Enzymatic Oxygen Microsensor Based on Bilirubin Oxidase Applied to Microbial Fuel Cells Analysis

A selective oxygen biosensor based on bilirubin oxidase (BOx) was developed. The sensor was used for determining oxygen profiles in a membraneless, single‐chamber microbial fuel cell (SCMFC), fed with raw wastewater. The linear response of the sensor was optimized by a diffusion layer of silica gel. A computer‐controlled stage was used to obtain accurate and precise measurements. Oxygen concentration in biofilms covering electrodes was measured, showing 3 mg L^?1 of O₂ in the bulk solution, decreasing to 0 mg L^?1 in the cathodic biofilm. The MFC generated power in the range of 0–0.08 mW, associated to the oxygen content.     

Evaluation of diverse α/β-backbone patterns for functional α-helix mimicry: analogues of the Bim BH3 domain

Peptidic oligomers that contain both α- and β-amino acid residues, in regular patterns throughout the backbone, are emerging as structural mimics of α-helix-forming conventional peptides (composed exclusively of α-amino acid residues). Here we describe a comprehensive evaluation of diverse α/β-peptide homologues of the Bim BH3 domain in terms of their ability to bind to the BH3-recognition sites on two partner proteins, Bcl-x(L) and Mcl-1. These proteins are members of the anti-apoptotic Bcl-2 family, and both bind tightly to the Bim BH3 domain itself. All α/β-peptide homologues retain the side-chain sequence of the Bim BH3 domain, but each homologue contains periodic α-residue → β(3)-residue substitutions. Previous work has shown that the ααβαααβ pattern, which aligns the β(3)-residues in a 'stripe' along one side of the helix, can support functional α-helix mimicry, and the results reported here strengthen this conclusion. The present study provides the first evaluation of functional mimicry by ααβ and αααβ patterns, which cause the β(3)-residues to spiral around the helix periphery. We find that the αααβ pattern can support effective mimicry of the Bim BH3 domain, as manifested by the crystal structure of an α/β-peptide bound to Bcl-x(L), affinity for a variety of Bcl-2 family proteins, and induction of apoptotic signaling in mouse embryonic fibroblast extracts. The best αααβ homologue shows substantial protection from proteolytic degradation relative to the Bim BH3 α-peptide.     

Kapellasite: a kagome quantum spin liquid with competing interactions

Magnetic susceptibility, NMR, muon spin relaxation, and inelastic neutron scattering measurements show that kapellasite, Cu_{3}Zn(OH)_{6}Cl_{2}, a geometrically frustrated spin-1/2 kagome antiferromagnet polymorphic with herbertsmithite, is a gapless spin liquid showing unusual dynamic short-range correlations of noncoplanar cuboc2 type which persist down to 20?mK. The Hamiltonian is determined from a fit of a high-temperature series expansion to bulk susceptibility data and possesses competing exchange interactions. The magnetic specific heat calculated from these exchange couplings is in good agreement with experiment. The temperature dependence of the magnetic structure factor and the muon relaxation rate are calculated in a Schwinger-boson approach and compared to experimental results.     

Thermal,structural and rheological properties of starch from avocado seeds (Persea americana,Miller) modified with standard sodium hypochlorite solutions

The avocado (Persea americana, Miller) is a tree that is native to Central/North America (Mexico) and it is very popular worldwide due to its food applications. Its seeds contain an important amount of starch and there is lack of study and understanding regarding the physico-chemical properties of this biopolymer. In this research, starch granules were extracted from avocado seeds and oxidised with standard sodium hypochlorite solutions at 0.5, 1.0 and 2.0 %. Untreated and modified samples were investigated using the following techniques: simultaneous thermogravimetry–differential thermal analysis, differential scanning calorimetry, non-contact atomic force microscopy, rapid viscoamylographic analysis and X-ray powder patterns diffractometry. The main purpose was to investigate the thermal, structural and rheological behaviour of native and oxidised avocado starch, and it was verified that the treated samples showed a decrease in gelatinisation enthalpy and average roughness as well as in the degree of relative crystallinity and pasting properties.     

Phosphor und Phosphate

Analytical and Bioanalytical Chemistry -     

Prion protein self-peptides modulate prion interactions and conversion

Background  

Molecular mechanisms underlying prion agent replication, converting host-encoded cellular prion protein (PrP^C) into the scrapie associated isoform (PrP^Sc), are poorly understood. Selective self-interaction between PrP molecules forms a basis underlying the observed differences of the PrP^C into PrP^Sc conversion process (agent replication). The importance of previously peptide-scanning mapped ovine PrP self-interaction domains on this conversion was investigated by studying the ability of six of these ovine PrP based peptides to modulate two processes; PrP self-interaction and conversion.     

Kinetics of node splitting in evolving complex networks

We introduce a collection of complex networks generated by a combination of preferential attachment and a previously unexamined process of “splitting” nodes of degree k$k$ into k$k$ nodes of degree 1$1$. Four networks are considered, each evolves at each time step by either preferential attachment, with probability p$p$, or splitting with probability 1−p$1-p$. Two methods of attachment are considered; first, attachment of an edge between a newly created node and an existing node in the network, and secondly by attachment of an edge between two existing nodes. Splitting is also considered in two separate ways; first by selecting each node with equal probability and secondly, selecting the node with probability proportional to its degree. Exact solutions for the degree distributions are found and scale-free structure is exhibited in those networks where the candidates for splitting are chosen with uniform probability, those that are chosen preferentially are distributed with a power law with exponential cut-off.     

Thermal, structural and rheological behaviour of native and modified waxy corn starch with hydrochloric acid at different temperatures

In this study, samples of native waxy corn starch, waxy corn starch treated with HCl 0.15 mol L^?1 at 20 and 50 °C, respectively, were analysed. The thermogravimetric curves showed similar behaviour with three main mass losses and a decrease in the thermal stability. The acid hydrolysis in low HCl concentration performed for 4 h caused a decrease in peak temperature (DSC), viscosity peak (RVA), gelatinisation enthalpy (DSC) and relative crystallinity (XRD), and an increase in the average roughness (NC-AFM). The X-ray diffraction patterns displayed the ‘A’ type for all the starch granules.