Table 1.

In vitro characterization of pH-sensitive FPs

Protein	pKa	nH	Fluorescence fold change (pH 5.5–7.5)	Excitation peak at pH 7.2	Emission peak at pH 7.2
				nm	nm
SE-pHluorin	7.2	1.90	50	495	512
mNectarine	6.9	0.78a	6	558	578
pHTomato	7.8	0.51a	3	562	578
mOrange	6.5	0.77	5	548	562
pHoran1	6.7	0.87	10	547	564
pHoran2	7.0	0.89	12	549	563
pHoran3	7.4	0.87	15	551	566
pHoran4	7.5	0.92	17	547	561
mCherry-TYG	7.8	0.73a	5	546	568
mApple	6.6	0.68	4	568	592
A-9	7.4	0.73	12	576	596
A-17	7.2	0.87	11	576	596
A-47	7.1	0.83	10	570	592
pHuji	7.7	1.10	22	566	598

^aBiphasic titration curve. To obtain the apparent n_H, the whole titration curve was fit with a monophasic function.