Binding of SARS-CoV-2 to Cell Receptors: A Tale of Molecular Evolution

The magnified infectious power of the SARS-CoV-2 virus compared to its precursor SARS-CoV is intimately linked to an enhanced ability in the mutated virus to find available hydrogen-bond sites in the host cells. This characteristic is acquired during virus evolution because of the selective pressure exerted at the molecular level. We pinpoint the specific residue (in the virus) to residue (in the cell) contacts during the initial recognition and binding and show that the virus⋅⋅⋅cell interaction is mainly due to an extensive network of hydrogen bonds and to a large surface of noncovalent interactions. In addition to the formal quantum characterization of bonding interactions, computation of absorption spectra for the specific virus⋅⋅⋅cell interacting residues yields significant shifts of Δλ_max=47 and 66 nm in the wavelength for maximum absorption in the complex with respect to the isolated host and virus, respectively.     

Assessing concerns of interested parties when predicting the significance of environmental impacts related to the construction process of residential buildings

The most common challenges and obstacles encountered by construction organizations during the process of implementing and using environmental management systems are related to the inherent peculiarities of the construction sector. Several studies have shown that one of the issues involving the greatest level of uncertainty is the identification and assessment of environmental impacts. In order to improve the identification of the significance of environmental impacts of construction projects and sites, which will lead to greater efficiency and robustness in environmental management systems, this paper extends the systematic approach for identifying and assessing potential adverse environmental impacts at the pre-construction stage presented in Gangolells et al. (2009) by introducing the assessment of the concerns of interested parties. By considering concerns amongst internal and external interested parties, one can assess the significance of environmental impacts taking into account not only the severity of the impacts but also local perceptions and international challenges, thereby ensuring that the determination of the impacts’ significance is appropriate to the particular socioeconomic and biophysical environments surrounding construction sites. In order to quantitatively measure concerns among internal and external interested parties for each of the 37 environmental impacts related to a construction project, we developed corresponding indicators and assessment scales with the help of a panel of experts. A series of χ² tests conducted over 76 new-start construction projects clearly revealed that the severity of environmental impacts is not correlated with the concerns of interested parties. The development of a formal quantitative method and the subsequent definition of a threshold make it possible to obtain advance knowledge of the significance – and, therefore, the acceptability – of each potential environmental impact for a particular construction project. A total score for each construction project alternative is also obtained, so the improved methodology provides a consistent basis for comparing construction companies and construction sites. Finally, two case studies are presented in order to demonstrate the benefits of the improved methodology.     

Influence of an upstream building on the wind-induced mean suction on the flat roof of a low-rise building

The effect of an upstream building on the suction forces on the flat roof of a low-rise building placed in the wake of the former is analyzed. The analysis has been performed by wind tunnel testing of a flat roof, low-rise building model equipped with pressure taps on the roof and different block-type buildings (only configurations where the upstream building is as high or higher than the downstream one are considered in this paper). The influence of the distance between both buildings on the wind loads on the downstream building roof is analyzed, as well as the height of the upstream one and the wind angle of incidence. Experimental results reveal that the wind load increases as the relative height of the upstream building increases, the wind load being highest for intermediate distances between buildings, when a passage between them is formed.     

Kinetic stability of nitrogen cubane inside the fullerene cage: Molecular dynamics study

Abstract

Using tight-binding molecular dynamics simulations, we study kinetic stability of the nitrogen cubane inside the fullerene carbon cage. The main identified mechanism of N₈ decomposition is the N–N bond breaking with the further rapid “splitting” into the N₂ molecules that can form the strong covalent bonds with the inner surface of the fullerene cage. It is found that the fullerene cage significantly increases the stability of the N₈ cube, but its lifetime at room temperature is insufficient to observe the endohedral complex N₈@C₆₀ without the use of extreme temperature conditions. It can be synthesized and investigated only at cryogenic temperatures.     

Bos d 13, A Novel Heat-Stable Beef Allergen

Scope

Red meat, a staple food of Western diets, can also induce IgE-mediated allergic reactions. Yet, apart from the heat-labile protein serum albumin and the carbohydrate α-Gal, the molecules causing allergic reactions to red meat remain unknown.

Methods and results

IgE reactivity profiles of beef-sensitized individuals are analyzed by IgE-immunoblotting with protein extracts from raw and cooked beef. Two IgE-reactive proteins are identified by peptide mass fingerprinting as myosinlight chain 1 (MYL1) and myosin light chain 3 (MYL3) in cooked beef extract and are designated Bos d 13 isoallergens. MYL1 and MYL3 are produced recombinantly in Escherichia coli. ELISAs proved their IgE reactivity and circular dichroism analysis showed that they represent folded molecules with remarkable thermal stability. In vitro gastrointestinal digestion experiments showed the higher stability of rMYL1 as compared to rMYL3. Exposure of a monolayer of Caco–2 cells to rMYL1 indicated that the molecule is able to cross intestinal epithelial cells without disturbing the integrity of the tight junctions, suggesting the sensitizing capacity of MYL1.

