University of Illinois researchers said as water and ice cubes co-exist in a glass, a group of organic compounds called lipids can coexist as liquid and solid in membranes. That "patchiness" in phospholipid membranes is fundamental to their use as biomolecules and biosensors, the scientists said.

"We are seeing a previously unsuspected responsiveness in phospholipid membranes," said Professor Steve Granick. "What we thought was possible only with the specificity of certain proteins, we now see can happen with simple, charged nanoparticles."

Granick, graduate student Liangfang Zhang, graduate research assistant Bo Wang and research scientist Sung Chul Bae have shown a phospholipid membrane can coexist in two phases -- solid and liquid -- according to what binds to it. They said that inherent patchiness presents an additional mechanism for changing the stiffness of phospholipid membranes.

The researchers now intend to investigate novel ways to stabilize lipid membranes for targeted drug delivery.

The researchers report their work in a paper to be published next week in the online early edition of the Proceedings of the National Academy of Sciences.