An international research team led by Lawrence Livermore atmospheric scientists found that smaller volcanic eruptions have contributed to a “warming hiatus” over the last 16 years. The warmest year on record was 1998. After that, the steep climb in global surface temperatures observed in the 20th century appeared to level off. Scientists had previously suggested that factors such as increased heat uptake by the oceans and weak solar activity could be responsible for the lull in temperature increases.
After publication of a 2011 paper in the journal Science, increased volcanic activity was implicated in the warming hiatus. Prior to the 2011 paper, the prevailing view was that only very large eruptions were capable of impacting global climate. Scientists have long recognized that erupting volcanoes cool the atmosphere by expelling sulfur dioxide, which combines with oxygen in the upper atmosphere to form droplets of sulfuric acid. These droplets can persist for many months, reflecting sunlight and lowering temperatures at Earth’s surface and in the lower atmosphere.
The new research, published in Geophysical Research Letters, further identifies observational climate signals caused by recent volcanic activity. Positive signal detection supports recent findings indicating that a series of small 21st-century volcanic eruptions deflected substantially more solar radiation than previously estimated. Says Livermore’s Benjamin Santer, lead author of the recent study, “This new work shows that late 20th- and early 21st-century volcanic activity produced discernible signals in observed temperature, moisture, and reflected sunlight at the top of Earth’s atmosphere.”
Contact: Benjamin Santer (925) 423-2253 (santer1@llnl.gov).
Livermore scientists participated in research that captured the highest resolution snapshots of a protein ever taken with an x-ray laser. The experiment, conducted at the Department of Energy’s SLAC National Accelerator Laboratory, revealed how a protein from photosynthetic bacteria changes shape in response to light.
SLAC’s Linac Coherent Light Source (LCLS) generated x-ray laser pulses about a billion times brighter than x rays from traditional synchrotrons. The fleeting pulses allowed researchers to see atomic-scale details of how the bacterial protein, called photoactive yellow protein or PYP, changes within millionths of a second after exposure to light. Crystallized samples of the protein, measuring about 2 millionths of a meter long, were sprayed into the path of the x-ray laser beam. Some of the crystallized proteins were exposed to blue light to trigger shape changes. The incident x rays produced diffraction patterns as they struck the crystals and were used to reconstruct the protein’s three-dimensional structure. Researchers then compared the structures of the light-exposed proteins to structures of proteins not illuminated by the blue light. Snapshots taken at different points in time were compiled into detailed movies.
The experiment marked the first time that the LCLS has been used to directly observe a protein’s structural changes at such a high resolution, says Matthias Frank, one of three participating Livermore researchers, along with Mark Hunter and Brent Segelke. Frank says the experimental results demonstrated that x-ray laser crystallography can be used to probe the atomic-scale details of biological molecules important to medicine and pharmacological research. The team’s results were published in the December 5, 2014, issue of Science.
Contact: Matthias Frank (925) 423-5068 (frank1@llnl.gov).
Lawrence Livermore researchers, together with collaborators from the University of California, Los Angeles, have discovered that some algae cells build an intracellular compartment to store metals and thereby maintain equilibrium. “We don’t understand very well how cells maintain balance when the cell is stressed by metal excess or metal deficiency,” says Livermore researcher Jennifer Pett-Ridge. “By storing the metal in a special intracellular compartment, the cell creates a bit of a pantry cupboard for itself and can better maintain its equilibrium.” How this matchmaking of metals and proteins occurs with precision has puzzled cell biologists.
The researchers shed light into how such pantry cupboards are maintained even under stressful conditions of metal deprivation. The research team studied the copper content in Chlamydomonas reinhardtii, a single-cell green alga. The organism’s copper concentration stays relatively constant over orders of magnitude of extracellular copper but hyperaccumulates when Chlamydomonas is starved for zinc.
To understand how a single cell builds a metal pantry, the team used high-resolution elemental imaging. The tools included fluorescent metal sensors, transmission electron microscopy, and nanoscale secondary ion mass spectrometry (NanoSIMS), which is housed at Livermore. NanoSIMS was recently equipped with a Hyperion II ion source, which provides a one-of-a-kind capability to image metals with up to 50-nanometer lateral resolution. With these tools, the team discovered that the bulk of copper in zinc-deficient cells is concentrated in the so-called pantry, hidden from cellular sensors. When the zinc starvation stress is relieved, copper is released and is used preferentially over extracellular sources of copper for biosynthesis.
Contact: Jennifer Pett-Ridge (925) 424-2882 (pettridge2@llnl.gov).