Pyrene is a UV excitable fluorescent dye that has unqiue fluorescent properties. Pyrene has exceptionally long excited-state lifetimes (>100 nanoseconds). This property make it useful for time-resolved fluorescence immunoassays. Pyrene dyes also form excited-state dimers (excimers) with fluorescence emission at llonger wavelengths than its monomers. This property has been used for protein interaction study. Nanocs provides a number of pyrene PEG derivatives that can be used for protein, antibody and other biomolecule labeling. We also offer lipid/phospholipid PEG pyrene derivatives that can be used for cell membrane study.