Chemical Synthesis and Immunological Evaluation of a Pentasaccharide Bearing Multiple Rare Sugars as a Potential Anti-pertussis Vaccine

With the infection rate of Bordetella pertussis at a 60-year high, there is an urgent need for new anti-pertussis vaccines. The lipopolysaccharide (LPS) of B. pertussis is an attractive antigen for vaccine development. With the presence of multiple rare sugars and unusual glycosyl linkages, the B. pertussis LPS is a highly challenging synthetic target. In this work, aided by molecular dynamics simulation and modeling, a pertussis-LPS-like pentasaccharide was chemically synthesized for the first time. The pentasaccharide was conjugated with a powerful carrier, bacteriophage Qβ, as a vaccine candidate. Immunization of mice with the conjugate induced robust anti-glycan IgG responses with IgG titers reaching several million enzyme-linked immunosorbent assay (ELISA) units. The antibodies generated were long lasting and boostable and could recognize multiple clinical strains of B. pertussis, highlighting the potential of Qβ-glycan as a new anti-pertussis vaccine.     

On the Stability of Pt-Based Catalysts in HBr/Br2 Solution

Stability studies on supported metal nanoparticles are essential for gaining insight into the design and optimization of high-performance materials. In this work, the dissolutions of Pt-based catalysts in HBr/Br₂ mixture of various concentration regimes were studied and correlated with material structural properties. The dissolution of metal nanoparticles was enhanced by adding Br₂ to the HBr solution. Comparing with commercial Pt/C catalyst, the well-alloyed PtIr/C catalyst was observed to exhibit high resistance towards dissolution. In addition, regulating the accessibility of the metal sites to dissolution-inducing species contributed to the marked stability of the nanoparticles in HBr/Br₂ solutions, as shown for the surface-modified PtIr/C catalysts with organic diamine molecules.     

Symmetry calculation for molecules and transition states

The symmetry of molecules and transition states of elementary reactions is an essential property with important implications for computational chemistry. The automated identification of symmetry by computers is a very useful tool for many applications, but often relies on the availability of three‐dimensional coordinates of the atoms in the molecule and hence becomes less useful when these coordinates are a priori unavailable. This article presents a new algorithm that identifies symmetry of molecules and transition states based on an augmented graph representation of the corresponding structures, in which both topology and the presence of stereocenters are accounted for. The automorphism group order of the graph associated with the molecule or transition state is used as a starting point. A novel concept of label‐stereoisomers, that is, stereoisomers that arise after labeling homomorph substituents in the original molecule so that they become distinguishable, is introduced and used to obtain the symmetry number. The algorithm is characterized by its generic nature and avoids the use of heuristic rules that would limit the applicability. The calculated symmetry numbers are in agreement with expected values for a large and diverse set of structures, ranging from asymmetric, small molecules such as fluorochlorobromomethane to highly symmetric structures found in drug discovery assays. The new algorithm opens up new possibilities for the fast screening of the degree of symmetry of large sets of molecules. © 2014 Wiley Periodicals, Inc.     

Structure Elucidation and Activity of Kolossin A,the D‐/L‐Pentadecapeptide Product of a Giant Nonribosomal Peptide Synthetase

The largest continuous bacterial nonribosomal peptide synthetase discovered so far is described. It consists of 15 consecutive modules arising from an uninterrupted, fully functional gene in the entomopathogenic bacterium Photorhabdus luminescens. The identification of its cryptic biosynthesis product was achieved by using a combination of genome analysis, promoter exchange, isotopic labeling experiments, and total synthesis of a focused collection of peptide candidates. Although it belongs to the growing class of D ‐/ L ‐peptide natural products, the encoded metabolite kolossin A was found to be largely devoid of antibiotic activity and is likely involved in interspecies communication. A stereoisomer of this peculiar natural product displayed high activity against Trypanosoma brucei rhodesiense, a recalcitrant parasite that causes the deadly disease African sleeping sickness.     

Scalable bottom‐up assembly of suspended carbon nanotube and graphene devices by dielectrophoresis

Bottom‐up assembly by dielectrophoresis (DEP) has emerged in recent years as a viable alternative to conventional top–down fabrication of electronic devices from nanomaterials, particularly carbon nanotubes and graphene. Here, we demonstrate how this technique can be extended to fabricate devices containing carbon nanotubes and graphene suspended between two electrodes over a back‐gate electrode. The suspended device geometry is critical for the development of nano‐electromechanical devices and to extract maximum performance out of electronic and optoelectronic devices. This technique allows for parallel assembly of devices over large scale. (© 2015 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)     

Synthesis and characterisation of low density porous polymers by reversible addition-fragmentation chain transfer (RAFT)

PolyHIPE foams with densities of 0.05–0.1 g cm^?3 have been prepared by the polymerisation of the continuous phase of high internal phase emulsions (HIPEs). The internal aqueous phase in HIPE occupies more than 74 % of the total volume, which leads to highly porous and open-cell morphologies. In this paper a method of preparing polyHIPE foams by using reversible addition-fragmentation chain transfer (RAFT) polymerisation has been investigated. Polystyrene-co-polymethyl methacrylate (PS-co-PMMA) has been studied and by using a variety of characterisation methods, it was possible to compare the polyHIPEs prepared by the conventional free radical polymerisation (FRP) to those by RAFT polymerisation. Scanning electron microscopy images have confirmed the presence of a cellular polyHIPE structure. PS-co-PMMA polyHIPEs made by RAFT have significantly narrower molecular weight distribution with values for the polydispersity index (PDI) for PS-co-PMMA between 1.46 and 2.08 compared to 4.68 observed by FRP. The effects of different concentrations of the RAFT agent on structure, glass transition temperature (T _g) and PDI of PS-co-PMMA polyHIPE foams are presented.