A heterobifunctional cross-linking reagent containing a sulfhydryl-specific group and a photo-active group. Typically, coupled initially by thioether to molecule containing free sulfhydryl buffered at pH 6.8 (6.5-7.0). Second bonding occurs during UV irradiation (250 nm) via diradical excited state. Benzophenones demonstrate greater specificity for C-H insertion and are more stable in water than analogous reagents. In general they are more efficient in attachment because they may be repeatedly irradiated; however, a more intense irradiation may be required. The benzophenone is not sensitive to
