Water Whips Proteins Into Shape

With the aid of far-infrared spectroscopy, researchers have taken a detailed look at how water molecules choreograph the intricate process of protein folding (Angew. Chem. Int. Ed. 2008, 47, 6486). A team led by Martin Gruebele at the University of Illinois, Urbana-Champaign, and Martina Havenith at Ruhr University, in Bochum, Germany, adapted a laser-based far-IR technique to monitor solvent dynamics during protein folding in real time. The researchers focused ultrashort laser pulses onto a solution of unfolded ubiquitin, a common regulatory protein, and initiated folding by diluting a denaturant in the buffer. The spectroscopic technique, which the team calls kinetic terahertz absorption, provided a picosecond-by-picosecond glimpse of water-protein hydrogen bonds breaking, as well as their replacement by protein-protein hydrogen bonds. This rearrangement helps organize the structure of a folding protein. The team found that motion from the solvent network of water molecules helped set up the right configuration, facilitating ubiquitin’s folding. The experimental data corroborates other researchers’ hypotheses that some protein and solvent dynamics are intertwined, the authors write.