Presentation Information

[24a-P01-8]Optical Trapping Formation and Lift-Up of Lysozyme Assembly at Solution Surface

〇(M1)Chia-Hong Su1, Po-Wei Yi1, Chih-Hao Huang1, Mu-En Li1, Hiroshi Masuhara1 (1.Nat'l Yang Ming Chiao Tung Univ.,Taiwan)


Cooperative optical trapping,Surface deformation,Lysozyme protein assembly

Optical trapping is a novel technique for controlling particles or molecules from nanoscale to microscale. Our group has reported protein assembly along solution surface, which grows larger than the laser focal size, by employing polystyrene microparticles (PS MPs) to depict its morphology1. In this work, we report a new phenomenon in super-concentration lysozyme protein solution. Initially, lysozyme protein is well dispersed in D2O solution and pended for 1 hour before switching on the trapping laser. During the pending time, larger protein clusters are formed near the surface, suppressing their diffusion, which is revealed by tracking analysis of cooperatively trapped PS MPs. Upon turning on the trapping laser, optical force is exerted onto the protein clusters, and the prepared assembly show the surface deformation with high optical force. The lift-up of the protein assembly is confirmed, suggesting that scattering force is larger than gradient force and surface tension force.
In Figure 1a, all PS MPs of 3 μm diameter are well dispersed at the solution surface after pending for 1 hour, which is considered due to their buoyance. Upon switching on the trapping laser, the brightness of PS MPs gives large difference between the central and outer areas, which indicates that they are not at the same height in the transmission image. Moreover, PS MPs near the laser focus is brightest, implying that the solution surface is higher than before trapping. The results mean that optical force strongly pushes up the PS MPs, resulting in the surface deformation. Transmission images of the protein solution with no pending time are given in Figure 1b. A linear stick-like assembly is formed, following the growth of the protein assembly edge, which is consistent with our previous report1. The present assembling and the following surface deformation offer a new viewpoint for understanding optical trapping at solution surface2.