Retaining the structural integrity of disulfide bonds in diphtheria toxoid carrier protein is crucial for the effectiveness of glycoconjugate vaccine candidates

The introduction of glycoconjugate vaccines marks an important point in the fight against various infectious diseases. The covalent conjugation of relevant polysaccharide antigens to immunogenic carrier proteins enables the induction of a long-lasting and robust IgG antibody response, which is not observed for pure polysaccharide vaccines. Although there has been remarkable progress in the development of glycoconjugate vaccines, many crucial parameters remain poorly understood. In particular, the influence of the conjugation site and strategy on the immunogenic properties of the final glycoconjugate vaccine is the focus of intense research. Here, we present a comparison of two cysteine selective conjugation strategies, elucidating the impact of both modifications on the structural integrity of the carrier protein, as well as on the immunogenic properties of the resulting glycoconjugate vaccine candidates. Our work suggests that conjugation chemistries impairing structurally relevant elements of the protein carrier, such as disulfide bonds, can have a dramatic effect on protein immunogenicity.

The introduction of glycoconjugate vaccines marks an important point in the fight against various infectious diseases.     

Preparation and optical characterization of two photoactive poly(bisphenol a ethoxylate diacrylate) copolymers containing designed amino‐nitro‐substituted azobenzene units,obtained via classical and frontal polymerization,using novel ionic liquids as initiators

The frontal polymerization (FP) of bisphenol A ethoxylate diacrylate (BPAEDA) was carried with and without the presence of two different azobenzene comonomers by means of an external heating source. The first azomonomer (MDR‐1) is a derivative of disperse red‐1, N‐ethyl‐N‐(2‐hydroxyethyl)‐4‐(4‐nitrophenylazo)aniline, whereas the second (E)‐2‐(4‐((4‐nitrophenyl)diazenyl)phenyl)‐5,8,11‐trioxa‐2‐azatridecan‐13‐yl methacrylate (4PEGMAN) comes from the azo‐dye N‐methyl‐N‐{4‐[(E)‐(4‐nitrophenyl)diazenyl]phenyl}‐N‐(11‐hydroxy‐3,6,9‐trioxaundecas‐1‐yl) amine. In this work, an ionic liquid trihexyltetradecylphosphonium persulfate was used as initiator. This compound produced stable propagating polymerization fronts with good velocities and moderate maximum temperature values. Moreover, this initiator prevented bubble formation and was found to be the most efficient when it was used in lower amounts with respect to other initiators, such as benzoyl peroxide, 2,2′‐azobisisobutyronitrile, aliquat persulfate®, and tetrabutylphosphonium persulfate. The thermal properties of the obtained polymers and copolymers were determined by thermogravimetric analysis and differential scanning calorimetry. The nonlinear optical (NLO) characterizations of the developed BPAEDA/MDR‐1 and BPAEDA/4PEGMAN copolymers were performed according to the Z‐Scan technique in film samples prepared by classical polymerization. It has been proven that samples with higher 4PEGMAN content (0.26 mol %) exhibited outstanding cubic NLO‐activity with positive NLO‐refractive coefficients in the promising range of n₂ = +3.2 × 10^?4 esu. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

A paradigmatic system to study the transition from zero/Hopf to double-zero/Hopf bifurcation

A two-d.o.f.?system experiencing codimension-three double-zero/Hopf bifurcation is considered. This is a special bifurcation which simultaneously involves a defective and a nondefective pair of critical eigenvalues, therefore, requiring a perturbation method specifically tailored on it. A nonstandard version of the multiple scale method is implemented, in which fractional power expansions, both for state-variables and time are used, and high-order arbitrary amplitudes are introduced. Bifurcation equations are obtained, governing the slow flow on the center manifold, which turns out to be tangent to the space spanned by the four critical eigenvectors. These are used to analyze the transition from codimension-three to codimension-two single-zero/Hopf bifurcations, occurring when the modulus of the damping is increased from small to order-one values. Bifurcation charts are obtained, displaying the role of quasi-periodic motions in the transition.     

