Livermore & NIH scientists create technique to examine behavior of proteins at single molecule level

A Lawrence Livermore National Laboratory physicist, in collaboration with an international team of researchers, has developed an experimental method that allows scientists to investigate the behavior of proteins under non-equilibrium conditions one molecule at a time, to better understand a fundamental biological process of protein folding that is important for many diseases.

The work, presented in the Aug. 29 edition of Science, marks the first time protein-folding kinetics has been monitored on the single-molecule level. Proteins are long chains of amino acids. Like shoelaces, they loop about each other or fold in a variety of ways, and only one way allows the protein to function properly. Just as a knotted shoelace can be a problem, a misfolded protein can do serious damage. Many diseases, such as Alzheimer’s, cystic fibrosis, mad cow disease and many cancers result from misfolded protein.

Livermore’s Lawrence postdoctoral fellow Olgica Bakajin worked with scientists from the NIDDK Laboratory of Chemical Physics at the National Institute of Health and the Physikalische Biochemie Universität Postadam in Germany to develop a microfluidic mixer for studies of protein folding. With this mixer, researchers were able to access information about the protein folding reaction that was never available from ensemble measurements or even from the newer single molecule equilibrium measurements.

“For the first time, in this experiment we were able to look at a protein on a single molecule level at defined times after the folding reaction was initiated,” Bakajin said. “With this method we are able to see and isolate intermediate states that under equilibrium conditions only exist for a brief period of time.

“This is a fundamental science project. We would like to understand the sequence of events through which a protein goes from a random coil to its functional ’folded’ form, and we’ve designed an instrument that can help us do this. Now the instrument can be used to study many different proteins so we can come up with some general rules as to how proteins fold.”

Understanding of protein folding will contribute to better understanding of the diseases, which in turn will lead to better treatments. Founded in 1952, Lawrence Livermore National Laboratory is a national security laboratory, with a mission to ensure national security and apply science and technology to the important issues of our time. Lawrence Livermore National Laboratory is managed by the University of California for the U.S. Department of Energy’s National Nuclear Security Administration.