Extractant Assisted Synthesis of Polymer Stabilized Platinum and Palladium Metal Nanoparticles for Sensor Applications

Abstract

Extractant‐assisted synthesis of platinum and palladium polymer‐stabilized metal nanoparticles (PSMNP) was carried out for the first time. The synthesis included the following sequential steps: a) loading of extractant (tributyl‐phosphine oxide, TBPO) with the desired metal ion; b) preparation of a membrane “cocktail” by mixing a metal‐containing extractant, solution of the polymer (PVC or polysulfone) and plastisizer; c) membrane deposition and metal reduction inside the membrane (intermatrix synthesis of PSMNP) by using either a chemical or an electrochemical reduction technique. The electro conductivity of the resulting polymer‐metal nanocomposite membrane appeared by several orders of magnitude higher than that of the metal‐free polymer. The mass‐exchange properties of PSMNP‐containing membranes were shown to depend on both the type of the polymer and the membrane deposition technique.     

Effect of Temperature on C3S and C3S + Nanosilica Hydration and C–S–H Structure

This study aimed to monitor the effect of temperature and the addition of nanosilica on the nanostructure of the C–S–H gel forming during tricalcium silicate (C₃S) hydration. Two types of paste were prepared from a synthesized T₁ C₃S. The first consisted of a blend of deionized water and C₃S at a water/solid ratio of 0.425. In the second, a 90 wt% C₃S + 10 wt% of nanosilica blend was mixed with water at a water/solid ratio of 0.7. The pastes were stored in closed containers at 100% RH and 25°C, 40°C, or 65°C. The hydration reaction was detained after 1, 14, 28, or 62 d with acetone, and then pastes were studied by ²⁹Si magic angle spinning nuclear magnetic resonance (²⁹Si MAS NMR).The main conclusion was that adding nSA expedites C₃S hydration at any age or temperature and modifies the structure of the C–S–H gel formed, two types of C–S–H gel appear. At 25°C and 40°C, more orderly, longer chain gels are initially (1 d) obtained as a result of the pozzolanic reaction between nSA and portlandite (CH) (C–S–H_II gel formation). Subsequently, ongoing C₃S hydration and the concomitant flow of dimers shorten the mean chain length in the gel.     

Integrated combined cycle from natural gas with CO2 capture using a Ca–Cu chemical loop

The integration in a natural gas combined cycle (NGCC) of a novel process for H₂ production using a chemical Ca–Cu loop was proposed. This process is based on the sorption‐enhanced reforming process for H₂ production from natural gas with a CaO/CaCO₃ chemical loop, but including a second Cu/CuO loop to regenerate the Ca‐sorbent. An integration of this system into a NGCC was proposed and a full process simulation exercise of different cases was carried out. Optimizing the operating conditions in the Ca–Cu looping process, 8.1% points of efficiency penalty with respect to a state‐of‐the‐art NGCC are obtained with a CO₂ capture efficiency of 90%. It was demonstrated that the new process can yield power generation efficiencies as high as any other emerging and commercial concepts for power generation from NGCC with CO₂ capture, but maintaining competing advantages of process simplification and compact pressurized reactor design inherent to the Ca–Cu looping system. © 2013 American Institute of Chemical Engineers AIChE J, 59: 2780–2794, 2013     

Contribution of the Tyr-1 in Plantaricin149a to Disrupt Phospholipid Model Membranes

Plantaricin149a (Pln149a) is a cationic antimicrobial peptide, which was suggested to cause membrane destabilization via the carpet mechanism. The mode of action proposed to this antimicrobial peptide describes the induction of an amphipathic α-helix from Ala7 to Lys20, while the N-terminus residues remain in a coil conformation after binding. To better investigate this assumption, the purpose of this study was to determine the contributions of the Tyr1 in Pln149a in the binding to model membranes to promote its destabilization. The Tyr to Ser substitution increased the dissociation constant (K_D) of the antimicrobial peptide from the liposomes (approximately three-fold higher), and decreased the enthalpy of binding to anionic vesicles from −17.2 kcal/mol to −10.2 kcal/mol. The peptide adsorption/incorporation into the negatively charged lipid vesicles was less effective with the Tyr1 substitution and peptide Pln149a perturbed the liposome integrity more than the analog, Pln149S. Taken together, the peptide-lipid interactions that govern the Pln149a antimicrobial activity are found not only in the amphipathic helix, but also in the N-terminus residues, which take part in enthalpic contributions due to the allocation at a lipid-aqueous interface.     

