Source apportionment of organic pollutants of a highway-traffic-influenced urban area in Bayreuth (Germany) using biomarker and stable carbon isotope signatures

Traffic- and urban-influenced areas are prone to enhanced pollution with products of incomplete combustion of fossil fuels and biomass such as black carbon or polycyclic aromatic hydrocarbons (PAHs). Black carbon is composed of aromatic and graphitic structures and may act as a carrier for pollutants such as PAHs and heavy metals. However, little is known about possible contributions of traffic-derived black carbon to the black carbon inventory in soils. Similar uncertainties exist regarding the contribution of different pollutant sources to total PAH and black carbon contents. Therefore, the objective of this study was to quantify the importance of traffic pollution to black carbon and PAH inventories in soils. PAH contamination of soils adjacent to a major German highway in the urban area of Bayreuth with about 50,000 vehicles per day was in the same order of magnitude compared to highway-close soils reported in other studies. Using molecular (black carbon and PAHs) and compound-specific stable carbon isotope evidence (PAHs) it was demonstrated that this contamination originated not only from automobile exhausts, here primarily diesel, but also from tire abrasion and tailpipe soot which significantly contributed to the traffic-caused black carbon and PAH contamination. Low molecular weight PAHs were more widely transported than their heavy molecular counterparts (local distillation), whereas highway-traffic-caused black carbon contamination was distributed to at least 30 m from the highway. On the other hand, urban fire exhausts were distributed more homogeneously among the urban area.     

Investigation of Structural Determinants for the Substrate Specificity in the Zinc‐Dependent Alcohol Dehydrogenase CPCR2 from Candida parapsilosis

Zinc‐dependent alcohol dehydrogenases (ADHs) are a class of enzymes applied in different biocatalytic processes ranging from lab to industrial scale. However, one drawback is the limited substrate range, necessitating a whole array of different ADHs for the relevant substrate classes. In this study, we investigated structural determinants of the substrate spectrum in the zinc‐dependent ADH carbonyl reductase 2 from Candida parapsilosis (CPCR2), combining methods of mutational analysis with in silico substrate docking. Assigned active site residues were genetically randomized, and the resulting mutant libraries were screened with a selection of challenging carbonyl substrates. Three variants (C57A, W116K, and L119M) with improved activities toward different substrates were detected at neighboring positions in the active site. Thus, all possible combinations of the mutations were generated and characterized for their substrate specificity, yielding several improved variants. The most interesting were a C57A variant, with a 27‐fold increase in specific activity for 4′‐acetamidoacetophenone, and the double mutant CPCR2 B16‐(C57A, L119M), with a 45‐fold improvement in the k_cat?K_M^?1 value. The obtained variants were further investigated by in silico docking experiments. The results indicate that the mentioned residues are structural determinants of the substrate specificity of CPCR2, being major players in the definition of the active site. Comparison of these results with closely related enzymes suggests that these might even be transferred to other ADHs.     

Improvement of Modified Wood Properties with Addition of Chestnut Tannins in Lactic Acid-Based Treatments

Wood modification treatments based on lactic acid oligomers (OLA) and monomers (LA) enhance beech dimensional stability (up to 70%) and biological resistance (less than 3% weight loss according to EN113). Chestnut wood tannins natural biological activity might improve the modified wood durability with milder curing conditions. Treatment consisted of the impregnation of monomers or oligomers mixtures followed by curing (140?°C/160?°C for 48h). Tannins addition is almost inconsequential with oligomeric-based treatment but improved the monomeric-based treatment. In this case, modified wood biological resistance and product persistence were increased. OLA impregnated wood cured at 160?°C was always the best performing treatment regarding dimensional stability and durability, but the addition of tannins in LA systems conferred promising properties to wood allowing simplification of the modification process.     

