Presentation Information

[24a-P01-11]Optical Trapping and Single Droplet Formation of Lysozyme at Solution Surface

〇(M1)Yi-Sian Chien1, Po-Wei Yi1, Ching-Yang Lin1, Shuichi Toyouchi1, Henryk Witek1, Keisuke Yuzu2, Eri Chatani2, Hiroshi Masuhara1 (1.Nat'l Yang Ming Chiao Tung Univ., Taiwan, 2.Kobe Univ., Japan)


Optical Trapping,Single droplet formation

Optical trapping is a method of grabbing particles with sizes ranging from nanometers to micrometers by using a tightly focused laser beam without any mechanical contact. Our group has demonstrated a single disk-like assembly formation of lysozyme at air/solution interface by focusing a 1064 nm trapping laser.1 The assembly expands much larger than the focal spot during laser irradiation and shrinks down within few seconds upon turning off the laser. We call the phenomenon as optically evolved assembling.2
Liquid-liquid phase separation (LLPS) has been considered a critical phenomenon in nature,3 while never observed for lysozyme by using optical trapping technique. In this work, we study optical trapping and assembling of lysozyme with sodium chloride (NaCl) at the air/solution interface and successfully demonstrate single protein droplet formation at the trapping focus due to LLPS. We examine the salt effect by varying the NaCl concentration (1 to 5 wt%) for D2O solution of lysozyme (375 to 40 mg/mL). In the case of 375 and 300 mg/mL, only single disk-like assembly was formed with and without NaCl. In the case of 200 and 100 mg/mL of lysozyme, the assembly was identified only when NaCl was added. On the other hand, a new assembling behavior was induced for 40 mg/mL lysozyme with 4 wt% NaCl. The formation of a single lysozyme droplet was reversible when its size is small (Fig. 1a), while it became irreversible when the size of the droplet was large enough (Fig. 1b). We consider the single droplet is formed via LLPS and are now investigating its dynamics and mechanism.