New forensic DNA profiling technique on the horizon

A study recently conducted at the Circular Dichroism beamline (B23) here at Diamond Light Source could pave the way to a new forensic DNA profiling technique. Researchers hailing from the Ivanovo State University of Chemistry and Technology, Russia, The University of Southampton and Diamond investigated the application of specially designed DNA building blocks.

DNA is a versatile template that can be used for a variety of applications. It is made up of building blocks known as nucleotides (labelled A, C, G and T) which form long strands that bind to complementary sequences and give the familiar double helix. The nucleotides can be tailor made to build new functional molecules for biotechnology, analytics, or even materials science.

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Structural Mechanisms of Histone Recognition by Histone Chaperones

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.

Assembly of nucleosomes in the cell requires the coordinated effort of many proteins including ATP-dependent chromatin remodeling enzymes and ATP-independent histone chaperone proteins. Histone chaperones are a large class of proteins responsible for binding the highly basic histone proteins, shielding them from non-specific interactions, facilitating nuclear import of histones, and finally depositing histones onto DNA to form nucleosomes. Despite performing many overlapping functions, histone chaperone proteins are highly structurally divergent. However, nearly all histone chaperones contain highly charged intrinsically disordered regions (IDRs)1. In many cases truncation of these conserved regions results in loss of histone affinity and deposition functions.

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Image: (extract) SAXS analysis of Npm Core+A2 truncation (1-145) bound to five H2A/H2B dimers. Left: small angle x-ray scattering curve of the complex (purple dots). Simulated SAXS curve from the best scoring structural model shown as a black line. Right: SAXS envelope of the complex (pink) with the best scoring structural model inside. Positioning of H2A/H2B dimers by NMR and SAXS structural restraints. Full image here.

Molecular Movie

Researchers Create Molecular Movie of Virus Preparing to Infect Healthy Cells

With SLAC’s X-ray laser, scientists captured a virus changing shape and rearranging its genome to invade a cell.

A research team has created for the first time a movie with nanoscale resolution of the three-dimensional changes a virus undergoes as it prepares to infect a healthy cell. The scientists analyzed thousands of individual snapshots from intense X-ray flashes, capturing the process in an experiment at the Department of Energy’s SLAC National Accelerator Laboratory.

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