Correlation of Mitochondrial Haplotypes with Cuticular Hydrocarbon Phenotypes of Sympatric Reticulitermes Species from the Southeastern United States

Three sympatric Reticulitermes species have been identified in Georgia, USA, based on morphological characters from alates and soldiers: R. flavipes, R. virginicus, and R. hageni, but species identification at individual collection sites is often difficult because alate production is seasonal and soldiers comprise 1–3% of the colony. We therefore set up an experiment to determine if chemical phenotypes and mtDNA haplotypes can be used together to separate species of subterranean termites. Subterranean termites of the order Reticulitermes (Isoptera: Rhinotermitidae) were collected from 20 inspection ports across four soil provinces in Georgia. Each collection was identified to species using dichotomous keys. Two collections, HH11 and BH25, however, could not be unequivocally keyed to species and were classified as unknown. The mitochondrial cytochrome oxidase II (COII) gene was sequenced from individual members of each collection and the variation in cuticular hydrocarbon phenotypes from these same collections was characterized. The cuticular hydrocarbon and mtDNA phylogenetic analyses show agreement with both unknown collections falling out in a separate clade. Specimens from HH11 nad BH25 are different morphologically, chemically, and genetically from the three known sympatric species in Georgia. Our results suggest that these two collections may represent at least one new taxon in Reticulitermes. Furthermore, the association of cuticular hydrocarbon phenotypes and mtDNA haplotypes demonstrates that, when combined with morphological characters, they are useful in separating known species, determining new species, and understanding termite evolution.     

High yield preparation of all-organic raspberry-like particles by heterocoagulation via hydrogen bonding interaction

We describe here a straightforward strategy towards the high yield preparation of raspberry-like all-organic particles. Poly(acrylic acid)-b-poly(butyl acrylate) core–shell nanoparticles (D ∼ 80 nm) and larger poly(ethylene oxide)-b-poly(butyl acrylate) core–shell (D ∼ 230 nm), synthesized by RAFT emulsion polymerization, were mixed at high solids content (23 wt%) at room temperature without any particular precaution (no dropwise addition, no pH adjustment). Raspberry-like particles constituted of one central PEO-b-PBA particle surrounded by about thirty PAA-b-PBA particles were successfully obtained, with no coagulum formation. The heteroaggregation process is probably driven by the hydrogen-bond interactions between the PAA and the PEO shells of the particles. The raspberry-like particles were characterized using electron microscopy (TEM and cryo-TEM), dynamic light scattering (DLS), chromatography (HDC) and calorimetry (ITC), demonstrating the selectivity of the process.     

Generation of Liposomes to Study the Effect of Mycobacterium Tuberculosis Lipids on HIV-1 cis- and trans-Infections

Tuberculosis (TB) is the leading cause of death among HIV-1-infected individuals and Mycobacterium tuberculosis (Mtb) co-infection is an early precipitate to AIDS. We aimed to determine whether Mtb strains differentially modulate cellular susceptibility to HIV-1 infection (cis- and trans-infection), via surface receptor interaction by their cell envelope lipids. Total lipids from pathogenic (lineage 4 Mtb H37Rv, CDC1551 and lineage 2 Mtb HN878, EU127) and non-pathogenic (Mycobacterium bovis BCG and Mycobacterium smegmatis) Mycobacterium strains were integrated into liposomes mimicking the lipid distribution and antigen accessibility of the mycobacterial cell wall. The resulting liposomes were tested for modulating in vitro HIV-1 cis- and trans-infection of TZM-bl cells using single-cycle infectious virus particles. Mtb glycolipids did not affect HIV-1 direct infection however, trans-infection of both R5 and X4 tropic HIV-1 strains were impaired in the presence of glycolipids from M. bovis, Mtb H37Rv and Mtb EU127 strains when using Raji-DC-SIGN cells or immature and mature dendritic cells (DCs) to capture virus. SL1, PDIM and TDM lipids were identified to be involved in DC-SIGN recognition and impairment of HIV-1 trans-infection. These findings indicate that variant strains of Mtb have differential effect on HIV-1 trans-infection with the potential to influence HIV-1 disease course in co-infected individuals.