Submitted to: Journal of Physical Chemistry
Publication Type: Peer reviewed journal
Publication Acceptance Date: 5/19/2008
Publication Date: 6/18/2008
Citation: Evans, K.O. 2008. Supported phospholipid membrane interactions with 1-butyl-3-methyl-imidazolium chloride. Journal of Physical Chemistry: B. 112:8558-8562. Interpretive Summary: To further utilize vegetable oils as new products, novel reaction conditions must be identified. Enzymes are often used to catalyze these reactions, but sometimes fail to provide the full scope of chemistry necessary to promote these novel reactions. Typically, the conversion of vegetable oils occurs via immobilization of an enzyme on an inert surface. However, some enzymes have shown a loss of activity when placed in room-temperature ionic liquids (liquid salts) which help the enzyme function on these surfaces. Protection of the enzyme can aid in maintaining its function. A typical protective agent for some enzymes is a lipid casing. Unfortunately, there is virtually no data that describes interactions between lipids and room-temperature ionic liquids on such surfaces. This work was conducted to try and shed light on such interactions. Results show that a common component of room-temperature liquid salts did not disturb lipid "bubbles" or thin lipid sheets on most surfaces. An exception was discovered to occur when a thin lipid sheet was formed from lipids in which two percent of the lipids had a negative charge and the inert surface was gold that was modified. These fundamental results will be used by us, and other scientists, as a foundation to better understand the conditions which allow a protective lipid layer to remain stable in a room-temperature ionic liquid.
Technical Abstract: Quartz crystal microbalance with dissipation measurements were conducted for 98/2 mole ratio of 1,2-dielaidoylphosphocholine (DEPC) and 1,2-dimyristoylphosphoglycerol (DMPG) on silica, gold and a self-assembled monolayer of 11-mercapto-1-undecanol and 11-mercaptoundecanoic acid at 50-mole% each. This study demonstrates that the presence of a marginal amount of DMPG was enough for a supported phospholipid bilayer to form on the self-assembled monolayer. Interactions of a supported phospholipid bilayer and intact vesicles with the room-temperature ionic liquid, 1-butyl-3-methyl imidazolium chloride, above its critical micelle concentration were discussed.