Self-assembly of Nematic Liquid Crystals in Drying Drops of Lysozyme Protein Solution

In the recent years, an active area of research involves liquid crystals (LCs), e.g. 5CB (4-Cyano-4'-pentylbiphenyl) for sensing biological and chemical analytes. Another active area studies drying protein drops resulting in emergent patterns at the final dried state. In this presentation, these two areas are bridged by adding 5CB, with initial protein solution of lysozyme and de-ionized water. The investigation is done using bright-field and cross-polarizing microscopy, analyzed using ImageJ and Fiji and quantified using statistical tests. It is observed that the crack patterns in the final dried state of the protein is influenced by the presence of small amounts of 5CB. Since the protein lysozyme is not birefringent, cross-polarizing microscopy closely monitors the distribution of the LC, while the bright-field microscopy probes the crack patterns that emerge. The time evolution of the drying dynamics of the drops with and without 5CB are monitored. It is concluded that partial phase separation of LC makes some LC remains mixed and some dispersed into the domains formed by protein cracks. This work demonstrates the utility of using a bulk thermotropic LC as a probe material in a protein solution, revealing new information on the protein self-assembly during the drying process.