Blue fluorescent protein BFP is a monomeric fast maturating and highly photostable protein that is suited for protein labeling in acidic environments due to its high pH stability. BFP has a bright blue fluorescence with excitation/emission maxima at 402 and 457 nm and is a preferred candidate for multi color imaging.
Unlabeled variants and several modifications of sdAbs like biotin, fluorophore or DBCO conjugation are available.
In FluoTag®-Q each fluorophore is coupled to exactly one FluoTag, which in turn binds to its target molecule in a monovalent fashion. The high binding affinity and a coupling efficiency of > 95% guarantees a highly linear relation between the number of target molecules and the intensity of fluorescence. This enables a direct count of the target molecule of interest. The fluorophore is located exceptionally close to the recognized epitope (< 1.5 nm), which is ideal for all microscopy techniques.
In FluoTag®-X two fluorophore molecules are site-specifically coupled to each FluoTag molecule. Therefore, the reagent simultaneously targets up to four fluorophores (in X4 variants) to the protein of interest, which ensures extra-bright 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.