Molybdenum and tungsten enzymes require specific chaperones for folding and cofactor insertion. PaoD is the chaperone of the periplasmic aldehyde oxidoreductase PaoABC. It is the last gene in the paoABCD operon in Escherichia coli and its presence is crucial for obtaining mature enzyme. PaoD is an unstable, 35 kDa, protein. Our biochemical studies showed that it is a dimer in solution with a tendency to form large aggregates, especially after freezing/thawing cycles. In order to improve stability, PaoD was thawed in the presence of two ionic liquids [C4mim]Cl and [C2OHmim]PF6 and no protein precipitation was observed. This allowed protein concentration and crystallization using polyethylene glycol or ammonium sulfate as precipitating agents. Saturation transfer difference – nuclear magnetic resonance (STD-NMR) experiments have also been performed in order to investigate the effect of the ionic liquids in the stabilization process, showing a clear interaction between the acidic ring protons of the cation and, most likely, negatively charged residues at the protein surface. DLS assays also show a reduction of the overall size of the protein aggregates in presence of ionic liquids. Furthermore, cofactor binding studies on PaoD showed that the protein is able to discriminate between molybdenum and tungsten bound to the molybdenum cofactor, since only a Mo-MPT form of the cofactor remained bound to PaoD.

Aminophenyl boronic acids can form reversible covalent ester interactions with cis-diol-containing molecules, serving as a selective tool for binding glycoproteins as antibody molecules that possess oligosaccharides in both the Fv and Fc regions. In this study, amino phenyl boronic acid (APBA) magnetic particles (MPs) were applied for the magnetic separation of antibody molecules. Iron oxide MPs were firstly coated with dextran to avoid non-specific binding and then with 3-glycidyloxypropyl trimethoxysilane to allow further covalent coupling of APBA (APBA_MP). When contacted with pure protein solutions of human IgG (hIgG) and bovine serum albumin (BSA), APBA_MP bound 170 ± 10 mg hIgG g−1 MP and eluted 160 ± 5 mg hIgG g−1 MP, while binding only 15 ± 5 mg BSA g−1 MP. The affinity constant for the interaction between hIgG and APBA_MP was estimated as 4.9 × 105 M−1 (Ka) with a theoretical maximum capacity of 492 mg hIgG adsorbed g−1 MP (Qmax), whereas control particles bound a negligible amount of hIgG and presented an estimated theoretical maximum capacity of 3.1 mg hIgG adsorbed g−1 MP (Qmax). APBA_MPs were also tested for antibody purification directly from CHO cell supernatants. The particles were able to bind 98% of IgG loaded and to recover 95% of pure IgG (purity greater than 98%) at extremely mild conditions.

Plasmonic light trapping in thin film silicon solar cells is a promising route to achieve high efficiency with reduced volumes of semiconductor material. In this paper, we study the enhancement in the opto-electronic performance of thin a-Si:H solar cells due to the light scattering effects of plasmonic back reflectors (PBRs), composed of self-assembled silver nanoparticles (NPs), incorporated on the cells’ rear contact. The optical properties of the PBRs are investigated according to the morphology of the NPs, which can be tuned by the fabrication parameters. By analyzing sets of solar cells built on distinct PBRs we show that the photocurrent enhancement achieved in the a-Si:H light trapping window (600 – 800 nm) stays in linear relation with the PBRs diffuse reflection. The best-performing PBRs allow a pronounced broadband photocurrent enhancement in the cells which is attributed not only to the plasmon-assisted light scattering from the NPs but also to the front surface texture originated from the conformal growth of the cell material over the particles. As a result, remarkably high values of Jsc and Voc are achieved in comparison to those previously reported in the literature for the same type of devices.

The purification of recombinant proteins by affinity chromatography is one of the most efficient strategies due to the high recovery yields and purity achieved. However, this is dependent on the availability of specific affinity adsorbents for each particular target protein. The diversity of proteins to be purified augments the complexity and number of specific affinity adsorbents needed, and therefore generic platforms for the purification of recombinant proteins are appealing strategies. This justifies why genetically encoded affinity tags became so popular for recombinant protein purification, as these systems only require specific ligands for the capture of the fusion protein through a pre-defined affinity tag tail. There is a wide range of available affinity pairs “tag-ligand” combining biological or structural affinity ligands with the respective binding tags. This review gives a general overview of the well-established “tag-ligand” systems available for fusion protein purification and also explores current unconventional strategies under development.

