mScarlet-i is a basic, very bright red fluorescent protein, derived from a synthetic construct (1). It is reported to be a rapidly-maturing, constitutively fluorescent monomer with moderate acid sensitivity. It is a useful acceptor in Foerster resonance energy transfer (FRET) based imaging techniques (2).
Unlabeled variants and several modifications of sdAbs like biotin, fluorophore or DBCO conjugation are available.
In FluoTag®-X2 two fluorophore molecules are site-specifically coupled to each FluoTag molecule. Therefore, the reagent simultaneously targets two fluorophores to the protein of interest, which ensures up to two-fold („2X“)-brighter signals. Owing to the small size of the FluoTags, the distance between the target epitope and each fluorophore is ~ 3 nm.
In comparison to detection systems using conventional antibodies, FluoTag-X can thus improve the localization accuracy by 10-15 nm. Both features - superior brightness and precise fluorophore placement - render the FluoTag-X products excellent tools for all microscopy techniques.