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Newsletter No. 335 -
June 6, 2016 -
OTHER BIOPHYSICAL METHODS 

Reliable cryo-EM resolution estimation
A modified Fourier shell correlation (FSC) moehodology is introduced by Pawel Penczek, which is aimed addressing two fundamental problems that mar the use of FSC: the strong influence of mask-induced artifacts on resolution estimation and the lack of assessment of FSC uncertaninties stemming from the inability to determine the asscociated number of degrees of freedom. For details, please click the link.

New approach for  structure determination from tiny crystals
Many crystals can't be grown into crystals large enough for their atomic arrangements to be deciphered. To tackle this challenge, scientists at the U.S. DOE's Brookhaven National Laboratory and colleagues at Columbia University have developed a new approach for solving protein structure from tiny crystal. For details, please click the link.

Widening the Reach of Structural Biology

X-ray free electron laser (XFEL) features stobe-like pulses that are just a few millionths of a billionth of a second long and a billion times brighter than synchrotron X-ray. The Linac Coherent Light Source (LCLS), operated by Stanford University for the U.S. Department of Energy, is the world's first XFEL facility, where scientists take crisp pictures of atomic motions, watch chemical reactions unfold, probe the properties of materials, and explore fundamental processes in living things. Its performance over the first five years of operation has already provided a breathtaking array of world-leading results.

Micro-electron diffraction (MicroED) data is collected from small 3D microcrystals  using a very low electron dose and readily processed using MOSFLM. Using the MicroED approach, the structure of lysozyme was solved using at 2.5-angstrom resolution (PDB entry 3J6K)  and  the structure of the toxic core of alpha-synuclein was determined at 1.4-angstrom resolution (PDB entry 4RIL). For a review, please see Protein structure determination by MicroED.

Cryo-electron microscopy (CryoEM) is an ensemble of techniques allowing the observation of biological specimens in their native environment at cryogenic temperatures in EM. For a recent cryoEM structure at high resolution, please see 2.2 Å resolution cryo-EM structure of b-galactosidase in complex with a cell-permeant inhibitor. For an overview, please see CryoEM at IUCrJ: a new era.

Small-angle X-ray scattering (SAXS) is capable of delivering structural information of biological macromolecules and their complexes in solution, small or large. For a recent example, the SAXS model for a ~500-kDa RapA:RNA polymerase complex (~230 angstroms in its longest dimension), please see Allosteric Activation of Bacterial Swi2/Snf2 Protein RapA by RNA Polymerase: Biochemical and Structural Studies.

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