The aggregation of a beta-crystallin water solution exposed to XeCl laser radiation demonstrates the dependence of scattering-exposure curve (scattering versus exposure) on laser intensity. The main features of this dependence can be understood by the relaxation of a partly denaturated state of a protein within some finite relaxation time. These photoactivated states originate from the absorption of UV photons. Two partly denaturated (photoactivated) monomers, as well as other aggregates, can aggregate, giving rise to sharply increasing probe light scattering after some lag time of irradiation.