. 2019 Feb 1;24(3):537. doi: 10.3390/molecules24030537

Table 1.

Uses, advantages and drawbacks of different BRET systems.

Name *	Donor	λ_em ^§	Acceptor	λ_em ^§	Substrate	Advantages	Drawbacks	Refs
BRET 1	RLuc/RLuc8	480	eYFP	530	CLZN h	Monitor PPI at endogenous expression levels of protein RLuc8 more stable than RLuc	Sensitive to solvent polarity, serum and pH	[13,14]
BRET 1 ^1.1	RLuc/RLuc8	480	Venus	530	CLZN h	Venus has faster and more efficient maturation compared to YFP Working distance range increased (2.7–8.3 nm) compared to BRET 1 (2.2–6.6 nm)		[13,15]
BRET 1 ²	RLuc	480	eYFP	530	Enduren	Monitoring of PPI several hours in real-time under near-physiological conditions	Requires expensive Enduren	[15,16]
BRET 1 ³	RLuc8	480	mOrange	564	CLZN h	Application for BRET imaging Wide spectral separation Δλ: 84 nm	mOrange: slow maturation processes (t_1/2: 2 h)	[17]
BRET 1 ^3.1	RLuc8	515	mOrange	564	CLZN v	CLZN v increases the spectral overlap between donor emission and acceptor excitation	Low spectral separation Δλ: 50 nm	[18]
BRET 1 ^4.1	RLuc8	515	TagRFP	584	CLZN v		Low spectral separation Δλ: 70 nm	[18]
BRET 1 ⁵	RLuc8.6	535	TagRFP	584	CLZN h	Increased stability and enhanced enzymatic activity of RLuc8.6 compared to RLuc8	Low spectral separation Δλ: 50 nm	[18]
BRET 1 ⁶	RLuc8.6	535	TurboFP	635	CLZN h	High spectral separation Δλ: 100 nm Application for BRET in living animals		[18]
BRET 1 ⁷	Gluc	470	eYFP	530	CLZN h	Gluc smaller and brighter luciferase	Glu activity depends on pH and NaCl concentration Secreted luciferase	[19,20]
BRET 1 ^7.1	hGluc	470	TdTomato	580	CLZN h	Large spectral separation compared to Gluc/eYFP pair Δλ: 110 nm High tolerance toward the solution components (serum) and pH.	TdTomato: slow maturation processes compared to GFP Low stokes shift	[21]
BRET 1 ^7.2	hGluc	470	DsRed	583	CLZN h	Large spectral separation: Δλ: 110	DsRed: slow maturation processes, fluorescent intensity lower compared to GFP	[22]
BRET 2	RLuc	395	GFP2	510	DeepBlueC	Large spectral separation: Δλ 115 for BRET2 vs. 50 for BRET1 ¹	DeepBlue C: weak and short lasting light emission Necessity high expression of BRET partners	[23]
BRET 2	RLuc2	420	GFP2	510	DeepBlueC	Working distance range increased (3.8–11.5 nm) compared to BRET 1 (2.2–6.6 nm)		[13]
BRET 2	RLucM/RLuc8	400	GFP2	510	DeepBlueC	RLuc8 increased stability and even higher quantum yield BRET signal 30 fold higher than RLuc/GFP2 pair Application for BRET in single live cells and living animals		[24]
BRET 3	FLuc	565	DsRed	583	D luciferin	DsRed: high photostability and resistance to pH; Application for in vivo imaging	Overlap of donor/acceptor emission Low signal/noise	[17,22]
BRET 3	FLuc	565	Cy3/Cy3.5	570/596	D luciferin		Overlap of donor/acceptor emission Low signal/noise	[25]
NanoBRET	Nluc	462	haloTag	618	Furimazine	NanoLuc is 100 fold brighter than RLuc. Furimazine permits longer observation (2 h compared to 25 min with coelenterazine)	Not red shifted version available Requires expensive Furimazine	[26]
NanoBRET	Nluc	462	Venus DsRed	535	Furimazine	Improved sensitivity and dynamic range Used as biosensor Single cell BRET imaging	Not red shifted version available Requires expensive Furimazine	[26]
QD-BRET ¹	RLuc	480	Qdot	620	CLZN h	Used as biosensor Larger stokes shift Resistance to photobeaching Strong fluorescence		[27]
QD-BRET ²	RLuc8	480	Qdot	655	CLZN h	Real time in vivo imaging	Size of Qdot	[28,29]
QD-BRET ³	FLuc	565	Qdot	613/628 675	CLZN h	Working distance range increased	Problem for Coupling to proteins; cellular toxicity	[30,31]

* Authors gave name for each system described. However, as no standard nomenclature has ever been established, these names are not absolute or exclusive, for reference only. ^§ Peak wavelength in nm.