SnapShot: Lysine Methylation beyond Histones

Lysine methylation is a prevalent post-translational modification (PTM) used by the cell to reversibly regulate protein function. Although it has been extensively studied in the context of histones and the associated chromatin, the remaining methyllysine proteome remains largely unexplored. This SnapShot provides an overview of the current state of lysine methylation research and its emergence as a dynamic PTM occurring on histone and non-histone proteins. Lysine methylation is a prevalent post-translational modification (PTM) used by the cell to reversibly regulate protein function. Although it has been extensively studied in the context of histones and the associated chromatin, the remaining methyllysine proteome remains largely unexplored. This SnapShot provides an overview of the current state of lysine methylation research and its emergence as a dynamic PTM occurring on histone and non-histone proteins

Dual phase grating interferometer for tunable dark-field sensitivity

Hard X-ray dark-field and phase contrast imaging using grating interferometry have shown great potential for medical and industrial applications. However, the wide spread applicability of the method is challenged by a number of technical related issues such as relatively low dose and flux efficiency due to the absorption grating, fabrication of high quality absorption gratings, slow data acquisition protocol and high mechanical stability requirements. In this paper, the authors propose an interferometric method for dark-field and differential phase contrast imaging based on phase shifting elements only with the purpose to improve the dose and flux efficiency and simplify the setup. The proposed interferometer consists of two identical phase gratings of small pitch (1.3 μm), which generate an interference fringe at the detector plane with a large enough pitch that can be resolved directly. In particular, the system exhibits flexible and tunable dark-field sensitivity which is advantageous to probe unresolvable micro-structure in the sample. Experiments on a micro focal tube validated the method and demonstrated the versatility and tunability of the system compared to conventional Talbot grating interferometer

Circular Unit Cell Gratings for X-ray Dark-Field Imaging

Dark-field imaging has been demonstrated to provide complementary information about the unresolved microstructure of the investigated sample. The usual implementation of a grating interferometer, which can provide access to the dark-field signal, consists of linear gratings limiting the sensitivity to only one direction (perpendicular to the grating lines). Recently, a novel grating design, composed of circular unit cells, was proposed allowing 2D-omnidirectional dark-field sensitivity in a single shot. In this work we present a further optimisation of the proposed grating by changing the arrangement of the unit cells from a Cartesian to a hexagonal grid. We experimentally compare the two designs and demonstrate that the latter has an improved performance

Iterative phase contrast CT reconstruction with novel tomographic operator and data-driven prior

Breast cancer remains the most prevalent malignancy in women in many countries around the world, thus calling for better imaging technologies to improve screening and diagnosis. Grating interferometry (GI)-based phase contrast X-ray CT is a promising technique which could make the transition to clinical practice and improve breast cancer diagnosis by combining the high three-dimensional resolution of conventional CT with higher soft-tissue contrast. Unfortunately though, obtaining high-quality images is challenging. Grating fabrication defects and photon starvation lead to high noise amplitudes in the measured data. Moreover, the highly ill-conditioned differential nature of the GI-CT forward operator renders the inversion from corrupted data even more cumbersome. In this paper, we propose a novel regularized iterative reconstruction algorithm with an improved tomographic operator and a powerful data-driven regularizer to tackle this challenging inverse problem. Our algorithm combines the L-BFGS optimization scheme with a data-driven prior parameterized by a deep neural network. Importantly, we propose a novel regularization strategy to ensure that the trained network is non-expansive, which is critical for the convergence and stability analysis we provide. We empirically show that the proposed method achieves high quality images, both on simulated data as well as on real measurements

Genotypic and Environmental Effects on the Volatile Chemotype of Valeriana jatamansi Jones

Valeriana jatamansi Jones is an aromatic medicinal herb and important alternative to V. officinalis, which is utilized for medicinal purposes in China and India and also as spices in India. Bioactive ingredients of V. jatamansi vary in different regions. However, no information is currently available on influence of genotype and environmental factors in the volatile compounds, especially when germplasms and planting locations need to be selected. Based on the results of SNP and volatile constituents from GC-MS analysis, this study found various genotypes and chemotypes of V. jatamansi for wild plants from seven regions in China and common-garden samples; correlations between genotype and chemotype were revealed for the plants. Two distinct populations (PX, FY) were distinguishable from five others (GJ, YL, SY, DD, DY) according to their genotypes and volatile profiles, the consistency of which was observed showing that genotype could significantly influence chemotype. Wild populations and common-garden samples were also separated in their volatile profiles, demonstrating that environmental factors strongly affected their chemotypes. Compounds contributing to the discrimination were identified as discriminatory compounds. This investigation has explored and provided essential information concerning the correlation between genotype and chemotype as well as environmental factors and chemotype of V. jatamansi in some regions of China. Feasible plantation and conservation strategies of V. jatamansi could be further explored based on these results