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Molecular assemblies built with the artificial protein Pizza
No full textRecently an artificial protein named Pizza6 was reported, which possesses six identical tandem repeats and adopts a monomeric β-propeller fold with sixfold structural symmetry. Pizza2, a truncated form that consists of a double tandem repeat, self-assembles into a trimer reconstructing the same propeller architecture as Pizza6. The ability of pizza proteins to self-assemble to form complete propellers makes them interesting building blocks to engineer larger symmetrical protein complexes such as symmetric nanoparticles. Here we have explored the self-assembly of Pizza2 fused to homo-oligomerizing peptides. In total, we engineered five different fusion proteins, of which three appeared to assemble successfully into larger complexes. Further characterization of these proteins showed one monodisperse designer protein with a structure close to the intended design. This protein was further fused to eGFP to investigate functionalization of the nanoparticle. The fusion protein was stable and could be expressed in high yield, showing that Pizza-based nanoparticles may be further decorated with functional domain
An effective approach to electroweak baryogenesis
No full textThe asymmetry between matter and antimatter is one of the big outstanding questions of particle physics and cosmology. In this talk, I will argue that electroweak baryogenesis is an interesting mechanism to generate the baryon asymmetry. The new physics needed for electroweak baryogenesis come into play at a relatively low scale and can thus be tested in experiment.I will address three issues related to Electroweak baryogenesis. First I will explain whether electroweak baryogenesis can be studied in the model-independent framework of the Standard Model Effective Field Theory. Second, I will compare the contributions to the value of the asymmetry resulting from CP-violating interactions of different Standard Model particles. Third, I will discuss the validity of the so-called vev-insertion approximation, that is used to compute the value of the baryon asymmetry
Five-brane webs, Higgs branches and unitary/orthosymplectic magnetic quivers
No full textWe study the Higgs branch of 5d superconformal theories engineered from brane webs with orientifold five-planes. We propose a generalization of the rules to derive magnetic quivers from brane webs pioneered in arXiv:2004.04082, by analyzing theories that can be described with a brane web with and without O5 planes. Our proposed magnetic quivers include novel features, such as hypermultiplets transforming in the fundamental-fundamental representation of two gauge nodes, antisymmetric matter, and gauge nodes. We test our results by computing the Coulomb and Higgs branch Hilbert series of the magnetic quivers obtained from the two distinct constructions and find agreement in all cases
3D analysis of the myenteric plexus of the human bowel by X-ray phase-contrast tomography – a future method?
No full textObjectives: Light microscopical analysis in two dimensions, combined with immunohistochemistry, is presently the gold standard to describe the enteric nervous system (ENS). Our aim was to assess the usefulness of three-dimensional (3D) imaging by X-ray phase-contrast tomography in evaluating the ENS of the human bowel.Material and methods: Myenteric ganglia were identified in full-thickness biopsies of the ileum and colon by hematoxylin & eosin staining. A1-mm biopsy punch was taken from the paraffin blocks and placed into a Kapton® tube for subsequent tomographic investigation. The samples were scanned, without further preparation, using phase-contrast tomography at two different scales: overview scans (performed with laboratory setups), which allowed localization of the nervous tissue (∼1µm effective voxel size); and high-resolution scans (performed with a synchrotron endstation), which imaged localized regions of 320x320x320 µm3 (176 nm effective voxel size).Results: The contrast allowed us to follow the shape and the size changes of the ganglia, as well as to study their cellular components together with the cells and cellular projections of the periganglional space. Furthermore, it was possible to show the 3D network of the myenteric plexus and to quantify its volume within the samples.Conclusions: Phase-contrast X-ray tomography can be applied for volume analyses of the human ENS and to study tissue components in unstained paraffin-embedded tissue biopsies. This technique could potentially be used to study disease mechanisms, and to compare healthy and diseased tissues in clinical research
Pati-Salam Axion
No full textI discuss the physics case for the GUT axion, motivated by the fact that the GUT axion window could be completely explored by the late phases of the axion Dark Matter experiments CASPEr-Electric and ABRACADABRA. This connection is exemplified for the case of the Pati-Salam partial unification scheme, in which the axion mass is predicted as a function of a sliding Left-Right symmetry breaking scale
Evidence for Higgs boson decay to a pair of muons