The color sensing ability of a data acquisition prototype system integrating a 32 linear array of 1D amorphous silicon position sensitive detectors (PSD) was analyzed. Besides being used to reproduce a 3D profile of highly reflective surfaces, here we show that it can also differentiate primary red, green, blue (RGB) and derived colors. This was realized by using an incident beam with a RGB color combination and adequate integration times taking into account that a color surface mostly reflects its corresponding color. A mean colorimetric error of 25.7 was obtained. Overall, we show that color detection is possible via the use of this sensor array system, composed by a simpler amorphous silicon pin junction.

The human macrophage galactose-type lectin (MGL) is a key physiological receptor for the carcinoma-associated Tn antigen (GalNAc-α-1-O-Ser/Thr) in mucins. NMR and modeling-based data on the molecular recognition features of synthetic Tn-bearing glycopeptides by MGL are presented. Cognate epitopes on the sugar and matching key amino acids involved in the interaction were identified by saturation transfer difference (STD) NMR spectroscopy. Only the amino acids close to the glycosylation site in the peptides are involved in lectin contact. Moreover, control experiments with non-glycosylated MUC1 peptides unequivocally showed that the sugar residue is essential for MGL binding, as is Ca(2+) . NMR data were complemented with molecular dynamics simulations and Corcema-ST to establish a 3D view on the molecular recognition process between Gal, GalNAc, and the Tn-presenting glycopeptides and MGL. Gal and GalNAc have a dual binding mode with opposite trend of the main interaction pattern and the differences in affinity can be explained by additional hydrogen bonds and CH-π contacts involving exclusively the NHAc moiety.

Tn antigen (α-O-GalNAc-Ser/Thr) is a convenient cancer biomarker that is recognized by antibodies and lectins. This work yields remarkable results for two plant lectins in terms of epitope recognition and reveals that these receptors show higher affinity for Tn antigen when it is incorporated in the Pro-Asp-Thr-Arg (PDTR) peptide region of mucin MUC1. In contrast, a significant affinity loss is observed when Tn antigen is located in the Ala-His-Gly-Val-Thr-Ser-Ala (AHGVTSA) or Ala-Pro-Gly-Ser-Thr-Ala-Pro (APGSTAP) fragments. Our data indicate that the charged residues, Arg and Asp, present in the PDTR sequence establish noteworthy fundamental interactions with the lectin surface as well as fix the conformation of the peptide backbone, favoring the presentation of the sugar moiety toward the lectin. These results may help to better understand glycopeptide-lectin interactions and may contribute to engineer new binding sites, allowing novel glycosensors for Tn antigen detection to be designed

PpcA is the most abundant member of a family of five triheme cytochromes c7 in the bacterium Geobacter sulfurreducens (Gs) and is the most likely carrier of electrons destined for outer surface during respiration on solid metal oxides, a process that requires extracellular electron transfer. This cytochrome has the highest content of lysine residues (24%) among the family, and it was suggested to be involved in e-/H(+) energy transduction processes. In the present work, we investigated the functional role of lysine residues strategically located in the vicinity of each heme group. Each lysine was replaced by glutamine or glutamic acid to evaluate the effects of a neutral or negatively charged residue in each position. The results showed that replacing Lys9 (located near heme IV), Lys18 (near heme I) or Lys22 (between hemes I and III) has essentially no effect on the redox properties of the heme groups and are probably involved in redox partner recognition. On the other hand, Lys43 (near heme IV), Lys52 (between hemes III and IV) and Lys60 (near heme III) are crucial in the regulation of the functional mechanism of PpcA, namely in the selection of microstates that allow the protein to establish preferential e-/H(+) transfer pathways. The results showed that the preferred e-/H(+) transfer pathways are only established when heme III is the last heme to oxidize, a feature reinforced by a higher difference between its reduction potential and that of its predecessor in the order of oxidation. We also showed that K43 and K52 mutants keep the mechanistic features of PpcA by establishing preferential e-/H+ transfer pathways at lower reduction potential values than the wild-type protein, a property that can enable rational design of Gs strains with optimized extracellular electron transfer capabilities.

