Basic properties of Fluo-4 and GCaMP3
| Fluo-4 | GCaMP3 (Looger laboratory) | GCaMP3 (Campbell laboratory) | |
| Peak excitation wavelength (nm) | 494 | 497 | 496 |
| Peak emission wavelength (nm) | 516 | 514 | 513 |
| Ca2+ affinity (nM) | ∼350 | ∼660 | ∼542 |
| εmax Ca2+ bound (cm−1 M−1) | 88,000 | 37,000 | 50,000 |
| Φ Ca2+ bound | 0.14 | 0.65 | 0.44 |
| Fmax/Fmin | ∼100 | ∼12 | ∼12 |
| Reference | Haugland and Johnson, 1999 | Tian et al., 2009; Akerboom et al., 2012 | Zhao et al., 2011 |
| Fluo-4 | GCaMP3 (Looger laboratory) | GCaMP3 (Campbell laboratory) | |
| Peak excitation wavelength (nm) | 494 | 497 | 496 |
| Peak emission wavelength (nm) | 516 | 514 | 513 |
| Ca2+ affinity (nM) | ∼350 | ∼660 | ∼542 |
| εmax Ca2+ bound (cm−1 M−1) | 88,000 | 37,000 | 50,000 |
| Φ Ca2+ bound | 0.14 | 0.65 | 0.44 |
| Fmax/Fmin | ∼100 | ∼12 | ∼12 |
| Reference | Haugland and Johnson, 1999 | Tian et al., 2009; Akerboom et al., 2012 | Zhao et al., 2011 |
Two available values for key parameters from the Looger and Campbell laboratories are listed for GCaMP3. The Fmax/Fmin ratio is the ratio of emission fluorescence intensities in the presence (Fmax) and absence of saturating Ca2+ (Fmin). Thus, both indicators increase in emission intensity when Ca2+ is bound. The peak excitation and emission wavelengths are for the Ca2+-bound indicators. Further information is available in the indicated references. Ca2+ affinity indicates the dissociation constant (Kd). The εmax Ca2+ bound (cm−1 M−1) for Fluo-4 is quoted from the Invitrogen Molecular Probes website (http://tools.invitrogen.com/content/sfs/manuals/mp01240.pdf). The values were measured with the indicators in solution at a pH of ∼7.2. εmax, peak extinction coefficient; Φ, quantum yield.