Small Molecules Present in the Cerebrospinal Fluid Metabolome Influence Superoxide Dismutase 1 Aggregation

Superoxide dismutase 1 (SOD1) aggregation is one of the pathological markers of amyotrophic lateral sclerosis (ALS), a fatal neurodegenerative disorder. The underlying molecular grounds of SOD1 pathologic aggregation remains obscure as mutations alone are not exclusively the cause for the formation of protein inclusions. Thus, other components in the cell environment likely play a key role in triggering SOD1 toxic aggregation in ALS. Recently, it was found that ALS patients present a specific altered metabolomic profile in the cerebrospinal fluid (CSF) where SOD1 is also present and potentially interacts with metabolites. Here we have investigated how some of these small molecules affect apoSOD1 structure and aggregation propensity. Our results show that as co-solvents, the tested small molecules do not affect apoSOD1 thermal stability but do influence its tertiary interactions and dynamics, as evidenced by combined biophysical analysis and proteolytic susceptibility. Moreover, these compounds influence apoSOD1 aggregation, decreasing nucleation time and promoting the formation of larger and less soluble aggregates, and in some cases polymeric assemblies apparently composed by spherical species resembling the soluble native protein. We conclude that some components of the ALS metabolome that shape the chemical environment in the CSF may influence apoSOD1 conformers and aggregation.     

Furans and other volatile compounds in ground roasted and espresso coffee using headspace solid-phase microextraction: Effect of roasting speed

The profile of major classes of furanic compounds, as well as other volatile compounds, was evaluated by headspace solid-phase microextraction GC/MS in Arabica ground coffee roasted at three speeds, and in their respective espresso coffees. A total of 113 and 105 volatile compounds were respectively identified in ground coffee and espresso coffee. They were clustered in the following chemical classes: furans, pyrroles, pyridines, pyrazines, ketones, hydrocarbons, aldehydes and others. Results from Principal Component Analysis (PCA) using the data of major volatile class as variables showed that the levels (expressed as relative percentage of total peak area) of furans and pyrroles were higher in espresso samples, whereas those of pyrazines and ketones were higher in ground samples. Slow roasting speed favoured pyridines formation, while medium and fast roasting speed favoured ketones formation. The most representative furanic compound in ground samples was furfuryl alcohol, followed by furfuryl acetate, 2-furfural, 2-methylfuran and 5-methylfurfural. In espresso samples, the levels of 2-methylfuran, 2-furfural, furfuryl formate, 5-methylfurfural and furfuryl acetate were largely increased while the proportion of furfuryl alcohol was strongly reduced in comparison to ground coffee. High roast speed increased formation of 2-furfural and 5-methyl furfural in espresso coffee.     

Total content and dialyzable iron and zinc in foods from northern and Southern Mexico

Developing countries diets are based on a variety of plant foods that often are the main suppliers of important amounts of iron (Fe) and zinc (Zn). The objectives of this study were 1) to measure the total and dialyzable amounts of Fe and Zn in foods from Northern Mexico (Sonora) and from Southern Mexico (Oaxaca) and 2) to evaluate the effect of meat content of diets on the dialyzable amount of Fe and Zn. Methods to calculate the total dialyzable amount of Fe and Zn, were those of the AOAC and of Shen et al. Total Fe in e northern Mexican foods went from 0.78 +/- 0.0 to 11.59 +/- to 0.03 mg/ 100g (dry weight, DW); in southern Mexican foods the same micronutrient amounts were 0.86 +/- 0.18 to 8.8 +/- 0.57 mg/100 g (BS). Total Zn values were 0.91 +/- 0.00 to 13.58 +/- 0.05 mg/100 g (DW) in Sonora, and 0.64 +/- 0.18 to 20.80 +/- 0.33 mg/100 g (DW) in Oaxaca. In northern Mexico, foods dialyzable Fe had values from 0.1 +/- 0.04% to 10.6 +/- 0.36% and for Zn from 4.0 +/- 0.21% to 55.32 +/- 0.14%. Meanwhile, the range of values of dialyzable Fe for foods from Oaxaca were from 0.22 +/- 0.06% to 9.40 +/- 0.14% for and from 2.41 +/- 0.26% to 54.27 +/- 1.49% for dialyzable Zn. The average value for dialyzable Fe was higher in the foods that contained meat or meat products (p= 0.001).     

