In nature, proteins are also probable to degrade under the sunlight, and the reason is that the energy of light excites the solvent (almost water) and initially generate radicals, which afterward propagate and attack protein to break it down until termination.
Ionizing radiation causes the radiolysis of water is, the major process is shown below. (Figure 7)
Figure 7. The radiolysis process of water.
Though the real mechanism that radicals attack to protein is quite complex, we can simply indicate the rate of protein been attacked by an unknown power, n, of the total concentration of radicals. Then we derived the rate formula as differential equations.
Where [radical ]: the total concentation of radicals, [P ]: the concentation of Pantide, Gγ : the dose rate of absorbing γ-ray (radiation energy absorption rate per mass, for water, 1.42 Gy/s) , Aγ : the number of radicals created per energy (for water, 0.045 μmol/J) , I : the intensity of UVB from sunlight measured by UV Sensor (UVM30A), RT : the rate constant of radicals termination, which is equal to 2.365×10-7 mol-1 s-1 , KUV : the rate const ant of UV radiolytic oxidation to protiens, which is set to 44 mol-1 s-1 at the beginning 
We then used software MATLAB to simulate the degradation rate by UV radiolytic oxidation on the intensity of UVB from sunlight. The results showed that the degradation rate increases as rising intensity whatever n is, and eventually it tends to be fully degraded. (Figure 8)
Figure 8. The simulation of degradation rate by UV radiolytic oxidation on the intensity of UVB from sunlight.
ii. Experimental proof
We applied the four kinds of native protein solutions to the UVB light from UV transilluminator (302 nm, 50 mW/m2 ) in the period of 2 hours, where the environment temperature was 36.8℃ in average. The results showed the six proteins degraded under UVB light treatment and the tendency of the reduction of proteins corresponded to our model. (Figure 9)
Figure 9. The degradation rate of four proteins by UV radiolytic oxidation as time goes on.
The degradation rates are obviously different between the protein with and without fusing to lectin. The possible reason we concerned was the difference in amino length; the longer protein has a relatively high probability to be attacked.
To determine the relation between the UVB light intensity and the degradation, we fit the result from experiments to our model. We calculated the parameter n in formula (4) must be equal to 0.78. The rate constant KUV for Hv1a, Sf1a, OAIP 7.8 15.7and Hv1a-lectin are 2.4, 7.8, 15.7 and 90.3.
We also applied native Hv1a-lectin with another UV transilluminator (286 nm, 36.4 mW/m2 ), and compared with the prediction from our model. (Figure 10)
Figure 10. The model prediction compared with the experiment data.
The figure showed our model is on the right way, but to accomplish our purpose; we still need more experiment data to correct the parameters.