Besides water-soluble elastin conjugate (85113), AnaSpec also offers water-insoluble fluoresceinated elastin. This water-insoluble conjugate can also be used for fluorometric measurement of elastase activity. Product 85103 is insoluble bovine neck ligament elastin that is heavily labeled with FITC such that the conjugate's fluorescence is quenched. Upon digestion by elastase or other proteases, the fluorescence is recovered. Digestion products from the elastin substrate have absorption maxima at ~492 nm and fluorescence emission maxima at ~515 nm. This insoluble elastin derivative is more specific for elastase than 85113.