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The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the agent of a major global outbreak of respiratory tract disease known as Coronavirus Disease 2019 (COVID-19). SARS-CoV-2 infects mainly lungs and may cause several immune-related complications, such as lymphocytopenia and cytokine storm, which are associated with the severity of the disease and predict mortality. The mechanism by which SARS-CoV-2 infection may result in immune system dysfunction is still not fully understood. Here, we show that SARS-CoV-2 infects human CD4+ T helper cells, but not CD8+ T cells, and is present in blood and bronchoalveolar lavage T helper cells of severe COVID-19 patients. We demonstrated that SARS-CoV-2 spike glycoprotein (S) directly binds to the CD4 molecule, which in turn mediates the entry of SARS- CoV-2 in T helper cells. This leads to impaired CD4 T cell function and may cause cell death. SARS-CoV-2-infected T helper cells express higher levels of IL-10, which is associated with viral persistence and disease severity. Thus, CD4-mediated SARS-CoV-2 infection of T helper cells may contribute to a poor immune response in COVID-19 patients.

Carboxylesterases comprise a major class of α/β‐fold hydrolases responsible for the cleavage and formation of ester bonds. Found ubiquitously in nature, these enzymes are crucial for the metabolism of both endogenous and exogenous carboxyl esters in animals, plants and microorganisms. Beyond their essential physiological roles, carboxylesterases stand out as one of the important classes of biocatalysts for biotechnology. BlEst2, an enzyme previously classified as Bacillus licheniformis esterase, remains largely uncharacterized. In the present study, we elucidate the structural biology, molecular dynamics and biochemical features of BlEst2. Our findings reveal a canonical α/β‐hydrolase fold similar to the ESTHER block L of lipases, further augmented by two additional accessory C‐terminal domains. Notably, the catalytic domain demonstrates two insertions, which occupy conserved locations in α/β‐hydrolase proteins and commonly form the lid domain in lipase structures. Intriguingly, our in vitro cleavage of C‐terminal domains revealed the structure of the active form of BlEst2. Upon activation, BlEst2 showed a markedly elevated hydrolytic activity. This observation implies that the intramolecular C‐terminal domain serves as a regulatory intramolecular inhibitor. Interestingly, despite exhibiting esterase‐like activity, BlEst2 structural characteristics align more closely with lipases. This suggests that BlEst2 could potentially represent a previously unrecognized subgroup within the realm of carboxyl ester hydrolases. [ABSTRACT FROM AUTHOR]

GH10 xylanases and GH62 Arabinofuranosidases play key roles in the breakdown of arabinoxylans and are important tools in various industrial and biotechnological processes, such as renewable biofuel production, the paper industry, and the production of short-chain xylooligosaccharides (XOS) from plant biomass. However, the use of these enzymes in industrial settings is often limited due to their relatively low thermostability and reduced catalytic efficiency. To overcome these limitations, strategies based on enzymatic chimera construction and the use of metal ions and other cofactors have been proposed to produce new recombinant enzymes with improved catalytic activity and thermostability. Here, we examine the conformational dynamics of a GH10-GH62 chimera at different calcium ion concentrations through molecular dynamics simulations. While experimental data have demonstrated improved activity and thermostability in GH10-GH62 chimera, the mechanistic basis for these enhancements remains unclear. We explored the structural details of the binding subsites of Ca2+ in the parental enzymes GH62 from Aspergillus fumigatus (Afafu62) and a recombinant GH10 from Cryptococcus flavescens (Xyn10cf), as well as their chimeric combination, and how negatively charged electron pairing located at the protein surface affects Ca2+ capture. The results indicate that Ca2+ binding significantly contributes to structural stability and catalytic cavity modulation in the chimera, particularly evident at a concentration of 0.01 M. This effect, not observed in the parental GH10 and GH62 enzymes, highlights how Ca2+ enhances stability in the overall chimeric enzyme, while supporting a larger cavity volume in the chimera GH62 subunit. The increased catalytic site volume and reduced structural flexibility in response to Ca2+ suggest that calcium binding minimizes non-productive conformational states, which could potentially improve catalytic turnover. The findings presented here may aid in the development of more thermostable and efficient catalytic systems. [ABSTRACT FROM AUTHOR]

Zong and coworkers combine computational and experimental methods to decipher in detail the mechanism of action of glucuronoyl esterases, enzymes with significant biotechnological potential for decoupling lignin from polysaccharides in biomass.

Microbial aromatic catabolism offers a promising approach to convert lignin, a vast source of renewable carbon, into useful products. Aryl-O-demethylation is an essential biochemical reaction to ultimately catabolize coniferyl and sinapyl lignin-derived aromatic compounds, and is often a key bottleneck for both native and engineered bioconversion pathways. Here, we report the comprehensive characterization of a promiscuous P450 aryl-O-demethylase, consisting of a cytochrome P450 protein from the family CYP255A (GcoA) and a three-domain reductase (GcoB) that together represent a new two-component P450 class. Though originally described as converting guaiacol to catechol, we show that this system efficiently demethylates both guaiacol and an unexpectedly wide variety of lignin-relevant monomers. Structural, biochemical, and computational studies of this novel two-component system elucidate the mechanism of its broad substrate specificity, presenting it as a new tool for a critical step in biological lignin conversion.

