Assay with Invitrogen's kit. This is an old Thermomyces xylanase prep made to ~10mg/ml a few months ago and stored in the fridge. For assay purposes I diluted it 100x (should have diluted 1000x). Assay was conducted in 100 microliters of 12.5 micrograms/ml substrate for 45' at 37C (pH 6). Assay likely more sensitive at higher temps.
Photographed through Tiffen green 11 and 520nm long pass filters.