Polycyclic aromatic and aliphatic hydrocarbons in Mytella charruana, a bivalve mollusk from Mundaú Lagoon, Brazil

The levels of selected organic markers, such as 17 polycyclic aromatic hydrocarbons (PAHs), 16 of which are classified as priority pollutants by the US-EPA, perylene, aliphatic hydrocarbons (linear alkanes) and petroleum biomarkers (hopanes and steranes) were assessed in Mytella charruana, a common bivalve mollusk from the convergence of the Mundaú Lagoon, Maceió, Alagoas, Brazil. The organic markers were evaluated in three campaigns (Jul/2006, Oct/2007 and Feb/2008) aiming to identify pollution sources, understand their status of contamination and determine baseline data looking for future management strategies. Higher Σ16HPAs concentration was observed in organisms with 10-30 mm (80% of the total mass of organisms from Mundaú Lagoon) collected in Feb/2008, whereas in individuals with 30-40 mm, the PAH concentrations were higher during Jul/2006 and Oct/2007. The sugarcane burning in Maceió-AL occurs between October and March. The Flt/(Flt + Py) and BaA/(BaA + Chry) ratios in Feb/2008 indicated a combustion process source. The PAH concentrations in Mytella charruana are below of the limit value considered by the WHO (10 ng g⁻¹ for BaP). However, the results suggest that the sugarcane burning process lead to higher PAH concentrations in these organisms in Feb/2008. Many samples showed significant contamination by petroleum biomarkers, hopanes and steranes. Also, the aliphatic hydrocarbon chromatographic profiles were characteristic of petrogenic sources. The hydrocarbons measured in Mytella charruana from Mundaú Lagoon seems to be impacted by PAH in sugarcane burning periods. On the other hand, urban residues and fishing boats could be pointed as important petrogenic sources of aliphatic hydrocarbons in the same bivalve mollusk.     

Enumeration of maps regardless of genus: Geometric approach

We use the conceptual idea of “maps on orbifolds” and the theory of the non-Euclidean crystallographic groups (NEC groups) to enumerate rooted and unrooted maps (both sensed and unsensed) on surfaces regardless of genus. As a consequence we deduce a formula for the number of chiral pairs of maps. The enumeration principle used in this paper is due to Mednykh (2006) [15], it counts the number of conjugacy classes of subgroups in NEC groups which are in one-to-one correspondence with unrooted (sensed or unsensed) maps.     

Influence of particle size on the SARS-CoV-2 spike protein detection using IgG-capped gold nanoparticles and dynamic light scattering

Due to the unprecedented and ongoing nature of the coronavirus outbreak, the development of rapid immunoassays to detect severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and its highly contagious variants is an important and challenging task. Here, we report the development of polyclonal antibody-functionalized spherical gold nanoparticle biosensors as well as the influence of the nanoparticle sizes on the immunoassay response to detect the SARS-CoV-2 spike protein by dynamic light scattering. By monitoring the increment in the hydrodynamic diameter (ΔD_H) by dynamic light scattering measurements in the antigen–antibody interaction, SARS-CoV-2 S-protein can be detected in only 5 min. The larger the nanoparticles, the larger ΔD_H in the presence of spike protein. From adsorption isotherm, the calculated binding constant (K_D) was 83 nM and the estimated limit of detection was 13 ng/mL (30 pM). The biosensor was stable up to 90 days at 4 °C. Therefore, the biosensor developed in this work could be potentially applied as a fast and sensible immunoassay to detect SARS-CoV-2 infection in patient samples.     

Diffusion of linear paraffins in silicalite studied by the ZLC method in the presence of CO2

The diffusion behavior of C₄–C₁₀ n-alkanes in silicalite-1 has been investigated by using the Zero Length Column method. The diffusivities derived from measurements at different purge rates with different purge gases confirming intracrystalline diffusion control. Data are compared with results reported in the literature for MFI zeolites. The diffusivities were found to be consistent and agree well with data previous obtained by ZLC. However, these data showed a remarkable disagreement with other reported techniques (PFG-NMR, QENS and Permeation). The eventual influence of carbon dioxide (CO₂) adsorption on diffusion properties of n-alkanes in silicalite was also investigated. For this purpose, a series of experiments was performed involving hydrocarbons mixed with CO₂. Data were obtained at 303 K and flow rates between 20 and 80 mL/min. The presence of CO₂ does not seem to influence the intracrystalline transport rate of the investigated light hydrocarbons (n-C₄ and n-C₆). On the other hand, the situation for n-C₈ and n-C₁₀ is more complex. The diffusivity values are higher compared to the previously reported values.     

