Table 1.

Fluorescence response properties of VSFP2.1 variants. Steady state spectrally-resolved maximal changes in fluorescence acquired from voltage-clamped PC12 cells. The ΔR/R values represent the average of 14–37 measurements from hyperpolarized (−100 mV) to depolarized (+40 mV) membrane potential from five representative cells (data are from Mutoh et al., 2009).

	ΔR/R (%)	τon (to +60 mV, ms)	τoff (from +60 mV for 500 ms) (ms)	Steady state V1/2 (mV)
VSFP2.3	13.3 ± 3.4	1.9 ± 0.9 and 24.5 ± 0.3	78.4 ± 0.5	−49.5 ± 1.1
VSFP2.4	12.4 ± 1.0	2.3 ± 0.2 and 24.2 ± 0.2	72.2 ± 0.4	−54.2 ± 2.0
Mermaid	12.9 ± 4.8	3.2 ± 0.2 and 24.8 ± 0.3	76.4 ± 0.4	−43.6 ± 1.0