Effect of ultraviolet irradiation on susceptibility of serum albumins to trypsin

Ultraviolet irradiation converts bovine serum albumin (BSA) and rabbit serum albumin (RS A) into forms much more rapidly hydrolysed by trypsin than the original proteins. The radiation energy (at 2537Å) required to be absorbed by each mg of a protein to convert half of it into a form susceptible to trypsin (E50%) is about 0.32 J for BSA and 0.62 J for RSA. The average E50% for inactivation of enzymes and antibodies is 0.7 J so the two processes may depend on similar alterations in irradiated protein molecules. The alteration can be considered as denaturation, with protein molecules becoming at least partially unfolded and making the sites susceptible to the attack by trypsin more easily accessible to the enzyme.