The Oyster®-550-Streptavidin is a bright, orange fluorescent conjugate, which is excitated best by the 546 nm line of a mercury-arc lamp or the 543 nm of a He-Ne laser. Streptavidin is a non-glycosylated biotin-binding protein with a iso-electric point near pH 7.0. Oyster®-550 is spectrally similar to Cy3 ™, Tetramethylrhodamine (TRITC) or Alexa Fluor ® 555.