Single validation of CE method for determining free polysaccharide content in a Brazilian meningococcal C conjugate vaccine

Neisseria meningitidis group C is an encapsulated bacterium that causes several diseases and is associated with high mortality rates, thereby constituting a serious public health problem. Bio‐Manguinhos/Fiocruz is developing a conjugate vaccine by covalent attachment of capsular polysaccharide to hydrazide‐activated tetanus toxoid through reductive amination. It is necessary to quantify free components as a quality control process to prevent exacerbated adverse reactions and/or attenuation of vaccine immunogenicity. Thus, this study aimed to develop and validate a quality control method appropriate for the separation and quantification of free polysaccharide present in this conjugate N. meningitidis group C vaccine using CE. CZE was used to remove unbound polysaccharide, and the electrophoretic conditions were varied to optimize resolution. We were able to develop and validate the proposed method, which was linear and showed a matrix effect. Repeatability and partial reproducibility of the method were also evaluated. The robustness results showed that control of temperature is required for reliable results. The validated method will be used to evaluate the conjugate batches submitted for Phase III clinical studies and for routine quality control of the conjugate vaccine.     

Magnetic properties of off-stoichiometric R2Co3Zn14 (R=Y,Gd) single crystals

Single crystal X-ray diffraction data indicate that the R₂Co₃Zn₁₄ (R=Gd, Y) phase crystallizes non-stoichiometrically with a mixed occupancy of Co/Zn atoms on the 12-coordinated transition metal site and one of the three zinc sites. The crystals are rhombohedral with R-3m space group. Magnetization measurements provide no evidence of localized 3d electron moment in Y₂Co_2.3Zn_14.7 which is non-magnetic down to 1.8 K. Thermodynamic and transport measurements on two Gd₂Co_3+xZn_14−x crystals reveal that the extra cobalt influences temperature below which the samples enter into an antiferromagnetic state: T_N=31.5(3) K for Gd₂Co₃Zn₁₄ and 28(1) K for Gd₂Co_4.2Zn_12.8. A lower magnetic ordering temperature of T_mag=6.0(2) K is common in both Gd samples.     

Quantum mechanical studies on model α‐pleated sheets

Pauling and Corey proposed a pleated‐sheet configuration, now called α‐sheet, as one of the protein secondary structures in addition to α‐helix and β‐sheet. Recently, it has been suggested that α‐sheet is a common feature of amyloidogenic intermediates. We have investigated the stability of antiparallel β‐sheet and two conformations of α‐sheet in solution phase using the density functional theoretical method. The peptides are modeled as two‐strand acetyl‐(Ala)₂‐N‐methylamine. Using stages of geometry optimization and single point energy calculation at B3LYP/cc‐pVTZ//B3LYP/6‐31G* level and including zero‐point energies, thermal, and entropic contribution, we have found that β‐sheet is the most stable conformation, while the α‐sheet proposed by Pauling and Corey has 13.6 kcal/mol higher free energy than the β‐sheet. The α‐sheet that resembles the structure observed in molecular dynamics simulations of amyloidogenic proteins at low pH becomes distorted after stages of geometry optimization in solution. Whether the α‐sheets with longer chains would be increasingly favorable in water relative to the increase in internal energy of the chain needs further investigation. Different from the quantum mechanics results, AMBER parm94 force field gives small difference in solution phase energy between α‐sheet and β‐sheet. The predicted amide I IR spectra of α‐sheet shows the main band at higher frequency than β‐sheet. © 2009 Wiley Periodicals, Inc. J Comput Chem, 2010     

Effect of 3d doping on the electronic structure of BaFe2As2

The electronic structure of BaFe(2)As(2) doped with Co, Ni and Cu has been studied by a variety of experimental and theoretical methods, but a clear picture of the dopant 3d states has not yet emerged. Herein we provide experimental evidence of the distribution of Co, Ni and Cu 3d states in the valence band. We conclude that the Co and Ni 3d states provide additional free carriers to the Fermi level, while the Cu 3d states are found at the bottom of the valence band in a localized 3d(10) shell. These findings help shed light on why superconductivity can occur in BaFe(2)As(2) doped with Co and Ni but not Cu.     

