Fig. 2
Binding isotherm of the Glu[−] biosensor in either MOPS (20 mM, pH 7.3) (a) with CGXII medium (2.5% v/v) and (b) without addition of medium without shaking. The FRET-ratio (IA/ID) was calculated from the emissions of the donor mTurquoise2 at 485 nm (± 20 nm) and acceptor Venus at 528 nm (± 20 nm) after excitation of the donor at 428 nm (± 9 nm) according to Eq. (1). Between measurements the sensor was stored protected from light at 4 °C. The curves (dotted) were fitted to the data according to Eq. (2)