Conclusion

MYLs are identified as novel heat-stable bovine meat allergens.     

Microbiological stabilization of Aloe vera (Aloe barbadensis Miller) gel by high hydrostatic pressure treatment

The effect of high hydrostatic pressure (HHP) treatment (300, 400 and 500MPa for 1 and 3min at 20°C) on the microbiological shelf-life and microbiota composition of Aloe vera gel during 90days of storage at 4°C was investigated. Aerobic mesophilic and psychrotrophic bacteria, as well as moulds and yeasts, were enumerated after HHP treatment and through cold storage. Randomly selected isolates from the count plates were identified by standard methods and the API identification system. Results showed that HHP treatment at or over 400MPa for 3min were effective to keep the microbial counts to undetectable levels during the whole storage period, and consequently the microbiological shelf-life of A. vera gel was extended for more than 90days at 4°C. The microbiota in the untreated A. vera gel was dominated by Gram-negative bacteria (mostly Rahnella aquatilis) and yeasts (mostly Rhodotorula mucilaginosa). In contrast, Gram-positive bacteria tentatively identified as Arthrobacter spp. and Micrococcus/Kocuria spp. were the predominant microorganisms in samples pressurized at 300MPa for 1 and 3min, while Bacillus megaterium predominating in samples treated at 400MPa for 1min. At 400MPa for 3min and above, the microbial growth was completely suppressed during at least 90days; however, viable spore-formers were detected by enrichment.     

Pattern recognition of three Vitis vinifera L. red grapes varieties based on anthocyanin and flavonol profiles,with correlations between their biosynthesis pathways

The presence of anthocyanins and flavonols in three selected red grape varieties was investigated, in order to use their polyphenolic characterisation as a fingerprint. Berry skins of Gran Negro grapes were characterised by the presence of high content of malvidin- and peonidin-3-O-glucoside; Mouratón grapes, by the presence of high content of petunidin- and delphinidin-3-O-glucoside; and Brancellao grapes, by the presence of high content of cyanidin-3-O-glucoside. The main flavonols found included the 3-O-glucosides of quercetin, myricetin, kaempferol, laricitrin, isorhamnetin and syringetin. Using cluster analysis and principal components analysis, Gran Negro could be characterised by their content of isorhamnetin-3-O-glucoside and syringetin-3-O-glucoside and, along with Mouratón, by their myricetin conjugates. Flavonol profile could not provide a fingerprint of Brancellao variety. Stepwise discriminant analysis was performed in order to find the polyphenolic compounds, which characterised the selected grape varieties. Finally, anthocyanin and flavonol profiles in red grapes were compared and results confirmed that biosynthesis of flavonols is closely related to that of anthocyanins.     

Genotypic effects on the phytochemical quality of seeds and sprouts from commercial broccoli cultivars

Determining ontogenic diversity in vegetables, in general or Brassicas in particular, regarding the bioactive content, is an interesting task since the most promising Brassicaceae foods could have the highest nutritional and health-promoting properties. Therefore, vitamin C, phenolic compounds, glucosinolate content, and total antioxidant capacity were evaluated in commercial cultivars of broccoli (Brassica oleracea var. italica; cv. Nubia, cv. Marathon and cv. Viola) seeds and during the sprouting period. Vitamin C was not detected in dormant seeds and its content increased with the germination, reaching values ranging from 53 (cv. Nubia) to 64 (cv. Marathon) mg/100 g FW, at the end of the monitored period (14days). The total glucosinolate content in seeds and 3-day-old sprouts was higher in cv. Marathon (1005 and 556 mg/100 g FW, respectively), however cv. Viola sprouts registered the highest glucosinolate content 7 and 14 days after sowing (235 and 208 mg/100 g FW, respectively). Aliphatic glucosinolates were more affected by genetic factors than the indolic glucosinolates, being glucoraphanin the predominant glucosinolate in cv. Nubia and cv. Marathon, whereas glucoiberin was the major glucosinolate in cv. Viola. The flavonoid and total phenolic content was significantly higher in cv. Viola. Also, seeds of this cultivar showed the highest antioxidant capacity (2.7 mg Trolox/g FW).     

Enhanced Photoacoustic Beam Profiling of Pulsed Lasers

An improved version of a photoacoustic beam profiler of pulsed lasers is presented. The new model resorts to high-bandwidth condenser microphones to register higher-order, excited acoustic modes, thus enabling more accurate profiling. In addition, Xe was used as a buffer gas since its high atomic weight further reduces the eigenfrequencies. Furthermore, a new gas-handling system makes up for some deficiencies found in the first model. The system was calibrated using the Airy pattern generated with a pinhole illuminated by a frequency-doubled Nd:YAG laser that excited $\text{ NO }_{2}$ traces. Once calibrated, the beam profile of a TEA $\text{ CO }_{2}$ laser was obtained, using ethylene as the absorbing species. This profiler returns more accurate profiles than thermal paper.