Life is mostly composed of the elements carbon, hydrogen, nitrogen, oxygen, sulfur, and phosphorous. Although these six elements make up biomolecules such as nucleic acids, proteins, and lipids, it is theoretically possible that some other elements in the periodic table could serve similar functions. In a paper published in Science, Wolfe-Simon et. al., describe a bacterium of the Halomonadaceae family, strain GFAJ-1 which appears to substitute arsenic for phosphorous to sustain its growth.
Approximately 1,600 scientists visit SSRL annually to conduct experiments in broad disciplines including life sciences, materials, environmental science, and accelerator physics. Science highlights featured here and in our monthly newsletter, Headlines, increase the visibility of user science as well as the important contribution of SSRL in facilitating basic and applied scientific research. Many of these scientific highlights have been included in reports to funding agencies and have been picked up by other media. Users are strongly encouraged to contact us when exciting results are about to be published. We can work with users and the SLAC Office of Communication to develop the story and to communicate user research findings to a much broader audience. Visit SSRL Publications for a list of the hundreds of SSRL-related scientific papers published annually and to add your most recent publications to this collection.
While we continue to refine our science highlights content you may access older science summaries that date between 04/2001 to 06/2010 by visiting http://www-ssrl.slac.stanford.edu/science/sciencehighlights.html. We will be offering science summaries that date from 06/2012 to the present soon.
December 2010
X-ray Absorption Spectroscopy
BL2-3
December 2010
Nephrogenic systemic fibrosis, or NSF, is a relatively new disease in which the skin becomes hardened, joint movement becomes difficult and, in extreme cases, an excessive and sometimes fatal fibrosis tissue forms around organs. So far, NSF has only been observed in patients with kidney dysfunction who have undergone an MRI that required the injection of gadolinium-based contrast agents (GBCAs). Researchers speculate that the patient's kidneys cannot break down the gadolinium, causing NSF, but until now there has been no direct evidence for such a link.
X-ray microscopy, X-ray Absorption Spectroscopy
BL2-3
November 2010
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.
Scanning transmission x-ray microscopy
BL6-2, BL10-2
November 2010
Our bodies heavily rely on calcium ions (Ca2+). Their concentration in the cell cytoplasm is normally low under resting conditions, and its influx through specialized ion channels drives many functions ranging from muscle contraction, regulating heart beats, secretion of hormones and neurotransmitter, transcription of specific genes, and more. Ca2+ can enter the cytoplasm either from the extracellular space, or from intracellular stores. One such store is the ER (endoplasmic reticulum) and its membrane contains Ca2+ selective ion channels that open under controlled conditions. The main channel that regulates the Ca2+ release from the ER is the Ryanodine Receptor (RyR), a huge protein up to 2.2 MDa in size that generates the bulk Ca2+ signal required for the contraction of both skeletal and cardiac muscle.
Macromolecular Crystallography
BL9-2
October 2010
A desire to create machines that can explore their environments, like people do, through the sensations of feeling and touch, has inspired researchers to develop artificial skin. An ideal electronic skin would be flexible and sensitive to even minor touches, such as the weight of an insect. Such a touch-sensitive material could be used for human prosthetics, sensory input devices for robotics, and applications where the biologic and electronic communicate.
October 2010
MATE transporters are responsible for the exportation of various substrates and toxins from cells of bacteria, plants, and mammals using a proton or sodium gradient. Plants use them to transport metabolites, and they are important for tolerance to aluminum in soil, an important factor for crop yield. In bacteria and mammals, MATE transporters are important for multiple-drug resistance, which affects the efficacy of many medicines. Although these transporters play such important roles, much about how they work is not understood.
Macromolecular Crystallography
BL11-1
September 2010
X-ray microscopy is a useful tool for visualizing functional materials on the nanoscale. X-ray holography replaces the lens with a computer and obtains an image by Fourier inversion of the interference pattern. While in principle the resolution limit is given by the x-ray wavelength, in practice, the resolution is limited by the size of the reference being used.
Fourier Transform Holography, X-ray microscopy
BL13-3
September 2010
Semaphorins are a group of proteins known for their critical role in nerve and vascular development and are bound by signaling receptors called Plexins. Some Semaphorins, including Sema7A, are involved in a variety of immune responses. Vaccinia virus, which is used in the smallpox vaccine, has a Sema7A homologue called A39R, which binds PlexinC1, Sema7A's receptor.
Macromolecular Crystallography
BL9-2, BL11-1
August 2010
Three dimensional topological insulators are new state of quantum matter with a bulk gap and odd number of relativistic Dirac fermions on the surface. In the presence of the time reversal symmetry, these Dirac fermions are massless with a continuous Dirac point (Fig. 1a), immune to perturbations as long as the disorder potential does not violate the time reversal symmetry.
BL5-4
August 2010
Discovering high performing organic semiconductors is a hot area of research, as we look for efficient, low-cost materials that can be used in inexpensive electronic devices, such as flexible solar cells and radio frequency ID tags. To design effective materials, the relationship between a material’s structure and its semiconductive properties must be found. Research on p-type (hole conducting) organic semiconductors has shown π-bond stacking to be important in determining the semiconducting properties. The newer, n-type (electron conducting) class of organic semiconductors has not been as extensively studied.
BL2-1, BL7-2, BL11-3
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