Using machine learning, molecular dynamics simulations, and density functional theory calculations we gain insight into the selectivity patterns of substrate activation by the cytochromes P450. In nature, the reactions catalyzed by the P450s lead to the biodegradation of xenobiotics, but recent work has shown that fungi utilize P450s for the activation of lignin fragments, such as monomer and dimer units. These fragments often are the building blocks of valuable materials, including drug molecules and fragrances, hence a highly selective biocatalyst that can produce these compounds in good yield with high selectivity would be an important step in biotechnology. In this work a detailed computational study is reported on two reaction channels of two P450 isozymes, namely the O-deethylation of guaethol by CYP255A and the O-demethylation versus aromatic hydroxylation of p-anisic acid by CYP199A4. The studies show that the second-coordination sphere plays a major role in substrate binding and positioning, heme access, and in the selectivity patterns. Moreover, the local environment affects the kinetics of the reaction through lowering or raising barrier heights. Furthermore, we predict a site-selective mutation for highly specific reaction channels for CYP199A4. [ABSTRACT FROM AUTHOR]

A home-made column (3.2 mm i.d., 100 mm length) was prepared in which glycidyl polymethacrylate was used. The optimum value of the initiator corresponded to 5 mg/mL. The column morphology was characterized by scanning electron microscopy. The permeability was evaluated using acetonitrile and water as a mobile phase and uracil as an unretained substrate. A simple and economical reversed-phase HPLC method has been developed for the simultaneous estimation of paracetamol and chlorzoxazone in their pharmaceutical formulations. Components were determined using a UV detector at 270 nm. The mobile phase was composed of 1% formic acid solution and acetonitrile (65/35, v/v); 0.7 mL/min flow rate and 5.0 [micro]L injection volume were used. Peak resolution was 1.96. All findings allow concluding that the prepared stainless steel conventional HPLC column and the novel validated method are applicable for quality control and routine analysis., Author(s): Mutaz E. Salih [sup.1] [sup.2], Ahmad Aqel [sup.3], Babiker Y. Abdulkhair [sup.1] [sup.4], Munir S. Obbed [sup.3], Zeid A. ALOthman [sup.3], Yacine Badjah-Hadj-Ahmed [sup.3], Mohamad A. Abdulaziz [sup.1] Author [...]

The metrological quality of a measurement is characterised by evaluating the uncertainty in the measurement. In this paper, uncertainty in personal dose measured using individual monitoring CaSO4:Dy-based thermoluminescence dosimeter badge is evaluated by application of the guide to the expression of uncertainty in measurement method. The present dose reporting quantity, whole body dose (WBD) and the proposed quantity, personal dose equivalent, H p(10) has been used as measurands. The influence of various input quantities on the measurement were analyzed through tests that conform to the requirements of the International Electrotechnical Commission IEC 62387. The study found that the expanded uncertainties for WBD and H p(10) measurements were 63.4% and 41.4%, respectively, corresponding to a 95% coverage probability for workplace fields covering a wide photon energy range (33–1250 keV). However, the uncertainty estimates were quite lower for the type of workplaces that are identified using the dose evaluation algorithm. The input quantities, namely, the response to a mixture of photon beam qualities and photon energy and angular dependence contribute the most to the total uncertainty. [ABSTRACT FROM AUTHOR]

Shabir Ahmad,1 Sidra Munir,1 Nadia Zeb1,2 Asad Ullah,1 Behramand Khan,1 Javed Ali,3 Muhammad Bilal,3 Muhammad Omer,4 Muhammad Alamzeb,5 Syed Muhammad Salman,1 Saqib Ali51Department of Chemistry, Islamia College University, Peshawar 25120, Pakistan; 2Department of Chemistry, Government Girls Degree College, Peshawar, Pakistan; 3Department of Chemistry, Kohat University of Science and Technology, Kohat, Pakistan; 4Institute of Chemical Sciences, University of Swat, Swat, 19201, Pakistan; 5Department of Chemistry, University of Kotli 11100, Azad Jammu and Kashmir, PakistanBackground: Nanotechnology explores a variety of promising approaches in the area of material sciences on a molecular level, and silver nanoparticles (AgNPs) are of leading interest in the present scenario. This review is a comprehensive contribution in the field of green synthesis, characterization, and biological activities of AgNPs using different biological sources.Methods: Biosynthesis of AgNPs can be accomplished by physical, chemical, and green synthesis; however, synthesis via biological precursors has shown remarkable outcomes. In available reported data, these entities are used as reducing agents where the synthesized NPs are characterized by ultraviolet-visible and Fourier-transform infrared spectra and X-ray diffraction, scanning electron microscopy, and transmission electron microscopy.Results: Modulation of metals to a nanoscale drastically changes their chemical, physical, and optical properties, and is exploited further via antibacterial, antifungal, anticancer, antioxidant, and cardioprotective activities. Results showed excellent growth inhibition of the microorganism.Conclusion: Novel outcomes of green synthesis in the field of nanotechnology are appreciable where the synthesis and design of NPs have proven potential outcomes in diverse fields. The study of green synthesis can be extended to conduct the in silco and in vitro research to confirm these findings.Keywords: green synthesis, plant mediated synthesis, silver bioactivity, microorganism