Two-dimensional (2D) metals are an emerging class of nanostructures that have attracted enormous research interest due to their unusual electronic and thermal transport properties. Adding mesopores in the plane of ultrathin 2D metals is the next big step in manipulating these structures because increasing their surface area improves the utilization of the material and the availability of active sites. Here, we report a novel synthetic strategy to prepare an unprecedented type of 2D mesoporous metallic iridium (Ir) nanosheet. Mesoporous Ir nanosheets can be synthesized with close-packed assemblies of diblock copolymer (poly-(ethylene oxide)- b-polystyrene, PEO- b-PS) micelles aligned in the 2D plane of the nanosheets. This novel synthetic route opens a new dimension of control in the synthesis of 2D metals, enabling new kinds of mesoporous architectures with abundant catalytically active sites. Because of their unique structural features, the mesoporous metallic Ir nanosheets exhibit a high electrocatalytic activity toward the oxygen evolution reaction (OER) in acidic solution as compared to commercially available catalysts.

Aggregation and biofilm formation are critical mechanisms for bacterial resistance to host immune factors and antibiotics. Autotransporter (AT) proteins, which represent the largest group of outer-membrane and secreted proteins in Gram-negative bacteria, contribute significantly to these phenotypes. Despite their abundance and role in bacterial pathogenesis, most AT proteins have not been structurally characterized, and there is a paucity of detailed information with regard to their mode of action. Here we report the structure-function relationships of Antigen 43 (Ag43a), a prototypic self-associating AT protein from uropathogenic Escherichia coli. The functional domain of Ag43a displays a twisted L-shaped β-helical structure firmly stabilized by a 3D hydrogenbonded scaffold. Notably, the distinctive Ag43a L shape facilitates self-association and cell aggregation. Combining all our data, we define a molecular "Velcro-like" mechanism of AT-mediated bacterial clumping, which can be tailored to fit different bacterial lifestyles such as the formation of biofilms.Ag43 | virulence factor | structural biology | urinary tract infection

In 2012, preliminary guidelines were published addressing sample quality, data acquisition and reduction, presentation of scattering data and validation, and modelling for biomolecular small-angle scattering (SAS) experiments. Biomolecular SAS has since continued to grow and authors have increasingly adopted the preliminary guidelines. In parallel, integrative/hybrid determination of biomolecular structures is a rapidly growing field that is expanding the scope of structural biology. For SAS to contribute maximally to this field, it is essential to ensure open access to the information required for evaluation of the quality of SAS samples and data, as well as the validity of SAS-based structural models. To this end, the preliminary guidelines for data presentation in a publication are reviewed and updated, and the deposition of data and associated models in a public archive is recommended. These guidelines and recommendations have been prepared in consultation with the members of the International Union of Crystallography (IUCr) Small-Angle Scattering and Journals Commissions, the Worldwide Protein Data Bank (wwPDB) Small-Angle Scattering Validation Task Force and additional experts in the field.

Small-angle neutron scattering with contrast variation can fill important gaps in our understanding of biomolecular assemblies, providing constraints that can aid in the construction of molecular models and in subsequent model refinements. This paper describes the implementation of simple tools for analysing neutron contrast variation data, accessible via a user-friendly web-based interface (http:// www.mmb.usyd.edu.au/NCVWeb/). There are three modules accessible from the website to analyse neutron contrast variation data from bimolecular complexes. The first module, Contrast, computes neutron contrasts of each component of the complex required by the other two modules; the second module, R g , analyses the contrast dependence of the radii of gyration to yield information relating to the size and disposition of each component in the complex; and the third, Compost, decomposes the contrast variation series into composite scattering functions, which contain information regarding the shape of each component of the complex, and their orientation with respect to each other. computer programs J. Appl. Cryst. (2008). 41, 222-226 Andrew E. Whitten et al. MULCh 225 Figure 3Comparison between actual (solid line) and composite P(r) (dotted line) profiles for: Sda (top); KinA (middle); cross-term (bottom).

