The results, summarized in Table 2, indicate that (1) the structure of nonaggregated protein is not compromised, (2) the protein aggregation effect by irradiation of the USP laser depends on the type of proteins; apparently, BSA is much more stable than mAb04 and exhibits very little aggregation upon USP laser irradiation, (3) the aggregation effect depends on protein concentration, with higher concentration tending to aggregate more, and (4) mixing the stable protein (BSA) with a less stable one (mAb04) does not help stabilize the less stable protein. This information further supports our proposed model that the USP laser first unfolds the proteins by disrupting their hydrogen bonds/hydrophobic contacts. The unfolded proteins then aggregate before the rapid reformation of these weak bonds. The higher protein concentration means they are closer to each other and as a result have a higher chance of aggregating. We note that under our experimental conditions, the proteins were completely dissolved in their buffer solutions, as evidenced by the almost 99% of monomer (nonaggregated proteins) in the solutions. In other words, our interpretations of protein aggregation by USP laser irradiation were not affected by the problem of solubility of the proteins in the buffer solution. In addition, the two proteins, BSA and mAb04, were chosen for the DLS experiments because neither of them absorb near 425 nm. As a matter of fact, we measured the temperature of the solutions during the laser irradiation experiments with a thermal couple immersed into the solution. The temperature of the solution rose no more than 2°C. Since the denature temperature of both proteins is around 60°C, our results cannot be due to the heating effects.