Researchers overcome the freezing sample problem in biostudies

Researchers at the Spallation Neutron Source BASIS beam line at the Department of Energy's Oak Ridge National Laboratory have successfully developed a method to study biomolecules (proteins) at temperatures far below freezing using a lithium chloride preparation in the aqueous solvent that prevents freezing.

Studying biosamples at supercold temperatures - 200 Kelvin - was previously impossible, as the water in such a solution inevitably freezes, and with it, the biosample's dynamic interactions freeze, too. The ability to study proteins at these temperatures gives researchers an important new avenue for understanding how they function in living organisms.

Neutron researchers need to study the dynamic interaction of proteins and their aqueous solvent at very low temperatures to understand their vibrational behavior at the atomic level. Then, while slowly raising the temperature to physiological conditions, they can study the unique biological "relaxational" motions that dominate as the temperature is raised.

Quasi-elastic neutron scattering (QENS) can then literally snap pictures as the dynamic interactions of the sample and water gradually "switch on" with the rise in temperature. How to keep the biosample from freezing at very low temperatures has been an ongoing research problem.

Now Eugene Mamontov, lead instrument scientist at the SNS's Backscattering Spectrometer (BASIS) and Xiang-qiang Chu, his postdoc of two years, have successfully navigated this research roadblock with a unique method that stops the hydrated biomolecule from freezing.

In a series of papers over several years, Mamontov and Chu had already shown that a lithium chloride aqueous solution is remarkably similar in its dynamics to pure water. And more significantly, they found that at very low temperatures, it does not freeze.