4-Nitrophenyl phosphate
4-Nitrophenyl phosphate (p-Nitrophenyl phosphate) is widely used as a small molecule phosphotyrosine-like substrate in activity assays for protein tyrosine phosphatases.4-Nitrophenyl phosphate is a colorless substrate that upon hydrolysis is converted to a yellow 4-nitrophenolate ion that can be monitored by absorbance at 405 nm.