Spectroscopic Analysis of Concentration Dynamics and Crystallization of Hen Egg-White Lysozyme under Optical Trapping Conditions

This study explores the optical trapping of hen egg-white lysozyme (HEWL) using a focused laser beam. It also investigates the HEWL concentration dynamics leading to HEWL crystallization, which is analyzed by using fluorescence spectroscopy. The HEWL clusters in a buffer solution are trapped at the focal point by optical trapping, forming an aggregate. Crystallization does not occur during laser irradiation, while cessation of laser irradiation triggers the crystallization of HEWL, and the resulting HEWL crystals are densely distributed at the focal point. Real-time monitoring of the relative fluorescence intensity allows for precise control of the HEWL concentration and identification of the optimal conditions for crystal formation. The fluorescence study reveals the formation of a highly concentrated domain (HCD) at and around the focal point and suggests that the slow diffusion of HEWL clusters from the HCD leads to a prolonged high concentration that triggers the resulting crystallization. The results reveal the multifaceted processes of optical trapping, protein concentration dynamics, HCD formation, and HEWL crystallization, which have potential applications in controlled crystallization methods and provide insights into biophysics and materials science.