Sterile 10 mM Histidine, pH 5.5 buffer is a versatile solution with significant applications in protein purification, vaccine preparation, drug development, cell culture, and electrophoresis. Histidine, an amino acid, provides excellent buffering capacity. Its sterility and specific pH conditions make it ideal for experiments requiring precise environmental control. Histidine in this buffer can derive photosensitizers, which increase significantly upon light exposure. These histidine-derived photosensitizers act as primary mediators in the photooxidation of tryptophan.