Cardiac myosin-binding protein C (cMyBP-C) is an accessory protein of striated muscle sarcomeres that is vital for maintaining regular heart function. Its 4 N-terminal regulatory domains, C0-C1-m-C2 (C0C2), influence actin and myosin interactions, the basic contractile proteins of muscle. Using neutron contrast variation data, we have determined that C0C2 forms a repeating assembly with filamentous actin, where the C0 and C1 domains of C0C2 attach near the DNase I-binding loop and subdomain 1 of adjacent actin monomers. Direct interactions between the N terminus of cMyBP-C and actin thereby provide a mechanism to modulate the contractile cycle by affecting the regulatory state of the thin filament and its ability to interact with myosin.familial hypertrophic cardiomypathy ͉ C protein ͉ muscle regulation ͉ neutron contrast variation ͉ small-angle scattering I nterest in cardiac myosin-binding protein C (cMyBP-C) has been stimulated in recent times because of its influence on fine-tuning heart muscle contraction and its links to inherited cardiac disorders (1). Medical research estimates that up to 1 in 500 adolescents and young adults is affected by the diverse genetic condition known as familial hypertrophic cardiomyopathy (FHC) (2), which presents as a gradual thickening of the ventricle walls of the heart and a correlated increase in the risk of heart failure. Approximately 63% of FHC cases are attributable to mutations in genes that encode sarcomeric proteins, the majority of which (42%) are mutations in the MYBPC3 gene (3). Of the 150 known FHC-causing mutations distributed throughout the MYBPC3 gene, 26 are located in the region that encodes the 4 N-terminal domains of the protein.The primary components of muscle thick and thin filaments are the proteins myosin and actin, respectively. Muscle shortens and develops force as thin filaments slide past thick filaments via the cyclic interactions of myosin cross-bridges (myosin-S1) extending from the thick filament to actin. These actomyosin interactions are regulated in part by calcium signals that are transmitted via thin-filament accessory proteins troponin and tropomyosin, whose movement on the thin filament unveils myosin-binding sites, permitting productive (weak to strong binding) cross-bridge transitions (4). Originally identified as a thick filament accessory protein, myosin-binding protein C (MyBP-C) also provides a thick-filament accessory protein, provides an additional regulatory layer to the contractile cycle, but the precise molecular mechanisms by which it influences actomyosin interactions are not understood. Belonging to the Ig/fibronectin superfamily of proteins, cMyBP-C consists of 11 sequentially ordered domains (C1, m, C2-C10, common to all isoforms), plus a cardiac specific N-terminal domain (C0) and proline/alanine-rich region that links C0 to C1. The N-terminal domains (C0-C1-m-C2 or C0C2) perform the regulatory functions by influencing myosin head interactions with actin filaments (5-7), whereas the C-terminal domains of cMyBP-C (C7-C10...

Copper resistance is a key virulence trait of the uropathogen Proteus mirabilis. Here we show that P. mirabilis ScsC (PmScsC) contributes to this defence mechanism by enabling swarming in the presence of copper. We also demonstrate that PmScsC is a thioredoxin-like disulfide isomerase but, unlike other characterized proteins in this family, it is trimeric. PmScsC trimerization and its active site cysteine are required for wild-type swarming activity in the presence of copper. Moreover, PmScsC exhibits unprecedented motion as a consequence of a shape-shifting motif linking the catalytic and trimerization domains. The linker accesses strand, loop and helical conformations enabling the sampling of an enormous folding landscape by the catalytic domains. Mutation of the shape-shifting motif abolishes disulfide isomerase activity, as does removal of the trimerization domain, showing that both features are essential to foldase function. More broadly, the shape-shifter peptide has the potential for ‘plug and play’ application in protein engineering.

Understanding how mesoporous noble metal architectures affect electrocatalytic performance is very important for the rational design and preparation of high-performance electrocatalysts.

Small-angle X-ray and neutron scattering (SAXS and SANS) are techniques used to extract structural parameters and determine the overall structures and shapes of biological macromolecules, complexes and assemblies in solution. The scattering intensities measured from a sample contain contributions from all atoms within the illuminated sample volume including the solvent and buffer components as well as the macromolecules of interest. In order to obtain structural information, it is essential to prepare an exactly matched solvent blank so that background scattering contributions can be accurately subtracted from the sample scattering to obtain the net scattering from the macromolecules in the sample. In addition, sample heterogeneity caused by contaminants, aggregates, mismatched solvents, radiation damage or other factors can severely influence and complicate data analysis so it is essential that the samples are pure and monodisperse for the duration of the experiment. This Protocol outlines the basic physics of SAXS and SANS and reveals how the underlying conceptual principles of the techniques ultimately 'translate' into practical laboratory guidance for the production of samples of sufficiently high quality for scattering experiments. The procedure describes how to prepare and characterize protein and nucleic acid samples for both SAXS and SANS using gel electrophoresis, size exclusion chromatography and light scattering. Also included are procedures specific to X-rays (in-line size exclusion chromatography SAXS) and neutrons, specifically preparing samples for contrast matching/variation experiments and deuterium labeling of proteins. * Primary corresponding author: cy.jeffries@embl-hamburg.de. Contributions.CMJ, MAG, CB, DBL, AEW and DIS helped develop SAXS and SANS sample preparation protocols and analytical tools. CMJ, MAG, CB, and DIS performed radiation damage studies and developed protocols for SEC-SAXS. CMJ, AEW and DBL contributed to 'in house' 2 H-labelling protocols. DBL, AEW, CMJ and DIS optimised protocols for preparing samples for SANS with contrast variation. AEW developed Contrast. CMJ, MAG, CB, DBL, AEW and DIS critically discussed and wrote the manuscript.