Complete <Superscript>1</Superscript>H and <Superscript>13</Superscript>C NMR signal assignments and chemical shift calculations of four 1,2,4-oxadiazole-based light-emitting liquid crystals

In this article, we describe the complete ¹H and ¹³C NMR signal assignments of four 1,2,4-oxadiazoles possessing light-emitting liquid crystal properties. These results were obtained by using one- and two-dimensional NMR techniques as well as GIAO (PCM) calculations at B3LYP/6-311++G(d,p) level for compounds 1 and 2a–d. The computed values are in good agreement with the ones obtained experimentally. In addition, some previously unexplained thermotropic features of compounds 2a–d could be clarified with the help of the geometry optimization calculations carried out by us.     

Synthesis of a new solid-phase extractor and its application to preconcentration and determination of lead in water samples

A procedure for preconcentration and determination of lead in water is described. The method is based on the sorption of Pb(II) in a minicolumn packed with a functionalized sorbent and subsequent elution with acidic solution. The determination of lead content in the eluate was carried out using flame atomic absorption spectrometry. The sorbent was prepared by immobilization of the ligand 4-(5'-bromo-2'-thiazolylazo)orcinol on polystyrene-divinylbenzene through an azo spacer. Diazotization and coupling reactions were used for synthesis of the sorbent. Some variables affecting the preconcentration were optimized using a full factorial design. Under optimized conditions, the method presented a detection limit of 0.5 microg/L and enrichment factor of 36 for a sample volume of 25 mL. The accuracy of the method was tested by the determination of lead in a standard reference material (National Institute of Standards and Technology 1643d Fresh Water). The proposed procedure was applied to the determination of lead in samples of natural and drinking waters.     

A generalization of the Lipschitz summation formula and some applications

The Lipschitz formula is extended to a two-variable form. While the theorem itself is of independent interest, we justify its existence further by indicating several applications in the theory of modular forms.

     

Novel antibiotics: macrocyclic peptides designed to trap Holliday junctions

[reaction: see text] Described are the syntheses of eight macrocyclic peptides designed to trap Holliday junctions in bacteria, thereby inhibiting bacterial growth. These macrocycles were designed from linear dimerized hexapeptides that bind to the C-2 symmetrical Holliday junction. They were synthesized from three monomers using a combinatorial-like strategy that permits elucidation of the monomer role in accumulation of Holliday junctions and antibiotic activity. These macrocycles are an important step in designing and synthesizing a new class of antibiotics.     

Monitoring of priority pesticides and other organic pollutants in river water from portugal by gas chromatography-mass spectrometry and liquid chromatography-atmospheric pressure chemical ionization mass spectrometry

Gas chromatography-mass spectrometry (GC-MS) and liquid chromatography-atmospheric pressure chemical ionization mass spectrometry (LC-APCI-MS) were optimized and applied for the trace-level determination of 42 priority pesticides and 33 priority organic pollutants from European Union Directive EC 76/464. First, off-line solid-phase extraction of 200 ml of river water using an OASIS solid-phase extraction cartridge, followed by GC-MS was used. Next, selected samples that were positive to GC-MS were analyzed by LC-APCI-MS in order to detect further polar byproducts or to improve the determination of previously detected polar analytes. The transformation products of triazine pesticides like deethylatrazine (DEA) and deisopropylatrazine (DIA) and compounds such as diuron and several chlorophenols were positively identified by LC-APCI-MS. The present methodology has also been used for searching for new analytes not included in the EC 76/464 list, like Irgarol, DEA and DIA. In addition it was applied to target pollutants in 43 river water samples from Portugal during a pilot survey from April to July 1999. Atrazine followed by simazine and 2,4,6-trichlorophenol were the most ubiquitous compounds detected in this area. The levels detected of the different compounds were in the range of: 0.01-2.73 microg/l, 0.05-0.74 microg/l, 0.02-1.65 microg/l, 0.02-5.43 microg/l, 0.01-0.40 microg/l, 0.01-0.26 microg/l, 0.02-0.61 microg/l, 0.01-3.90 microg/l, 0.01-1.24 microg/l, 0.02-2.3 microg/l, 0.01-0.13 microg/l and 0.01-0.5 microg/l for atrazine, simazine, terbuthylazine, alachlor, metolachlor, Irgarol, propanil; tributhylphosphate, diuron, 2,4,6-trichlorophenol, deisopropylatrazine and deethylatrazine, respectively.