins often have highly specific binding sites that remain static during channel gating and therefore can serve as useful reference points for FRET studies. However, not all channels have highly specific toxins, and toxin binding can influence channel gating in some instances.Posson et al., 2005; Kubota et al., 2017
DPAHydrophobic, anionic dye that rapidly localizes to the outer membrane leaflet at depolarized potentials and inner leaflet at hyperpolarized potentials. Often used in FRET studies probing distance changes relative to the membrane; however, it is known to modify channel gating for many ligand-gated ion channels.Chanda et al., 2005; Taraska and Zagotta, 2007
OxonolVoltage-dependent, anionic dye that translocates between leaflets depending on membrane potential, similar to DPA. However, rate of translocation is on the order of hundreds of milliseconds, 350-fold slower than that of DPA.Chanda et al., 2005
C18-NTALipid mimetic with metal chelating tag at head group that can be used to label membrane with transition metals for probing distance changes relative to membrane.Aman et al., 2016
Potassium iodideCollisional quencher that is often used to probe changes in solvent accessibility during channel gating.Mannuzzu et al., 1996; Zheng and Zagotta, 2000

NTA, nitrilotriacetic acid.