Mapping of possible prion protein self-interaction domains using peptide arrays

Background  

The common event in transmissible spongiform encephalopathies (TSEs) or prion diseases is the conversion of host-encoded protease sensitive cellular prion protein (PrP^C) into strain dependent isoforms of scrapie associated protease resistant isoform (PrP^Sc) of prion protein (PrP). These processes are determined by similarities as well as strain dependent variations in the PrP structure. Selective self-interaction between PrP molecules is the most probable basis for initiation of these processes, potentially influenced by chaperone molecules, however the mechanisms behind these processes are far from understood. We previously determined that polymorphisms do not affect initial PrP^C to PrP^Sc binding but rather modulate a subsequent step in the conversion process. Determining possible sites of self-interaction could elucidate which amino acid(s) or amino acid sequences contribute to binding and further conversion into other isoforms. To this end, ovine – and bovine PrP peptide-arrays consisting of 15-mer overlapping peptides were probed with recombinant sheep PrP^C fused to maltose binding protein (MBP-PrP).     

Studies on photoinduced effects in pulse-electrodeposited Ag/Hg-1212/CdSe hetero-nanostructures

Metal/superconductor/semiconductor (Ag/Hg-1212/CdSe) hetero-nanostructures have been fabricated using pulse-electrodeposition technique and are characterized by X-ray diffraction (XRD), full-width at half-maximum (FWHM) and scanning electron microscopy (SEM) studies. The junction capacitance of Ag/Hg-1212, Hg-1212/CdSe and Ag/Hg-1212/CdSe heterojunctions is measured in dark and under laser irradiation at room temperature. The nature of the junction formed and built-in-junction potentials were determined. The increase in carrier concentration across the junction due to photo-irradiation has been observed.     

Effect of laser irradiation of C-V characteristics of electrodeposited Ag/Tl-2223/CdSe hetero-nanostructures

One of the innovative technological directions for the high-temperature superconductors has been persued by fabricating the heteroepitaxial multilayer structures such as superconductor-semiconductor heterostructures. In the present investigation, metal/superconductor/semiconductor (Ag/Tl-2223/CdSe) hetero-nanostructures have successfully been fabricated using dc electrodeposition technique and were characterized by X-ray diffraction (XRD), full-width at half-maximum (FWHM) and scanning electron microscopy (SEM) studies. The measurement of junction capacitance as a function of biasing voltage was used for the estimation of junction built-in-potential (V _D) and to study the charge distribution in a heterojunction. The Mott-Schottky plots were measured for each junction in dark and under the photo-irradiation. The effect of laser irradiation on C-V characteristics of hetero-nanostructure has been studied.     

Glycopeptide and Oligosaccharide Libraries

Despite the burgeoning interest in the various biological functions and consequent therapeutic potential of the vast number of oligosaccharides found in nature on glycoproteins and cell surfaces, the development of combinatorial carbohydrate chemistry has not progressed as rapidly as expected. The reason for this imbalance is rooted in the difficulty of oligosaccharide assembly and analysis that renders synthesis a rather cumbersome endeavor. Parallel approaches that generate series of analogous compounds rather than real libraries have therefore typically been used. Since generally low affinity is obtained for interactions between carbohydrate receptors and modified oligosaccharides designed as mimetics of natural carbohydrate ligands, glycopeptides have been explored as alternative mimics. Glycopeptides have been proven in many cases to be superior ligands with higher affinity for a receptor than the natural carbohydrate ligand. High-affinity glycopeptide ligands have been found for several types of receptors including the E-, P-, and L-selectins, toxins, glycohydrolases, bacterial adhesins, and the mannose-6-phosphate receptor. Furthermore, the assembly of glycopeptides is considerably more facile than that of oligosaccharides and the process can be adapted to combinatorial synthesis with either glycosylated amino acid building blocks or by direct glycosylation of peptide templates. The application of the split and combine approach using ladder synthesis has allowed the generation of very large numbers of compounds which could be analyzed and screened for binding of receptors on solid phase. This powerful technique can be used generally for the identification and analysis of the complex interaction between the carbohydrates and their receptors.     

Stability studies of vitamins in three food reference materials

Summary Stability in storage and shipment of retinol, -tocopherol, vitamins B₁, B₂ and C in three foods was studied to assess the feasibility of certifying the vitamin content of three food RMs, whole milk powder (CRM 380), pork muscle (CRM 384) and freeze-dried haricot beans (CRM 383); these were recently certified for major dietary components and major elements. Interpretation of the long-term stability data was complicated by a dominant analytical variability over the measurement period. The long-term stability study (24 months) gave evidence of deterioration of vitamin B₂ in pork muscle. The other vitamins studied seemed to be acceptably stable at –18°C and +4°C. Additional studies showed stability of retinol in milk powder for 34 months and of vitamin C in haricot beans for 31 months at –18°C and +4°C. Long-term storage seems to be possible at a temperature not higher than +4°C except for vitamin B₂. A short-term stability study at +25°C and +30°C for 6 weeks showed acceptable stability of retinol and -tocopherol in milk powder (CRM 380) and of vitamin C in haricot beans (CRM 383). However, storage at +42°C induces degradation of retinol, -tocopherol and vitamin C.     

Improvements in the determination of vitamins in food through intercomparisons and preparation of RMs for vitamin analysis within the BCR1 programme

Summary In order to improve the methods for the determination of vitamins in food for nutritional purposes, the Commission's Community Bureau of Reference (BCR) has initiated a comprehensive research programme consisting of intercomparisons of methods to identify and eliminate sources of error and the preparation of reference materials (RMs). Six food RMs have been prepared to date including brussels sprouts, mixed vegetables and pigs' liver (all in the lyophilised form), vitamin enriched milk powder, wholemeal flour and margarine. The first five materials have been packaged into heat sealable, aluminium-laminate sachets under an inert atmosphere; margarine is a canned product. The initial homogeneity results have indicated no detectable signs of inhomogeneity for the vitamins/RMs investigated. Stability testing has monitored both short-term stability at elevated temperatures (+25 to 40°C, 8 weeks) and long-term stability –30 to +20°C, 36 months). The former was used to evaluate the effect of adverse shipment conditions on vitamin stability. Vitamins C and B₁, two of the more labile vitamins, have been found to be stable for up to 4 weeks at +25°C and 8 weeks at +37°C in brussels sprouts (RM 431) and wholemeal flour (RM 122), respectively.The results of long-term stability testing of vitamins C and B₁ in these RMs indicate there was no significant degradation of vitamin C in RM 431 for up to 24 months at –18 and +4°C when the data was expressed on the basis of the –30°C data (analytical control). Similarly, no significant degradation for vitamin B₁ in RM 122 was found at +4 and +20°C for up to 12 months, again after expressing the data on the basis of the analytical control (–20°C). Once acceptable homogeneity and stability results have been found, certification studies for each vitamin/RM are planned.     

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.