Effect of binder system on the thermophysical properties of 3D-printed zirconia ceramics

Fabrication of 3D-printed ceramic parts with high complexity and high spatial resolution often demands low wall thickness as well as high stiffness at the green state, whereas printing simpler geometries may tolerate thicker, more compliant walls with the advantage of a rapid binder-burn-out and sintering process. In this work, the influence of the binder system on the thermophysical properties of 3D-printed stabilized zirconia ceramics was investigated. Samples were fabricated with the lithography-based ceramic manufacturing (LCM) technology using two different photosensitive ceramic suspensions (LithaCon 3Y230 and LithaCon 3Y210), with the same ZrO₂ powder. A significant difference in stiffness in the green state (~3 MPa vs. ~32 MPa for LithaCon 3Y230 and LithaCon 3Y210, respectively) was measured, associated with a rather loose or a linked network formed in the binder due to photopolymerization. Both materials reached high relative densities, that is, >99%, exhibiting a homogeneous fine-grained microstructure. No significant differences on the coefficient of thermal expansion (11.18 ppm/K vs. 11.17 ppm/K) or Young's modulus (207 GPa vs. 205 GPa) were measured, thus demonstrating the potential of tailoring binder systems to achieve the required accuracy in 3D-printed parts, without detrimental effects on material's microstructure and thermophysical properties at the sintered state.     

Characterization of Crude and Partially Purified Lipase from Geotrichum candidum Obtained with Different Nitrogen Sources

Lipases from Geotrichum candidum were produced in two different medium: A = 12 % (w/v) clarified corn steep liquor (CCSL) + 0.6 % (w/v) soybean oil (SO) and B = 3.5 % (w/v) yeast hydrolysate (YH) + 0.7 % (w/v) SO. Lipases were partially purified from both media by hydrophobic interaction chromatography using 3.0 mol L^?1 of NaCl as mobile phase, and they were characterized in the crude and partially purified forms. The recovery of lipase activity from CCSL and YH via HIC were 96 and 94.3 %, and the purification factors were 44.3 and 86.7‐fold, respectively. All evaluated lipases had similar optimum pH (7.0–7.7), but, for the CCSL crude lipase, optimum temperature (47 °C) was 10 °C higher than others lipases evaluated. CCSL crude lipase possessed a higher thermo stability than YH crude lipase, e.g., at 37 °C (pH 7.0) the half‐life of CCSL crude lipase was 19.25 h and at pH 8.0 (30 °C) the half‐life was 48 h, which are five and ten times higher than with YH crude lipase, respectively. On the other hand, the YH crude lipase possessed a higher catalytic constant (k_cat = 2.3 min^?1) but with almost the same catalytic efficiency (K_m/k_cat = 32.12 mg mL min^?1) in relation to CCSL crude lipase. The lipases differ in biocatalytic properties between substrates, suggesting that the two lipases can be employed for different applications.     

Pain Modulation from the Locus Coeruleus in a Model of Hydrocephalus: Searching for Oxidative Stress-Induced Noradrenergic Neuroprotection

Pain transmission at the spinal cord is modulated by noradrenaline (NA)-mediated actions that arise from supraspinal areas. We studied the locus coeruleus (LC) to evaluate the expression of the cathecolamine-synthetizing enzyme tyrosine hydroxylase (TH) and search for local oxidative stress and possible consequences in descending pain modulation in a model of hydrocephalus, a disease characterized by enlargement of the cerebral ventricular system usually due to the obstruction of cerebrospinal fluid flow. Four weeks after kaolin injection into the cisterna magna, immunodetection of the catecholamine-synthetizing enzymes TH and dopamine-β-hydroxylase (DBH) was performed in the LC and spinal cord. Colocalization of the oxidative stress marker 8-OHdG (8-hydroxyguanosine; 8-OHdG), with TH in the LC was performed. Formalin was injected in the hindpaw both for behavioral nociceptive evaluation and the immunodetection of Fos expression in the spinal cord. Hydrocephalic rats presented with a higher expression of TH at the LC, of TH and DBH at the spinal dorsal horn along with decreased nociceptive behavioral responses in the second (inflammatory) phase of the formalin test, and formalin-evoked Fos expression at the spinal dorsal horn. The expression of 8-OHdG was increased in the LC neurons, with higher co-localization in TH-immunoreactive neurons. Collectively, the results indicate increased noradrenergic expression at the LC during hydrocephalus. The strong oxidative stress damage at the LC neurons may lead to local neuroprotective-mediated increases in NA levels. The increased expression of catecholamine-synthetizing enzymes along with the decreased nociception-induced neuronal activation of dorsal horn neurons and behavioral pain signs may indicate that hydrocephalus is associated with alterations in descending pain modulation.