Lawrence Livermore National Laboratory



Researchers Study Protein Filaments

To advance understanding of diseases such as Alzheimer’s and Parkinson’s, scientists have studied small protein filaments called amyloids, which can form fibrous clusters in the brain. Until now, even the best tools for studying amyloids have yielded only limited views of the filaments. However, an international research team including Livermore scientists Matthias Frank and Matt Coleman has developed a new method with the potential for revealing the detailed structure of individual amyloid fibrils using powerful beams of x-ray laser light. The method is described in a report published May 9, 2018, in Nature Communications.

Experiments were conducted at the Linac Coherent Light Source (LCLS). Although the team did not uncover the complete fibril structure, their innovative method opens a promising path for amyloid studies using x-ray free-electron lasers such as LCLS. The method leverages work by Frank and Coleman on novel sample supports. Previously, the team had developed sample supports based on small silicon chips with large numbers of small-area windows covered by ultrathin silicon nitride membranes to hold biological samples. For the LCLS work, the pair replaced the thin membranes on the chips with graphene, which is even thinner. Graphene is almost transparent to x rays, allowing the team to probe the delicate fibrils without significant extraneous signals from the graphene layer.

This new approach provided the solution to hold the fibril samples while supporting the graphene and scanning the material through the x-ray beam. Results at LCLS suggest that this technique may even be used in the future to determine the structure of individual amyloid fibrils.
Contact: Matthias Frank (925) 423-5068 (frank1@llnl.gov).

A Warm Look at Water’s Structure

Boiling water traditionally involves adding energy to the molecules by conduction, convection, or thermal radiation. Now Livermore scientists and collaborators have developed a way to use an x-ray free-electron laser (XFEL) to heat water to temperatures above 100,000 kelvins (179,540°F) and pressures above 100 gigapascals (1 million times Earth’s atmospheric pressure), where the liquid transitions into warm dense matter. The research appears online in the May 14, 2018, edition of the Proceedings of the National Academy of Sciences.

XFELs have opened the door to a new era in structural biology, enabling the imaging of biomolecules and dynamics that were impossible to access with conventional methods. Understanding the dynamics of warm dense matter benefits imaging in structural biology and can also provide insight into various fields such as inertial confinement fusion, planetary cores, shockwaves in dense material, and radiation damage in biological matter.

“This exotic ionic and disordered state of liquid density is structurally different from heating water the traditional way,” says Stefan Hau-Riege, Livermore physicist and coauthor of the paper. The ultrafast phase transition observed in water provides evidence that any biological structure exposed to these x-ray pulses is destroyed during x-ray exposure. This finding is significant because many imaging techniques for determining molecular structure use water or another liquid to deliver the sample into the x-ray interaction region.
Contact: Stefan Hau-Riege (925) 422-5892 (hauriege1@llnl.gov).

Prospecting for Antineutrinos

The Precision Reactor Oscillation and Spectrum Experiment (PROSPECT) has completed installation of a novel antineutrino detector that will probe the possible existence of a new form of matter—sterile neutrinos. (See image below.) PROSPECT, located at Oak Ridge National Laboratory, has begun taking data to study electron antineutrinos that are emitted from nuclear decays in a reactor to search for sterile neutrinos, and to learn about the underlying nuclear reactions that power fission reactors.

“The successful operation of PROSPECT will allow us to gain insight into one of the fundamental puzzles in neutrino physics and develop a better understanding of reactor fuel, while also providing a new tool for nuclear safeguards,” said cospokesperson Nathaniel Bowden, a Livermore scientist and expert in nuclear nonproliferation technology. The installation of PROSPECT follows four years of intensive research and development by a collaboration of more than 60 participants from 10 universities and 4 national laboratories.

The experiment uses a novel antineutrino detector system based on a segmented liquid scintillator technology. The combination of segmentation and a unique, lithium-doped liquid scintillator formulation allows PROSPECT to identify particle types and interaction points. These design features—along with extensive, tailored shielding—will enable PROSPECT to make a precise measurement of neutrinos in the high-background environment of a nuclear reactor. PROSPECT’s detector technology may therefore have applications in the monitoring of nuclear reactors for nonproliferation applications.
Contact: Nathaniel Bowden (925) 422-4923 (bowden20@llnl.gov).