DYW domain structures imply an unusual regulation principle in plant organellar RNA editing catalysis

RNA editosomes selectively deaminate cytidines to uridines in plant organellar transcripts mostly to restore protein functionality and consequently facilitate mitochondrial and chloroplast function. The RNA editosomal pentatricopeptide repeat proteins serve target RNA recognition, whereas the intensively studied DYW domain elicits catalysis. Here we present structures and functional data of a DYW domain in an inactive ground state and activated. DYW domains harbour a cytidine deaminase fold and a C terminal DYW motif, with catalytic and structural zinc atoms, respectively. A conserved gating domain within the deaminase fold regulates the active site sterically and mechanistically in a process that we termed gated zinc shutter. Based on the structures, an autoinhibited ground state and its activation are cross validated by RNA editing assays and differential scanning fluorimetry. We anticipate that, in vivo, the framework of an active plant RNA editosome triggers the release of DYW autoinhibition to ensure a controlled and coordinated cytidine deamination playing a key role in mitochondrial and chloroplast homeostasi

Detection and effects of lack of fusion defects in Hastelloy X manufactured by laser powder bed fusion

Laser Powder Bed Fusion (L-PBF) is increasingly used for the manufacturing of complex metal parts. A major hurdle for L-PBF to manufacture critical parts is the lack of knowledge about the effects of inner material defects on the material properties. This paper presents a new method to manufacture specimens with inner lack of fusion (LOF) defects and to detect and localize them simultaneously by the in-process monitoring tool Optical Tomography (OT). The presence of defects at locations indicated by OT was verified through Computed Tomography analyses. Correlative metallographic preparation of the processed specimens showed LOF defects with their main extent within the build plane and sharp edges. Moreover, microstructural investigations revealed a fine globular grain structure and coarse dendritic segregations in the area, influenced by the defect. Correlations between the LOF defects analyzed in the microstructure and corresponding OT indications were established. Tensile tests and high cycle fatigue tests were performed on defective and non-defective material to evaluate the effects of LOF defects on the material properties of Hastelloy® X manufactured by L-PBF. While a minor influence of the LOF defects on static material properties was identified, the fatigue life of the defective specimens was significantly reduced

Water Induced and Wavelength Dependent Light Absorption and Emission Dynamics in Triple Cation Halide Perovskites

Metal halide perovskites MHP can be made more stable through the addition of small amounts of cesium. Despite the improvement, these multication absorbers still display strong environmental sensitivity to any combination of factors, including water, oxygen, bias, temperature, and light. Here, the relationship is elucidated between light absorption, charge carrier radiative recombination, and relative humidity rH for the Cs0.05FA0.79MA0.16Pb I0.83Br0.17 3 composition, revealing partially reversible reductions in the extinction coefficient and fully reversible 25 enhancements in absolute light emission registered across the same humidity cycles up to 70 rH. With in situ excitation wavelength dependent measurements, irreversible changes are identified in the perovskite after a single cycle of humidity dependent photoluminescence PL performed with 450 nm excitation. The in situ measurement platform can be extended to test the effect of other stressors on thin films optical behavio

S4(13)-PV cell-penetrating peptide induces physical and morphological changes in membrane-mimetic lipid systems and cell membranes: Implications for cell internalization

The present work aims to gain insights into the role of peptide–lipid interactions in the mechanisms of cellular internalization and endosomal escape of the S4(13)-PV cell-penetrating peptide, which has been successfully used in our laboratory as a nucleic acid delivery system. A S4(13)-PV analogue, S4(13)-PVscr, displaying a scrambled amino acid sequence, deficient cell internalization and drug delivery inability, was used in this study for comparative purposes. Differential scanning calorimetry, fluorescence polarization and X-ray diffraction at small and wide angles techniques showed that both peptides interacted with anionic membranes composed of phosphatidylglycerol or a mixture of this lipid with phosphatidylethanolamine, increasing the lipid order, shifting the phase transition to higher temperatures and raising the correlation length between the bilayers. However, S4(13)-PVscr, in contrast to the wild-type peptide, did not promote lipid domain segregation and induced the formation of an inverted hexagonal lipid phase instead of a cubic phase in the lipid systems assayed. Electron microscopy showed that, as opposed to S4(13)-PVscr, the wild-type peptide induced the formation of a non-lamellar organization in membranes of HeLa cells. We concluded that lateral phase separation and destabilization of membrane lamellar structure without compromising membrane integrity are on the basis of the lipid-driven and receptor-independent mechanism of cell entry of S4(13)-PV peptide. Overall, our results can contribute to a better understanding of the role of peptide–lipid interactions in the mechanisms of cell-penetrating peptide membrane translocation, helping in the future design of more efficient cell-penetrating peptide-based drug delivery systems