Immunocytochemical Analysis of P2X2 in Rat Circumvallate Taste Buds

ABSTRACT: BACKGROUND: Our laboratory has shown that classical synapses and synaptic proteins are associated with Type III cells. Yet it is generally accepted that Type II cells transduce bitter, sweet and umami stimuli. No classical synapses, however, have been found associated with Type II cells. Recent studies indicate that ionotropic purinergic receptors P2X2/P2X3 are present in rodent taste buds. Taste nerve processes express the ionotropic purinergic receptors (P2X2/P2X3). P2X2/P2X3Dbl/ mice are not responsive to sweet, umami and bitter stimuli, and it has been proposed that ATP acts as a neurotransmitter in taste buds. The goal of the present study is to learn more about the nature of purinergic contacts in rat circumvallate taste buds by examining immunoreactivity to antisera directed against the purinergic receptor P2X2. RESULTS: P2X2-like immunoreactivity is present in intragemmal nerve processes in rat circumvallate taste buds. Intense immunoreactivity can also be seen in the subgemmal nerve plexuses located below the basal lamina. The P2X2 immunoreactive nerve processes also display syntaxin-1-LIR. The immunoreactive nerves are in close contact with the IP3R3-LIR Type II cells and syntaxin-1-LIR and/or 5-HT-LIR Type III cells. Taste cell synapses are observed only from Type III taste cells onto P2X2-LIR nerve processes. Unusually large, "atypical" mitochondria in the Type II taste cells are found only at the close appositions with P2X2-LIR nerve processes. P2X2 immunogold particles are concentrated at the membranes of nerve processes at the close appositions with taste cells. CONCLUSIONS: Based on our fluorescence and immunoelectron microscopical studies we believe that both perigemmal and most all intragemmal nerve processes display P2X2-LIR. Moreover, colloidal gold immunoelectron microscopy indicates that P2X2-LIR in nerve processes is concentrated at sites of close apposition with Type II cells. This supports the hypothesis that ATP may be a key neurotransmitter in taste transduction and that Type II cells release ATP, activating P2X2 receptors in nerve processes.     

Atomic resolution and vortex lattice studies of magnetic superconductors: A first approach in the nickel borocarbide TmNi2B2C

We present new scanning tunneling microscopy measurements in the superconductor TmNi₂B₂C. The topography shows in some areas flat surfaces, where atomic size modulations can be identified. We find a hexagonal vortex lattice between 0.15 T and 1.4 T, when the magnetic field is applied along the basal plane of the tetragonal crystal structure (B⊥c)$(B\perp c)$, and a hexagonal to square transition around 0.15 T when the field is applied along the c  -axis (B‖c)$(B\Vert c)$. Measured intervortex distance are smaller than expected at high field, due to the internal field being larger than the applied field.     

Superconductivity in presence of localized magnetic moments. Case study of Er(Ni,Co)2B2C

Some recent results of magnetic and transport measurements on single crystals of the Er(Ni,Co)₂B₂C series will be presented and discussed, in particular, possible evidence of a superzone gap formation at the antiferromagnetic phase transition in pure ErNi₂B₂C, detailed anisotropic H–T phase diagrams and their modification with Co doping, and enhancement of the superconducting critical current in the weak ferromagnetic phase.     

Extractive Fermentation of Xylanase from Aspergillus tamarii URM 4634 in a Bioreactor

Of the many reported applications for xylanase, its use as a food supplement has played an important role for monogastric animals, because it can improve the utilisation of nutrients. The aim of this work was to produce xylanase by extractive fermentation in an aqueous two-phase system using Aspergillus tamarii URM 4634, increasing the scale of production in a bioreactor, partially characterising the xylanase and evaluating its influence on monogastric digestion in vitro. Through extractive fermentation in a bioreactor, xylanase was obtained with an activity of 331.4 U mL^?1 and 72 % yield. The xylanase was stable under variable pH and temperature conditions, and it was optimally active at pH 3.6 and 90 °C. Xylanase activity potentiated the simulation of complete monogastric digestion by 6 %, and only Mg²⁺ inhibited its activity. This process provides a system for efficient xylanase production by A. tamarii URM 4634 that has great potential for industrial use.