Table 1.

Measurement of glutathione redox state in the mammalian ER. Since the redox potential of glutathione buffers depends on the [GSH]²/GSSG term, they are dependent on absolute concentration (see the Text). For the purposes of comparison, these values assume a total glutathione concentration (GSH + 2 GSSG) of 10 mM. At a ratio of GSH:GSSG of 3:1 the redox potential would be -186 mV; lower aggregate concentrations of 7.5 and 5 mM glutathione would yield somewhat more positive redox potentials of -182 mV and -177 mV respectively. We have arbitrarily used 10 mM total glutathione to present a comparison with the redox potentials reported for the fluorescent probes entries 5-7.

Entry	Biological Sample	Method	GSH:GSSG	Reported redox potential	Adjusted Value	Year/Reference
1	Murine hybridoma CRL1606 cells	ER targeted peptide	1:1 to 3:1	-170 to 185 mV (8 mM)	-164 to -186 mV	1992/[66]
2	Rat liver microsomes	Microsomal Isolation	3:1 to 4:1	NR	-186 to -192 mV	2004/[67]
3	Rat liver microsomes	Microsomal Isolation	4.7:1 to 5.5:1	NR	-194 to -197 mV	2008/[68]
4	HeLa cells	sCGrx1pER probe NEM soaking	<7:1	NR	>-201	2013/[54]
5	Human fibroblast cells (HT1080)	roGFP1iL	NR	-231 mV	NA	2011/[72]
6	CHO cells	CY_RL7 fluorescent probe	NR	-118 mV	NA	2012/[75]
7	pancreatic acinar cells (AR42j)	roGFP1iE	NR	-236 mV	NA	2013/[74]
8	HeLa cells	Grx1_roGFP1iE	NR	-208 mV	NA	2013/[73]