Table 1. Theoretical BRET Values for NanoLuciferase Donor and Fluorescent Protein Acceptor Pairs.

Fluorescent Protein	Extinction Coefficient (M−1cm−1) ε	Fluorescence Quantum Yield Φ	Brightness (ε•Φ)	Spectral Overlap (x1014)	Theoretical Förster Radius (Å)	Acceptor Emission Maximum (nm)	Peak Emission Shift (nm)*	Background Nanoluc Signal**
mCherry	72000	0.22	15840	4.19	37.1	610	160	0.06
mPlum	41000	0.01	410	2.4	33.8	649	199	0.06
mStrawberry	90000	0.29	26100	6.64	40.1	596	146	0.11
mTangerine	38000	0.3	11400	2.9	34.9	585	135	0.14
mOrange2	58000	0.6	34800	5.39	38.7	565	115	0.34
mKO	51600	0.6	30960	4.68	37.8	559	109	0.39
mBanana	6000	0.7	4200	0.73	27.7	553	103	0.43
Citrine (YFP)	77000	0.76	58520	7.66	41.0	529	79	1.21
Emerald GFP	57500	0.68	39100	13.7	45.2	509	59	1.70
mHoneydew	17000	0.12	2040	5.47	38.8	562	112	2.11
Cerulean (CFP)	43000	0.62	26660	9.86	42.8	475	25	4.54

(*the peak emission shift was calculated by subtracting the Nluc emission maximum [450 nm] from the acceptor protein emission maximum; **the theoretical background BRET ratio was calculated by taking the ratio of light emitted by Nluc alone at the acceptor emission maxima divided by the measured donor wavelength [410 nm]).