single-molecule localization microscopy

HM Janelia Fluor 526, SE (HM-JF526 NHS) is a derivative of hydroxymethyl JF526 (HM-JF526). SMLM (single-molecule localization microscopy) imaging in standard phosphate-buffered saline (pH 7.4) revealed that the HM-JF526 label showed spontaneous blinking behavior throughout the imaging session and did not require short-wavelength activation light . Janelia Fluor fluorescent dyes can be chemically conjugated to the specific HaloTag substrate (a chloroalkane ligand) to form a fluorescent ligand, rather than binding directly to the HaloTag protein itself. Janelia Fluor products are licensed under U.S. Pat. Nos. 9,933,417, 10,018,624 and 10,161,932 and other patents from Howard Hughes Medical Institute.

JF635-HTL is a Fluorescent dye for spatiotemporally controlled live cell imaging and single-molecule localization microscopy SMLM. Its detection mechanism depends on the conformational change of a photoswitchable HaloTag psHaloTag, which integrates the light-responsive AsLOV2 domain: in the dark state, the folded Jα helix of AsLOV2 maintains the dye in a predominantly closed, non-fluorescent form; upon 450 nm illumination, a metastable photo-adduct forms between a cysteine side chain and the FMN cofactor of AsLOV2, causing undocking and unfolding of the Jα helix, which propagates a conformational change to the HaloTag near the dye binding site, shifting the dye's equilibrium to the open, fluorescent form; this process is fully reversible in the dark as the Jα helix refolds spontaneously, returning the dye to the closed, non-fluorescent state. For psHaloTag1a labeled with JF635-HTL, the excitation/emission wavelengths for the ON state are Ex/Em = 642/655 nm, while for psHaloTag1b labeled with JF635-HTL, the wavelengths are Ex/Em = 639/655 nm; when bound to wild-type HaloTag, the wavelengths are Ex/Em = 640/656 nm .