Chromatin is the complex of DNA and proteins that comprises the physiological form of the genome. Non-covalent interactions between DNA and histone proteins are necessary to compact large eukaryotic genomes into relatively small cell nuclei. The nucleosome is the fundamental repeating unit of chromatin, and is composed of 147bp of DNA wrapped around an octamer of histone proteins: 2 copies of each H2A, H2B, H3 and H4.
Approximately 1,700 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. Contact us to add your most recent publications to this collection.
February 2018
Biological Small-angle X-ray Scattering (BioSAXS)
BL4-2
February 2018
Li-ion batteries (LIBs) are key components of portable electronic devices, as well as in electric vehicles, military and medical equipment, backup power supplies, and even grid storage. However, the energy storage capacity and rate capability of current LIBs is still too low to meet the increasing demand of key markets. For the latter, the properties of the electrolyte-electrode interface play a decisive role.
X-ray reflectivity
BL7-2
January 2018
Since the discovery of unconventional high-temperature superconductivity (HTSC) in cuprates, one of the central questions in high Tc research is the nature of the “normal state” which develops into HTSC. As one of the pursuits of normal state properties, the recent observation of charge density wave (CDW) order is expected to shed light on the nature of the competing phases in high Tc cuprates. For this reason, CDW order in hole-doped cuprates has been actively studied by various experimental techniques such as neutron and x-ray scattering, scanning tunneling microscopy (STM), nuclear magnetic resonance (NMR), quantum oscillation, and ultrasound experiments. Among those techniques, x-ray scattering uniquely characterizes the spatial arrangement and strength of the charge density wave.
Angle-resolved photoelectron spectroscopy
BL5-2, BL13-3
November 2017
The materials and devices used in modern society are often structurally complex and chemically heterogeneous. The complexity in the material is usually caused by the desired functionality that has requirements in many different aspects of the material properties. Taking Li-ion battery as an example, the device is often evaluated by combining several different characteristics, including the energy density, capacity, cyclability, temperature stability, price etc. As a result, material scientists need to look into the realistic systems, in which both the anticipated and the unanticipated material phases/reactions occur.
BL4-1, BL6-2c
October 2017
The search continues for solar energy materials that are efficient and inexpensive and simple to make. Films made of metal halide perovskite crystals are good candidates because of their impressive solar cell efficiencies and their low cost to produce. An advantage of metal halide perovskite materials is the ability to tune their band gap, which determines the wavelengths of light that can be collected by the solar cell.
X-ray diffraction
BL11-3
October 2017
Cellular metabolism is essential for life. Up until recently, we knew just two methods cells use to generate and conserve the energy required for cellular metabolism: ATP hydrolysis and electrochemical ion potential across cell membranes. Recently, a paradigm-changing third mechanism was discovered, called flavin-based electron bifurcation (FBEB).
Macromolecular Crystallography
BL12-2
September 2017
Iron-sulfur (Fe-S) clusters are cofactors that are required for the function of proteins in many critical cellular processes. All living organisms synthesize and distribute Fe-S clusters using complex biosynthetic pathways. In humans, the mitochondrial cysteine desulfurase, NFS1, is responsible for the conversion of the sulfur-containing amino acid, cysteine, to alanine and persulfide sulfur, an intermediate in Fe-S cluster synthesis. In contrast to the analogous cysteine desulfurase in prokaryotes, the eukaryotic NFS1 enzyme requires accessory proteins, ISD11 and ACP, for its function. A team of scientists investigated the structure of the NFS1-ISD11-ACP complex in order to unravel NFS1’s requirement of ISD11 and ACP for function.
Macromolecular Crystallography
BL7-1
September 2017
Given our increasing dependence of rechargeable battery containing electronic devices, including electric cars, it is important to engineer these systems to mitigate potential for catastrophic battery failure. One possible source of lithium ion battery failure is over-discharge (over-lithiation) of the cathode, which can permanently damage the battery. Electronic battery management systems are programmed to prevent and identify such failures, but sometimes do not catch problems of over-lithiation when they occur. To better understand the characteristics of battery failure from over-discharging, a team of scientists studied the chemical and morphological changes that occur from over-lithiation of a lithium battery cathode.
X-ray Absorption Spectroscopy
BL4-1
August 2017
CRISPR, a powerful new tool that can target and change specific sequences of DNA, is based on a prokaryotic immune system response. The first step of bacterial immunity via CRISPR is placing sequences of foreign (viral) DNA between specific palindromic DNA repeats in the bacterial genome. The enzyme complex Cas1-Cas2 must target the correct DNA locus for integration, since insertion of the viral DNA into other areas of the genome may cause damage to the bacteria.
Macromolecular Crystallography
BL9-2
August 2017
Bacterial cells have subcellular features that function as organelles called microcompartments. Bacterial microcompartments organize cellular metabolism. These compartments help increase reaction rates by colocalizing reaction components. They can also sequester sensitive or damaging reactants or products from the rest of the cell. Part of bacterial microcompartment function is to allow only some molecules to cross into the compartment while keeping out others. How this selectivity is possible is not well understood.
Macromolecular Crystallography
BL12-2
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