Snakes on a plane:
This atomic-resolution simulation of a two-dimensional peptoid nanosheet
reveals a
snake-like structure never seen before. The nanosheet’s layers include a
water-repelling
core (yellow),
peptoid backbones (white), and charged sidechains (magenta and cyan). The right
corner of the top
layer of the nanosheet has been “removed” to show how the backbone’s
alternating
rotational states
give the backbones a snake-like appearance (red and blue ribbons). Surrounding
water molecules
are red and white. (Credit: Ranjan Mannige, Berkeley Lab)
Computer sims and microscopy research at Berkeley Lab yield
first atomic-resolution structure of a peptoid nanosheet
(October 7, 2015) Scientists
aspire to build nanostructures that mimic the complexity and function of
nature’s proteins, but are made of durable and synthetic materials. These
microscopic widgets could be customized into incredibly sensitive chemical
detectors or long-lasting catalysts, to name a few possible applications.
But as with any craft that requires extreme precision,
researchers must first learn how to finesse the materials they’ll use to build
these structures. A discovery by scientists from the Department of Energy’s
Lawrence Berkeley National Laboratory (Berkeley Lab), and reported Oct. 7 in
the advance online publication of the journal Nature, is a big step in this
direction.
The Molecular
Foundry scientists who helped discover a new nano design rule.
From left, Ellen
Robertson, Alessia Battigelli, Ron Zuckermann, Caroline Proulx,
Stephen Whitelam,
and Ranjan Mannige. (Credit: Roy Kaltschmidt, Berkeley Lab)
The scientists discovered a design rule that enables a
recently created material to exist. The material is a peptoid nanosheet. It’s a
flat structure only two molecules thick, and it’s composed of peptoids, which
are synthetic polymers closely related to protein-forming peptides.
The design rule controls the way in which polymers adjoin to
form the backbones that run the length of nanosheets. Surprisingly, these
molecules link together in a counter-rotating pattern not seen in nature. This
pattern allows the backbones to remain linear and untwisted, a trait that makes
peptoid nanosheets larger and flatter than any biological structure.
The Berkeley Lab scientists say this never-before-seen
design rule could be used to piece together complex nanosheet structures and
other peptoid assemblies such as nanotubes and crystalline solids.
A simulation of a
peptoid nanosheet, shown first from a top-down view with the peptoid
backbones colored
to highlight their snake-like structure. The view then rotates to the side,
and finally
transitions to an all-atom representation. (Credit: Ron Zuckermann and
Ranjan Mannige,
Berkeley Lab)
What’s more, they discovered it by combining computer
simulations with x-ray scattering and imaging methods to determine, for the
first time, the atomic-resolution structure of peptoid nanosheets.
“This research suggests new ways to design biomimetic
structures,” says Steve Whitelam, a co-corresponding author of the Nature
paper. “We can begin thinking about using design principles other than those
nature offers.”
Whitelam is a staff scientist in the Theory Facility at the
Molecular Foundry, a DOE Office of Science user facility located at Berkeley
Lab. He led the research with co-corresponding author Ranjan Mannige, a
postdoctoral researcher at the Molecular Foundry; and Ron Zuckermann, who
directs the Molecular Foundry’s Biological Nanostructures Facility. They used
the high-performance computing resources of the National Energy Research
Scientific Computing Center (NERSC), another DOE Office of Science user
facility located at Berkeley Lab.