The energy output of a FOTODYNE transilluminator equipped with 312 nm UV bulbs is approximately 7000 µW/cm2. NOTE: The optimal energy for crosslinking has been reported to be approximately 1600 Joules per square meter of wet membrane and 160 Joules per square meter of dry membrane. There are many variables in the blotting and crosslinking procedure that may influence the length of time required to expose a membrane to UV light for optimal crosslinking. These may include: brand and type of membrane, size and type of nucleic acid, wetness of membrane, age and condition of UV bulbs, transfer buffer composition, etc. Therefore the best crosslinking conditions should always be determined empirically for the exact experimental system being used.