DIRECT IN-SITU MEASUREMENT OF PHOSPHOLIPID HYDRATION IN AN AQUEOUS ENVIRONMENT USING A QUARTZ-CRYSTAL MICROBALANCE

Hydration of phospholipid head groups is essential for stabilizing bil ayer structures in au aqueous environment Here we describe a new, easy , and rapid method that can directly and quantitatively determine phos pholipid hydration in both water vapor and liquid water; i.e., a quart z crystal microbalance is employed which enables hydration to be deter mined in only 1 h using just 1 mu g of phospholipids under various env ironmental conditions, Dipalmitoylphosphatidylethanolamine (DPPE) was examined with varying temperature, KCI concentration, and phase of wat er, where it was found that DPPE hydration in liquid water markedly in creases upon raising the temperature, even when the phospholipid is in a gel phase, being maximal around its phase transition temperature (6 3.5 degrees C), Furthermore, KCl addition increased DPPE hydration in a temperature-dependent manner. The method presented is demonstrated t o be capable of determining phospholipid hydration under physiological conditions; hence, it is suitable for investigating hydration phenome na involved in biological processes.