Table 1 Characteristics of common green-emitting FPs, StayGold and its variants

	λab^a/λem^b (nm)	ε^c (10³ M⁻¹cm⁻¹)		QY_f^d	Brightness		Photostability t_1/2 (s)^g	Monomericity/dispersibility (% normal-looking cells)
		λab	483		Mol^e	Cell^f		OSER	Fluoppi
		λab	483		Mol^e	Cell^f		CytERM-FP	PB1-FP	FP-PB1
EGFP	488/509	51	51	0.71	36	0.22	227 ± 9	83.4	65.2	NT
mEGFP	488/509	56.5	56.5	0.70	40	NT	203 ± 7	89.8	69.0	NT
mClover3	505/518	99	52	0.84	83	NT	40 ± 3	87.0	97.9	NT
mNeonGreen	505/518	112	64	0.87	97	0.32	162 ± 6	74.2	48.6	NT
mGreenLantern	501/515	117	76	0.74	87	0.51	6.5 ± 0.2	83.1	100	NT
StayGold	496/505	159	105	0.93	148	1.00	5,190 ± 138	69.0	46.4	20.7
tdStayGold	496/504	162	108	0.90	146	NT	4,198 ± 106	95.0	71.8	64.6
tdoxStayGold	496/504	NT	NT	NT	NT	NT	NT	58.3	75.5	64.5
td5StayGold	496/504	155	103.4	0.91	141	2.09	4,491 ± 201	91.5	96.4	90.1
td5oxStayGold	496/506	156	102.6	0.93	145	2.71	3,753 ± 340	88.5	94.1	60.1
td8oxStayGold	496/506	157	103	0.93	146	2.73	4,958 ± 137	93.4	100	97.5
td8ox2StayGold	496/506	159	105	0.93	148	2.77	4,495 ± 177	91.9	100	93.9
QC2-6	496/504	NT	NT	NT	NT	NT	NT	85.7	55.6	NT
QC2-6 FIQ (mStayGold)	499/510	164	100	0.83	136	0.95	4,898 ± 199	92.3	100	100
QC2-6(PT) (mStayGold2)	499/509	175	110	0.79	138	0.71	2,753 ± 172	82.6	100	98.2

^aAbsorbance maximum.
^bEmission maximum.
^cAbsolute extinction coefficient at λab (left) and 483 nm (right). The measurement was based on the fact that after alkali denaturation of these FPs, the chromophore, containing a dehydrotyrosine residue conjugated to the imidazolone group, absorbs light maximally at 447 nm with a molar extinction coefficient of 44,000 M⁻¹ cm⁻¹ (ref. ⁴⁵). See Supplementary Fig. 5.
^dFluorescence quantum yield measured using an absolute photoluminescence quantum yield spectrometer.
^eProduct of ε (λab) and QY_f. This value reflects the molecular brightness of an FP⁴⁶.
^fCellular brightness calculated from data shown in Fig. 3b. The fluorescence from each green-emitting FP (with excitation at 483 nm) was corrected for mCherry fluorescence and spectral throughput (Supplementary Fig. 7) and then normalized to that of StayGold. Equimolar coexpression of a green-emitting FP and mCherry using the bicistronic expression system¹².
^gTime in seconds to reduce the emission rate from 1,000 to 500 photons s⁻¹ per molecule under WF illumination. Live HeLa cells expressing H2B-FP fusions were used (Fig. 2). Values are mean ± s.d. (n = 3 independent experiments). All values were measured by us (underlined, in a previous study¹; otherwise, in this study). NT, not tested. QC2-6 FIQ and QC2-6(PT) were designated as mStayGold (mSG) and mStayGold2 (mSG2), respectively.

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