Comparison List


YPet is a basic (constitutively fluorescent) yellow fluorescent protein published in 2005, derived from Aequorea victoria. It has moderate acid sensitivity.
Oligomerization Organism Molecular Weight Cofactor
Weak dimer Aequorea victoria 26.9 kDa -



Ex λ Em λ EC (M-1 cm-1) QY Brightness pKa Maturation (min) Lifetime (ns)
517 530 104,000 0.77 80.08 5.63    

YPet OSER Measurements

% Normal Cells OSER/NE ratio Cell Type Reference
62.5 ± 5.2 (10000 cells) - HeLa Cranfill et al. (2016)


t1/2 (s) Power Light Mode In Cell Fusion ˚C Reference
30.3 20.0 (mW/mm2) LED Widefield Saccharomyces cerevisiae 24.0 Lee et al. (2020)
58.0 20.0 (mW/mm2) LED Widefield HEK239A 24.0 Lee et al. (2020)

YPet Sequence

YPet was derived from Venus with the following mutations: I47L/L68V/S208F/V224L/L231E/D234N
amino acid numbers relative to avGFP. show relative to Venus



YFP3 possessed six mutations that resulted in an RRC almost fivefold greater than that of the parental pair. YFP3 also conferred a roughly threefold improvement in FRET relative to the fast-maturing Venus YFP. In an attempt to further enhance YFP3 brightness, the Venus mutations were combined with those of YFP3 to yield YFP for energy transfer (YPet). Though YFP3 exhibited slower folding relative to Venus, combining YFP3 and Venus mutations resulted in intermediate folding kinetics.

Nguyen & Daugherty (2005)

Nguyen and Daugherty (2005) reported the development of an improved FRET pair, YPet & CyPet, which had a sevenfold enhancement of the FRET signal. However, we discovered that most of the signal enhancement was due to enhanced dimerization of YPet to CyPet within the tethered construct, and was substantially reduced when we incorporated the monomerizing mutation previously developed to prevent the weak dimerization of GFP (Zacharias et al. 2002).

Ohashi et al. (2007)

Primary Reference

Evolutionary optimization of fluorescent proteins for intracellular FRET

Nguyen Aw, Daugherty Ps

(2005). Nature Biotechnology, 23(3) , 355-360. doi: 10.1038/nbt1066. Article   Pubmed

Additional References

  1. Versatile phenotype-activated cell sorting

    Lee J, Liu Z, Suzuki Ph, Ahrens Jf, Lai S, Lu X, Guan S, St-Pierre F

    (2020). Science Advances, 6(43) , eabb7438. doi: 10.1126/sciadv.abb7438. Article   Pubmed

  2. Advances in fluorescent protein technology

    Shaner Nc, Patterson Gh, Davidson Mw

    (2007). Journal of Cell Science, 120(24) , 4247-4260. doi: 10.1242/jcs.005801. Article   Pubmed

External Resources

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