The increase of renewables in power sector, together with the increase of their electricity share in final energy consumption, is changing our perception about energy security with diverse and contradictory statements. The Portuguese security of electricity supply is analyzed in this study by comparing selected indicators for 2. years before and after the high increase of onshore wind since 2005. Our goal is to find how the security of electricity supply was impacted by the penetration of renewables, taking a supply chain approach. Our analysis highlights that the penetration of renewables has decreased the energy dependence of the power sector by more than 20% between 2004 and 2011, while risks related to the concentration of natural gas suppliers and to the still-high share of fossil fuels suffering from price volatility are discussed. We observed a significant improvement in power interconnections with Spain, as well as an increase of the de-rated generation capacity margin, allowing proper management of renewable power intermittency if necessary, thereby improving power security. Although the share of intermittent renewables almost quadrupled in total installed capacity between those years, the indicators reveal an improvement in the quality of transport and distribution when delivering electricity to end-users. Although electricity prices increased, mainly due to taxes, the lack of energy efficiency is an aspect deserving improvement to alleviate the pressure on electricity security, mainly at high peak demands.

Iron oxide nanoparticles are having been extensively investigated for several biomedical applications such as hyperthermia and magnetic resonance imaging. However, one of the biggest problems of these nanoparticles is their aggregation.
Taking this into account, in this study the influence of three different surfactants (oleic acid, sodium citrate and Triton X-100) each one with various concentrations in the colloidal solutions stability was analyzed by using a rapid and facile method, the variation in the optical absorbance along time.
The synthesized nanoparticles through chemical precipitation showed an average size of 9 nm and a narrow size distribution. X-ray diffraction pattern and Fourier Transform Infrared analysis confirmed the presence of pure magnetite. SQUID measurements showed superparamagnetic properties with a blocking temperature around 155 K. In addition it was observed that neither sodium citrate nor Triton X-100 influences the magnetic properties of the nanoparticles. On the other hand, oleic acid in a concentration of 64 mM decreases the saturation magnetization from 67 to 45 emu/g. Oleic acid exhibits a good performance as stabilizer of the iron oxide nanoparticles in an aqueous solution for 24 h, for concentrations that lead to the formation of the double layer.

Iron oxide nanoparticles are having been extensively investigated for several biomedical applications such as hyperthermia and magnetic resonance imaging. However, one of the biggest problems of these nanoparticles is their aggregation.

Taking this into account, in this study the influence of three different surfactants (oleic acid, sodium citrate and Triton X-100) each one with various concentrations in the colloidal solutions stability was analyzed by using a rapid and facile method, the variation in the optical absorbance along time.

The synthesized nanoparticles through chemical precipitation showed an average size of 9 nm and a narrow size distribution. X-ray diffraction pattern and Fourier Transform Infrared analysis confirmed the presence of pure magnetite. SQUID measurements showed superparamagnetic properties with a blocking temperature around 155 K. In addition it was observed that neither sodium citrate nor Triton X-100 influences the magnetic properties of the nanoparticles. On the other hand, oleic acid in a concentration of 64 mM decreases the saturation magnetization from 67 to 45 emu/g. Oleic acid exhibits a good performance as stabilizer of the iron oxide nanoparticles in an aqueous solution for 24 h, for concentrations that lead to the formation of the double layer.

The electrospinning of polycaprolactone (PCL) dissolved in glacial acetic acid and the characterization of the resultant nonwoven fiber mats is reported in this work. For comparison purposes, PCL fiber mats were also obtained by electrospinning the polymer dissolved in chloroform. Given the processing parameters chosen, results show that 14 and 17 wt % PCL solutions are not viscous enough and yield beaded fibers, 20 and 23 wt % solutions give rise to high quality fibers and 26 wt % solutions yield mostly irregular and fused fibers. The nonwoven mats are highly porous, retain the high tensile strain of PCL, and the fibers are semicrystalline. Cells adhere and proliferate equally well on all mats, irrespective of the solvent used in their production. In conclusion, mats obtained by electrospinning PCL dissolved in acetic acid are also a good option to consider when producing scaffolds for tissue engineering. Moreover, acetic acid is miscible with polar solvents, which may allow easier blending of PCL with hydrophilic polymers and therefore achieve the production of electrospun nanofibers with improved properties.