Predicting the UV spectrum of polyoxometalates by TD‐DFT

UV absorption spectra of the Lindqvist polyoxometalate [W₆O₁₉]^2? were predicted by relativistic time‐dependent density functional theory with several combinations of density functional and basis set. Hybrid functionals with frozen‐core Slater basis sets were found to provide the best agreement with experiment while keeping reasonable computational demand. The approach was extended to [W₁₀O₃₂]^4? and [PW₁₂O₄₀]^3?, suggesting that it can be applied to the polyoxometalates family. © 2011 Wiley Periodicals, Inc. J Comput Chem, 2011     

Synthesis and characterization of poly(ethylene glycol) diacrylate copolymers containing azobenzene groups prepared by frontal polymerization

A novel polymer matrix containing amino–nitro substituted azobenzene groups was obtained by frontal polymerization. (E)‐2‐(Ethyl(4‐((4‐nitrophenyl)diazenyl)phenyl)amino)ethyl methacrylate (MDR‐1) was copolymerized with poly(ethylene glycol) diacrylate (PEGDA) using this easy and fast polymerization technique. The effect of the amount of the incorporated azo‐monomer into the polymer matrix was studied in detail and correlated to front velocity, maximum temperature, initiator concentration, and monomer conversion. The obtained materials were characterized by infrared spectroscopy (Fourier transform infrared), and their thermal properties were studied by thermogravimetric analysis and differential scanning calorimetry. Moreover, the optical properties of the polymers were studied by absorption spectroscopy in the UV–Vis region. Absorption spectra of the copolymers exhibit a significant blue shift of the absorption bands with respect to the azo‐monomer, due to the presence of H‐aggregates. Cubic nonlinear optical (NLO) characterizations of the PEGDA/MDR‐1 copolymers were performed according to the Z‐Scan technique. It has been proven that samples with higher MDR‐1 content (0.75 mol %) exhibited outstandingly high NLO‐activity with negative NLO‐refractive coefficients in the promising range of n₂ = ?8.057 × 10^?4 esu. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Turbulent boundary layer separation control and loss evaluation of low profile vortex generators

The present paper analyses the results of a detailed experimental study on low profile vortex generators used to control the turbulent boundary layer separation on a large-scale flat plate with a prescribed adverse pressure gradient, typical of aggressive turbine intermediate ducts. This activity is part of a joint European research program on Aggressive Intermediate Duct Aerodynamics (AIDA). Laser Doppler Velocimetry and a Kiel total pressure probe have been employed to perform measurements in the test section symmetry plane and in cross-stream planes to investigate the turbulent boundary layer, with and without control device application.Velocity fields, Reynolds stresses, and total pressure distributions are analysed and compared for the controlled and non controlled flow conditions to characterize the mean flow behaviour. The detail and the accuracy of the measurements allow the evaluation of the deformation works of the mean motion in the test section symmetry plane. Normal and shear contributions of viscous and turbulent deformation works have been analysed and employed to explain the distribution of the total pressure loss. For the controlled flow the discussion of the flow field is extended considering the effects of the vortex generated in the cross-stream planes. The experimental data allow the evaluation of the global amount of losses, considering a balance of total pressure fluxes in the different measuring planes.     

The effect of point mutations on copper(II) complexes with peptide fragments encompassing the 106–114 region of human prion protein

Abstract  

The tetrapeptides Ac-SKHM-NH₂, Ac-TKHM-NH₂, Ac-MKHS-NH₂, Ac-S(OMe)KHM-NH₂, and Ac-MKHS(OMe)-NH₂ and the nonapeptides Ac-KTNSKHMAG-NH₂ and Ac-KTNMKHSAG-NH₂ were synthesized and their copper(II) complexes were studied by potentiometric, UV–Vis, circular dichroism (CD), and electron paramagnetic resonance (EPR) spectroscopic methods. These peptides mimic the 109–112 and 106–114 residues of the sequence of human prion protein. The imidazole-N donor atoms of histidyl residues were found to be the primary metal binding sites of all peptide fragments. This binding mode provides a good possibility for the cooperative deprotonation and metal ion coordination of two amide functions preceding histidine. The (N_im,N⁻,N⁻)-bonded species predominate in the pH range 5.5–7.0 and the free coordination sites of these species make possible the metal binding of weakly coordinating side chains. The comparison of the potentiometric and spectroscopic results revealed the stabilizing role of the oxygen donors of seryl, threonyl, or methoxyseryl residues of Ac-SKHM-NH₂, Ac-TKHM-NH₂, Ac-S(OMe)KHM-NH₂, and Ac-KTNSKHMAG-NH₂ containing the mutations in position 109. These interactions were, however, not observed in the peptides containing the specific amino acids in other locations of the peptide sequence.