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An integrated experimental and Large-Eddy Simulation (LES) study is presented for homogeneous premixed combustion in a spark-ignition engine. The engine is a single-cylinder two-valve optical research engine with transparent liner and piston: the Transparent Combustion Chamber (TCC) engine. This is a relatively simple, open engine configuration that can be used for LES model development and validation by other research groups. Pressure-based combustion analysis, optical diagnostics and LES have been combined to generate new physical insight into the early stages of combustion. The emphasis has been on developing strategies for making quantitative comparisons between high-speed/high-resolution optical diagnostics and LES using common metrics for both the experiments and the simulations, and focusing on the important early flame development period. Results from two different LES turbulent combustion models are presented, using the same numerical methods and computational mesh. Both models yield Cycle-to-Cycle Variations (CCV) in combustion that are higher than what is observed in the experiments. The results reveal strengths and limitations of the experimental diagnostics and the LES models, and suggest directions for future diagnostic and simulation efforts. In particular, it has been observed that flame development between the times corresponding to the laminar-to-turbulent transition and 1% mass-burned fraction are especially important in establishing the subsequent combustion event for each cycle. This suggests a range of temporal and spatial scales over which future experimental and simulation efforts should focus.

S-layers are crystalline arrays found on bacterial and archaeal cells. Lactobacillus is a diverse family of bacteria known especially for potential gut health benefits. This study focuses on the S-layer proteins from Lactobacillus acidophilus and Lactobacillus amylovorus common in the mammalian gut. Atomic resolution structures of Lactobacillus S-layer proteins SlpA and SlpX exhibit domain swapping, and the obtained assembly model of the main S-layer protein SlpA aligns well with prior electron microscopy and mutagenesis data. The S-layer's pore size suggests a protective role, with charged areas aiding adhesion. A highly similar domain organization and interaction network are observed across the Lactobacillus genus. Interaction studies revealed conserved binding areas specific for attachment to teichoic acids. The structure of the SlpA S-layer and the suggested incorporation of SlpX as well as its interaction with teichoic acids lay the foundation for deciphering its role in immune responses and for developing effective treatments for a variety of infectious and bacteria-mediated inflammation processes, opening opportunities for targeted engineering of the S-layer or lactobacilli bacteria in general., Competing Interests: Competing interests statement:The authors declare no competing interest.

Wall teichoic acids (WTAs) are glycopolymers decorating the surface of Gram-positive bacteria and potential targets for antibody-mediated treatments against Staphylococcus aureus , including methicillin-resistant (MRSA) strains. Through a combination of glycan microarray, synthetic chemistry, crystallography, NMR, and computational studies, we unraveled the molecular and structural details of fully defined synthetic WTA fragments recognized by previously described monoclonal antibodies (mAbs 4461 and 4497). Our results unveiled the structural requirements for the discriminatory recognition of α- and β-GlcNAc-modified WTA glycoforms by the complementarity-determining regions (CDRs) of the heavy and light chains of the mAbs. Both mAbs interacted not only with the sugar moiety but also with the phosphate groups as well as residues in the ribitol phosphate (RboP) units of the WTA backbone, highlighting their significant role in ligand specificity. Using elongated WTA fragments, containing two sugar modifications, we also demonstrated that the internal carbohydrate moiety of α-GlcNAc-modified WTA is preferentially accommodated in the binding pocket of mAb 4461 with respect to the terminal moiety. Our results also explained the recently documented cross-reactivity of mAb 4497 for β-1,3/β-1,4-GlcNAc-modified WTA, revealing that the flexibility of the RboP backbone is crucial to allow positioning of both glycans in the antibody binding pocket., Competing Interests: The authors declare no competing financial interest., (© 2022 The Authors. Published by American Chemical Society.)

Lipoteichoic acids (LTAs) have been addressed as possible antigen candidates for vaccine development against several opportunistic Gram-positive pathogens. The study of structure-immunogenicity relationship represents a challenge due to the heterogenicity of LTA extracted from native sources. LTAs are built up from glycerol phosphate (GroP) repeating units and they can be substituted at the C-2-OH with carbohydrate appendages or d-alanine residues. The substitution pattern, but also the absolute chirality of the GroP residues can impact the interaction with chiral biomolecules including antibodies and biosynthesis enzymes. We have generated a set of diastereomeric GroP hexamers bearing a glucosyl modification at one of the residues. The chirality of the glycerol building block had an important impact on the stereoselectivity of the glycosylation reaction between the glycosyl donor and the glycerol C-2-OH acceptor. The GroP C-2-chirality also played an important role in the interaction with TA recognizing antibodies. These findings have important implications for the design and synthesis of synthetic TA fragments for diagnostic and therapeutic applications., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)