No full textEvidence for Higgs boson decay to a pair of muons is presented. This result combines searches in four exclusive categories targeting the production of the Higgs boson via gluon fusion, via vector boson fusion, in association with a vector boson, and in association with a top quark-antiquark pair. The analysis is performed using proton-proton collision data at 13 TeV, corresponding to an integrated luminosity of 137 fb, recorded by the CMS experiment at the CERN LHC. An excess of events over the background expectation is observed in data with a significance of 3.0 standard deviations, where the expectation for the standard model (SM) Higgs boson with mass of 125.38 GeV is 2.5. The combination of this result with that from data recorded at 7 and 8 TeV, corresponding to integrated luminosities of 5.1 and 19.7 fb, respectively, increases both the expected and observed significances by 1%. The measured signal strength, relative to the SM prediction, is 1.19 (stat) (syst). This result constitutes the first evidence for the decay of the Higgs boson to second generation fermions and is the most precise measurement of the Higgs boson coupling to muons reported to date
SASBDB: Towards an automatically curated and validated repository for biological scattering data
No full textSmall‐angle scattering (SAS) of X‐rays and neutrons is a fundamental tool to study the nanostructural properties, and in particular, biological macromolecules in solution. In structural biology, SAS recently transformed from a specialization into a general technique leading to a dramatic increase in the number of publications reporting structural models. The growing amount of data recorded and published has led to an urgent need for a global SAS repository that includes both primary data and models. In response to this, a small‐angle scattering biological data bank (SASBDB) was designed in 2014 and is available for public access at www.sasbdb.org. SASBDB is a comprehensive, free and searchable repository of SAS experimental data and models deposited together with the relevant experimental conditions, sample details and instrument characteristics. SASBDB is rapidly growing, and presently has over 1,000 entries containing more than 1,600 models. We describe here the overall organization and procedures of SASBDB paying most attention to user‐relevant information during submission. Perspectives of further developments, in particular, with OneDep system of the Protein Data Bank, and also widening of SASBDB including new types of data/models are discussed
X-ray Zernike phase contrast tomography: 3D ROI visualization of mm-sized mice organ tissues down to sub-cellular components
No full textThanks to its non-invasive nature, X-ray phase contrast tomography is a very versatile imaging tool for biomedical studies. In contrast, histology is a well-established method, though having its limitations: it requires extensive sample preparation and it is quite time consuming. Therefore, the development of nano-imaging techniques for studying anatomic details at the cellular level is gaining more and more importance. In this article, full field transmission X-ray nanotomography is used in combination with Zernike phase contrast to image millimeter sized unstained tissue samples at high spatial resolution. The regions of interest (ROI) scans of different tissues were obtained from mouse kidney, spleen and mammalian carcinoma. Thanks to the relatively large field of view and effective pixel sizes down to 36 nm, this 3D approach enabled the visualization of the specific morphology of each tissue type without staining or complex sample preparation. As a proof of concept technique, we show that the high-quality images even permitted the 3D segmentation of multiple structures down to a sub-cellular level. Using stitching techniques, volumes larger than the field of view are accessible. This method can lead to a deeper understanding of the organs’ nano-anatomy, filling the resolution gap between histology and transmission electron microscopy
Mechanism of low temperature deformation in aluminium alloys
No full textThis study investigates differences in the deformation mechanisms between room temperature (296 K) and cryogenic temperatures (77 K) and their advantages for low temperature formability in alloys EN AW 1085, EN AW 5182 and EN AW 6016. Compared to room temperature behaviour, tensile tests showed an overall increase in yield strength, ultimate tensile strength and uniform elongation with differences among the principal alloy types. In general, the improved mechanical properties result from higher strain hardening rates at lower temperatures. The application of an extended Kocks-Mecking approach showed a significant reduction of the dynamic recovery and suggested higher dislocation densities upon cryogenic deformation. This was confirmed via in-situ synchrotron experiments, which also reveal a higher proportion of screw dislocations. Moreover, kernel average misorientation maps from electron backscattered diffraction and in-situ cryogenic deformation in a transmission electron microscope displayed a more uniform dislocation arrangement with a reduction of slip lines and less highly misaligned areas after deformation at lower temperatures. Supported by a detailed characterization of the microstructure and its dislocation structure, the associated fundamental mechanisms we reveal, which are at the origin of the exceptional improvement in mechanical properties, are extensively discussed