An Air-Supported Liquid Crystal System for Real-Time and Label-Free Characterization of Phospholipases and Their Inhibitors

A new air-supported liquid crystal (LC) system for analyzing interfacial phenomena that occur based on the molecular interaction between LCs and adsorbed molecules of interest at the aqueous/LC interface is reported. Compared with existing LC-based detection systems, the miniature system reported here requires less sample and involves simpler preparation. Using this system, the enzymatic hydrolysis of various phospholipases such as phospholipase A(2) (PLA(2)), phospholipase C (PLC) and phospholipase D (PLD) are characterized. The hydrolysis of phospholipid monolayers self-assembled at aqueous/LC interface induces an orientational response from the LCs. As a result, an optical signal that reflects the spatial:and temporal distribution of phospholipids during the enzymatic reaction can be generated in a real-time manner. When well-known phospholipase inhibitors are introduced together with respective phospholipases, no orientational response of LCs is observed. In the case of inhibitors MJ33 and compound 48/80, cross-inhibitions among phospholipases are also observed. This work demonstrates that the air-supported LC system provides a facile label-free assay for characterizing phospholipase activities and for screening enzyme inhibitors. It could potentially be useful for different high throughput and cost-effective enzyme screening assays.