Lysozyme (shown in blue)—a natural enzyme found in tears, saliva, and egg whites—can break down bacterial cell walls (shown in pink). ORNL researchers have combined computational simulation and neutron experiments to clarify the complicated motions of proteins such as lysozyme into three distinct classes. Image: Oak Ridge National Laboratory |
Molecular motion in proteins comes in three
distinct classes, according to a collaboration by researchers at the Department
of Energy’s Oak Ridge National Laboratory (ORNL) and the University of Tennessee,
in research reported in Physical Review
Letters.
The research team, directed by ORNL-UT
Governor’s Chairs Jeremy Smith and Alexei Sokolov, combined high-performance
computer simulation with neutron scattering experiments to understand
atomic-level motions that underpin the operations of proteins.
“The analysis and interpretation of
neutron scattering spectra are always difficult for complex molecules such as
proteins,” says Smith, who directs ORNL’s Center for Molecular Biophysics.
“We’ve performed experiments and then shown that simulation can provide a
clear view of them. It allows us to see through the complexity and find out
what motions are going on.”
Defining the motions present—localized
diffusion, methyl group rotations, and jumps—is important as it allows
scientists to think about how the motions determine the functions of proteins
that are critical to all life.
“First, we found that experiment and
simulation agreed perfectly with each other, which is remarkable,” Smith
says. “Second, the simulations told us that this type of neutron
scattering can be interpreted in a very simple way.”
Although the team performed its research on
a particular protein called lysozyme, a natural antibacterial enzyme found in
tears, saliva, and egg whites, the researchers anticipate the technique will
have a much broader impact in the neutron scattering community, aiding research
in areas such as biofuel design or environmental remediation.
The combined simulation and neutron
scattering approach should also be of use in the characterization of
non-biological materials such as polymers. Smith notes that approximately half
the neutron scattering experiments at ORNL’s Spallation Neutron Source involve
the study of motions in materials.
“These methods are of general
applicability,” Smith says. “Many experimentalists can now come to
the ORNL’s Spallation Neutron Source, measure a spectrum of whatever sample
they have, and then apply this analysis in terms of three classes of motion to
interpret their results.”
The research was primarily
conducted by ORNL’s Liang Hong, with the support of Benjamin Lindner and
Nikolai Smolin from ORNL. They performed neutron scattering experiments at
ORNL’s Spallation Neutron Source on the BASIS instrument and at the National
Institute of Standards and Technology
Center for Neutron
Research. The work was published as “Three classes of motion in the
dynamic neutron scattering susceptibility of a globular protein.”
