Stanford Synchrotron Radiation Lightsource

Protein enzymes can contain specific sites to bind copper atoms for a variety of purposes. Depending on the environment and role of the enzyme, different amino acid residues are employed to bind Cu(I).  Oxygenase enzymes employing Cu(I) often use both methionine (Met) and histidine (His) amino acids, while membrane transport proteins often use Met and not His. The identity and placement of the amino acids coordinating the Cu(I) atoms create different local environments, but it is unclear how this affects the Cu(I) atom to fulfill the role it serves for the enzyme or transporter.  A team of scientists has recently developed a new experimental approach to measure the local environmental effects on Cu(I) reactivity. 

The sun provides more energy than what could ever possibly be consumed. However, switching to solar energy to end our dependence on fossil energy resources is made difficult not merely by how much is consumed, but rather by the pattern of how energy is used: significant amounts are consumed by road and air transportation and must be provided “on board” in the form of fuels. This problem could be solved with new devices that convert sunlight into renewable fuels, for example, by driving a light-induced current between two electrodes that split water by electrolysis into hydrogen and oxygen. Currently, the limiting step for the viability of this process is the oxygen evolution reaction (OER) that takes place at the anode. 

It is common knowledge that materials expand when heated. However, a chemical compound known as BiNiO₃ proves to be quite extraordinary in that it contracts with rising temperature. By mixing BiNiO₃ with “conventionally” expanding materials, it becomes possible to produce composite materials with zero or other desired thermal expansion values – a possibility with great potential for engineering and other applications. The same transition from a low-density to a high-density phase of BiNiO₃ observed for increasing temperatures can also be induced by applying high pressure.

Li-ion batteries are key devices in the effort to develop efficient chemical energy storage from sustainable energy sources. However, any effort to optimize battery performance requires a deeper understanding of the fundamental mechanisms of diffusion and phase transformation in battery electrodes.

Researchers at SSRL, General Motors, Imperial College London, National Taiwan University, and elsewhere have recently begun experimenting with 3-D transmission X-ray microscopy (TXM), in order to gain new insight into the microstructure of battery electrodes.

The FeFe-hydrogenases are of great interest because they can catalyze both the forward and reversed dihydrogen uptake/evolution reactions. Under optimal conditions a single molecule of FeFe-hydrogenase can produce approximately 9000 molecules of hydrogen per second. This translates into a theoretical capacity for refueling the hydrogen tank of the Space Shuttle within 30 minutes. Thus, hydrogenases are considered as desirable biological targets for hydrogen-based energy production and utilization technologies.

An international collaboration that included researchers at SSRL has used x-ray scanning microprobe fluorescence techniques at BL6-2 to characterize the elemental chemistry of samples from comet 81P/Wild-2 brought back aboard the Stardust spacecraft last January. Twenty-three aerogel samples containing cometary particles were analyzed by the 175-member Preliminary Examination Team, and five of those samples were studied at SSRL. This collaboration provided the first look at the Stardust samples after the return, and results are presented in several publications in the December 15 issue of Science.

An early transcription of Archimedes' mathematical theories has been brought to light through the probing of high-intensity x-rays at SSRL's BL6-2. The text contains part of the Method of Mechanical Theorems, one of Archimedes' most important works, which was probably copied out by a scribe in the tenth century. The parchment on which it was written was later scraped down and reused as pages in a twelfth century prayer book, producing a document known as a palimpsest (which comes from the Greek, meaning 'rubbed smooth again').

Proteins containing iron-sulfur clusters are ubiquitous in nature and catalyze one-electron transfer processes. These proteins have evolved into two classes that have large differences in their electrochemical potentials: high potential iron-sulfur proteins (HiPIPs) and bacterial ferredoxins (Fds). The role of the surrounding protein environment in tuning these redox potentials has been a persistent puzzle in the understanding of biological electron transfer. Although high potential iron-sulfur proteins and ferredoxins have the same iron-sulfur structural motif, there are large differences in their electrochemical potentials.

The continuous advancement of X-ray spectroscopic techniques allows us to probe the structure of biological machineries for smaller samples in more dilute concentrations and thus to ask tough scientific questions about problems that have not been possible in the past. Careful biochemical preparation and systematic analytical characterization resulted in galactose oxidase samples that could be interrogated by X-rays. This metalloenzyme contains a copper at its active site that is coordinated to a cross-linked tyrosine and cysteine ligand, which both are essential to convert alcohols and sugars to their oxidized aldehyde forms by oxygen molecule. The remarkable feature of this reaction that it is selective and does not results in formation of carboxylates (a form of vinegar).

The advent of photosynthesis gave life forms a new way to capture energy from the sun. The by-product of the success of photosynthesis, an abundance of dioxygen (O₂) in our atmosphere allowed aerobic creatures, including humans, to evolve and prosper. This process transformed the history of life on Earth. The oxidation of water to O₂ is catalyzed by the oxygen-evolving complex (Mn₄O_xCa cluster) in the membrane protein, photosystem II (PSII).

The 3D structure of bone is critical for maintaining strength. Skeletal diseases such as osteoporosis and environmental conditions such as weightlessness, radiation, and vitamin D deficiency can affect bone structure. Understanding the 3D structure of bone is critical to understanding how these conditions affect bone's form and function.

Rice, the grain that provides more than one-fifth of the world population's calories, can become a health hazard if contaminated with arsenic. Such contamination, a surprisingly widespread occurrence, takes place in areas where soil or irrigation water is tainted by naturally occurring arsenic--including broad swaths of south and southeastern Asia. Studies have suggested that the natural iron coating around the roots of rice plants may serve as an important barrier to arsenic uptake because arsenic in its oxidized form has an affinity for iron. A team of Stanford and SSRL researchers recently sought to learn just how significant a barrier iron provides.

As an important step toward reducing oil dependence and greenhouse gas production, electric vehicles are becoming more and more prevalent. However, one major barrier remains: their batteries. Today’s lithium-ion technology has yet to meet energy density, cost, life cycle and safety goals.

If we could make plant food from nitrogen the way nature does, we would have a much greener method for manufacturing fertilizer; the current industrial process requires such high temperatures and pressures that it consumes about 1.5 percent of the world’s energy. Now scientists working at the Stanford Synchrotron Radiation Lightsource have taken an important step toward understanding how nature performs this reaction, by establishing the nature of a key atom that researchers had sought to identify for more than a decade.

When we think of chlorine, we often relate it to the salt used in food preparation, chloride in the oceans, chlorine gas from swimming pools, and gaseous chlorofluorocarbons that have close links to the depletion of stratospheric ozone. We rarely think of thousands of chlorinated hydrocarbons that exist in the natural systems, several of which are highly toxic to humans (1). The C-Cl bond, common to all organo-Cl compounds, is strong and gives high stability to organo-Cl compounds. For this reason, several organo-Cl compounds have been synthesized and used extensively for years in agricultural and industrial applications.

Sulfur is essential for all life, but it plays a particularly central role in the metabolism of many anaerobic microorganisms. Prominent among these are the sulfide-oxidizing bacteria that oxidize sulfide (S2-) to sulfate (SO42-). Many of these organisms can store elemental sulfur (S0) in "globules" for use when food is in short supply (Fig. 1). The chemical nature of the sulfur in these globules has been an enigma since they were first described as far back as 1887 (1); all known forms (or allotropes) of elemental sulfur are solid at room temperature, but globule sulfur has been described as "liquid", and it apparently has a low density – 1.3 compared to 2.1 for the common yellow allotrope α-sulfur.