X-Ray and Ultrafast Science
Faster X-ray Pulses Promise Breakthrough Science
Just as scientists strive to manipulate matter at ever-smaller scales, they also strive to observe matter using ever-faster pulses of light. Called ultrafast science, the need for lightning-quick x-ray flashes lies in the fact that chemistry starts with the movement of electrons, a motion that takes place in a matter of attoseconds, a timescale almost too small to comprehend. An attosecond is one billionth of a billionth of a second, and there are more attoseconds in one minute than there have been minutes in the history of the universe.
Berkeley Lab scientists are working to bring x-ray science into these ultrafast time domains. They are already pioneers in developing x-ray pulses at the femtosecond scale, which is three orders of magnitude slower than attoseconds, but still fast enough to study the motion of atoms in molecules during physical, chemical, and biological reactions. Now, Berkeley Lab scientists are working to ratchet down the duration of coherent pulses of x-ray light to the attosecond level, which will make the hidden world of electron movement visible for the first time — and herald a new age of fundamental materials science and biological research.
Another cornerstone of Berkeley Lab’s x-ray science program is the Advanced Light Source (ALS), a national user facility that generates intense light for scientific and technological research. As the world’s brightest source of ultraviolet and soft x-ray beams — and the world’s first third-generation synchrotron light source in its energy range — the ALS makes previously impossible studies possible.
The ALS works by accelerating electrons to nearly the speed of light and bending them in a circular path by powerful magnets. At this speed, electrons emit extremely bright x-ray light that is directed along a beamline toward an object that researchers want to investigate at the atomic level, such as a crystallized protein. The pattern in which x-rays diffract off the protein reveals its structure. Ongoing research topics include investigating the electronic structure of matter, protein crystallography, ozone photochemistry, computer microchips, and optics testing.
Berkeley Lab scientists are also ensuring the ALS remains at the forefront of x-ray science.
About the Image
Protein Crystallography
The human genome has been sequenced, but the work has just begun. One of the big challenges in science is determining the function of the 30,000 proteins assembled by the human genome, as well as the genomes of other organisms — which is where the Advanced Light Source comes in. It’s a world leader in protein crystallography, a process in which extremely bright beams of light are used to elucidate a protein crystal’s structure, which can then be used to determine its function.
ALS images helped a Berkeley Lab team make new determinations about the process by which proteins are synthesized from the genetic code. The research team compared images of ribosomes taken from normal strains of the bacterium Escherichia coli to those of a mutant, antibiotic-resistant strain. Ribosomes are the molecules in living cells responsible for translating the genetic code into proteins.
Scientists are also inching closer to a cure for spinal cord injuries, thanks to a research team that used the ALS to determine the structure of a protein that prevents neurons from repairing themselves. The protein is dubbed the Nogo receptor because it binds with several other proteins that block neural growth. It’s found on the surface of thin fibers, called axons, which carry information between neurons in the brain and spinal cord. Resear-chers believe that if they can pharmaceutically block the interaction between the Nogo receptor and these growth-inhibiting proteins, then severed neurons may fuse back together, and paralyzed people might walk again.
In the race to stay one step ahead of drug-resistant bacteria, scientists from Berkeley Lab and UC Berkeley obtained high-resolution images of AcrB (left), a protein complex found in bacteria that repels a wide range of antibiotics. Even ciprofloxacin, an antibiotic used to treat a variety of bacterial infections including inhaled anthrax, is no match for AcrB—the green-colored drug (shown at left) is firmly ensnared in the protein’s cavity. The research may inform the development of antibiotics that either evade or inhibit these protein complexes, allowing drugs to slip inside bacteria cells and kill them.
To keep pace with the ever-growing demand for these stunning images, Berkeley Lab scientists were the first to automate the painstaking process of mounting and aligning protein crystals for study at a synchrotron. Such improvements have allowed ALS users to screen more than 10,000 protein crystals and collect complete structural datasets on several hundred of them.