The synthetic lipids self assembled to form a membrane mimicking a natural fat molecule. The unique assemblage creates tiny channels in which water is trapped in spaces too small for ice crystals to form, even at extremely cold temperatures. Photo by Peter Rüegg / ETH Zurich
April 10 (UPI) -- Scientists have discovered a way to keep water from freezing, even at extremely cold temperatures.
When water freezes, its molecules organize into a lattice pattern to form ice crystals. The molecules of liquid water remain disorganized, free-floating, allowing water to flow.
In the lab, scientists at the University of Zurich kept supercooled water in liquid form by trapping it inside a new kind of synthesized lipid.
Lipids are fat molecules. For the study, scientists developed a synthetic fat molecule called lipidic mesophase. The lipids self-assemble to form membranes that look and behave like natural fat molecules.
When the membranes aggregate, they form interconnected channels measuring less than a nanometer wide. The shape of the membrane assemblage depends on the temperature and water content.
In experiments, scientists determined water trapped inside the membrane's tiny channels can't freeze, even at subzero temperatures.
For one test, scientists used liquid helium to cool lipidic mesophase modified with monoacylglycerol to negative 263 degrees Celsius -- 10 degrees away from absolute zero. At the extreme subzero temp, the water became "glassy" but did not freeze.
The shape and the size of the channels formed by the self-assembling lipids depends on the water content, which is hard to control.
"What makes developing these lipids so tricky is their synthesis and purification," Ehud Landau, professor of chemistry at the University of Zurich, said in a news release.
Lipid molecules have one hydrophobic component, which repels water, and one hydrophilic component, which attracts water.
"This makes them extremely difficult to work with," Landau said.
To create the new class of lipids for their experiments, researchers modeled the synthetic fat molecules after the membranes of bacteria that can survive extremely cold temperatures.
"The novelty of our lipids is the introduction of highly strained three-membered rings into specific positions within the hydrophobic parts of the molecules," said Landau. "These enable the necessary curvature to produce such tiny water channels and prevent lipids to crystallize."
Scientists detailed their feat in the journal Nature Nanotechnology.
Authors of the new study expect their research to be utilized by other scientists. The lipids can be used to isolate, preserve and study large biomolecules, like proteins, in a membrane-like environment.
"Our research is paving the way for future projects to determine how proteins might be preserved in their original form and interact with lipid membranes at very low temperatures," said Zurich professor Raffaele Mezzenga.