FX technology for improves postfixation and ExM anchoring
Due to the small size, limited surface, and preferential low pKI of sdAbs, it is often hard to modify or crosslink nanobodies using amine-reactive chemistry. This may pose limitations, for example, in fixation after staining (post-fixation) or chemical anchoring into hydrogels as required for expansion microscopy (ExM).
Some of our sdAbs are therefore equipped by default with fixation (FX) cassettes. These proprietary short amino acid stretches introduce multiple primary amines. Their positive charges are fully compensated to ensure a neutral net charge of each FX cassette. By increasing the number of accessible primary amines on our sdAbs, FX cassettes significantly improve the post-fixation properties of sdAbs. This may be an important feature once the intended experiment takes a long time. This may, for example, be the case during single-molecule localization techniques like STORM and DNA-PAINT microscopy, in which samples may be in flow chambers for several hours.