TABLE 1.

Key characteristics of red fluorescent proteins with excitation peak at 580–590 nm.

	Crimson	mCherry	mKate2	FusionRed
Ex peak (nm)	588	587	588	580
Em peak (nm)	617	610	633	608
EC (mM−1cm−1)	77	72	63	95
QY	0.42	0.22	0.4	0.19
Brightness a	32	16	25	18
Photostability (s) b	49	68	58	131
Maturation half-time (min) c	14	15	< 20	130
Maturation efficiency d	50%	44%	49%	24%
pKa	4.2	< 4.5	5.4	4.6
Oligomerization	dimer	monomer	dimer	monomer

^aCalculated as the product of QY at peak excitation and EC in units of mM⁻¹ cm⁻¹.

^bPredicted time for fluorescence to photobleach by 50% under arc-lamp illumination with excitation intensity adjusted to produce 1,000 emission photons per molecule per second.

^cTime for fluorescence to obtain half-maximal value after exposure to oxygen.

^dFunctional chromophore concentration divided by total protein concentration. Functional chromophore is determined using the base-denaturation method as EC measurement. This excludes unfolded and broken-chromophore (backbone cleavage before the first residue of chromophore) components. Total protein is determined by absorbance at 280 nm.