The molecular basis of regulation of bacterial capsule assembly by Wzc

Bacterial extracellular polysaccharides (EPSs) play critical roles in virulence. Many bacteria assemble EPSs via a multi-protein “Wzx-Wzy” system, involving glycan polymerization at the outer face of the cytoplasmic/inner membrane. Gram-negative species couple polymerization with translocation across the periplasm and outer membrane and the master regulator of the system is the tyrosine autokinase, Wzc. This near atomic cryo-EM structure of dephosphorylated Wzc from E. coli shows an octameric assembly with a large central cavity formed by transmembrane helices. The tyrosine autokinase domain forms the cytoplasm region, while the periplasmic region contains small folded motifs and helical bundles. The helical bundles are essential for function, most likely through interaction with the outer membrane translocon, Wza. Autophosphorylation of the tyrosine-rich C-terminus of Wzc results in disassembly of the octamer into multiply phosphorylated monomers. We propose that the cycling between phosphorylated monomer and dephosphorylated octamer regulates glycan polymerization and translocation.

Structures of soluble rabbit neprilysin complexed with phosphoramidon or thiorphan

Neutral endopeptidase (neprilysin; NEP) is a proteinase that cleaves a wide variety of peptides and has been implicated in Alzheimer's disease, cardiovascular conditions, arthritis and other inflammatory diseases. The structure of the soluble extracellular domain (residues 55–750) of rabbit neprilysin was solved both in its native form at 2.1 Å resolution, and bound to the inhibitors phosphoramidon and thiorphan at 2.8 and 3.0 Å resolution, respectively. Consistent with the extracellular domain of human neprilysin, the structure reveals a large central cavity which contains the active site and the location for inhibitor binding.

A Methylcellulose Hydrogel as Support for 3D Plotting of Complex Shaped Calcium Phosphate Scaffolds

3D plotting is an additive manufacturing technology enabling biofabrication, thus the integration of cells or biologically sensitive proteins or growth factors into the manufacturing process. However, most (bio-)inks developed for 3D plotting were not shown to be processed into clinically relevant geometries comprising critical overhangs and cavities, which would collapse without a sufficient support material. Herein, we have developed a support hydrogel ink based on methylcellulose (mc), which is able to act as support as long as the co-plotted main structure is not stable. Therefore, 6 w/v %, 8 w/v % and 10 w/v % mc were allowed to swell in water, resulting in viscous inks, which were characterized for their rheological and extrusion properties. The successful usage of 10 w/v % mc as support ink was proven by multichannel plotting of the support together with a plottable calcium phosphate cement (CPC) acting as main structure. CPC scaffolds displaying critical overhangs or a large central cavity could be plotted accurately with the newly developed mc support ink. The dissolution properties of mc allowed complete removal of the gel without residuals, once CPC setting was finished. Finally, we fabricated a scaphoid bone model by computed tomography data acquisition and co-extrusion of CPC and the mc support hydrogel.

A Methylcellulose Hydrogel as Support for 3D Plotting of Complex Shaped Calcium Phosphate Scaffolds

3D plotting is an additive manufacturing technology enabling biofabrication, thus the integration of cells or biologically sensitive proteins or growth factors into the manufacturing process. However, most (bio-)inks developed for 3D plotting were not shown to be processed into clinical relevant geometries comprising critical overhangs and cavities, which would collapse without a sufficient support material. Herein, we have developed a support hydrogel ink based on methylcellulose (mc), which is able to act as support as long as the co-plotted main structure is not stable. Therefore, 6 w/v %, 8 w/v % and 10 w/v % mc were allowed to swell in water, resulting in viscous inks, which were characterized for their rheological and extrusion properties. The successful usage of 10 w/v % mc as support ink was proven by multichannel plotting of the support together with a plottable calcium phosphate cement (CPC) acting as main structure. CPC scaffolds displaying critical overhangs or a large central cavity could be plotted accurately with the newly developed mc support ink. The dissolution properties of mc allowed complete removal of the gel without residuals, once CPC setting was finished. Finally, we fabricated a scaphoid bone model by computed tomography data acquisition and co-extrusion of CPC and the mc support hydrogel.

Solution and solid-state characterization of a dicopper receptor for large substrates

Ligand 2 contains two metal-binding domains separated by a rigid spacer and assembles into a dicopper receptor with a large central cavity with no evidence of catenation.Key words: copper complex, coordination, X-ray crystallography, molecular recognition.

In vitro effects of Trichinella spiralis on muscle cells

Introduction of excretory/secretory (ES) products of both infective-stage and newborn larvae of Trichinella spiralis into cultures of primary rat myocytes elicited morphological and structural changes in the myotubes. They appeared more granular, thinner, and failed to form networks. The most prominent lesion was the formation of ‘nodular’ structures, each bearing an enlarged nucleus, along the myotubes. Each node contained numerous cavities enclosed by an intact sarcolemma. Co-culture of myocytes with newborn larvae also elicited nodular formation but each node contained a large central cavity encircled by smaller ones. An immunocytolocalization study using IFAT and laser confocal microscopy showed the presence of parasitic epitopes inside the nodes. However, ES products from adult worms did not affect the myotubes.