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Cellulose nanofibers are extensively used in cosmetics, biomaterials, and aerodynamics industries. Providing several unique properties such as lightness, heat and pressure resistance. The key to engineering the applications of cellulose nanofibers lies within the molecular mechanism of the nanofibers arrangements to build higher order assemblies such as cellulose bundles. In this study, extensive atomistic molecular dynamics (MD) simulations, structural modeling and Scanning Electron Microscopy (SEM) approaches were used to explore the molecular mechanism of cellulose nanofibers arrangement. Four systems were explored in MD simulations including; two cellulose polymers of same length, two polymers where one is elongated, four polymers of same length and two planes consisting of four elongated polymers each. It was shown that the two polymers form a "cylindrical" arrangement regardless of their length. In this study the distance between the two polymers in the cylindrical structure is 3–5 Å. Upon elongation of the polymers, the arrangement becomes more stable. By increasing the number of polymers to four, a "plane" arrangement is formed.The distance between the polymers in such arrangement is 10-15 Å. Two planes that are built of elongated polymers maintain the plane arrangement as larger stacks. That are formed at a distance of 12–14 Å. A network of inter and intra fibers hydrogen bonds are the major interactions in formation and maintenance of these arrangements. Results of SEM shows that the polymer length does not alter the thickness of the nanofibers. Suggesting that the physical and mechanical properties of the fibers remain intact. Formation of the cylinder arrangement upon cross-linking of the fibers is stable. And by increasing the number of cylindrical units, the plane arrangement will be formed. This is the first comprehensive molecular mechanism of cellulose nanofibers arrangements at the atomic level. That could pave the path for further engineering of cellulose nanofibers for medical and industrial purposes. [ABSTRACT FROM AUTHOR]

EGFR and ErbB4 are the only two members of cancer-regulating ErbB RTKs that maintain the activation of their extracellular ligand-binding domain and intracellular tyrosine kinase domain. EGFR and ErbB4 could form homo and heterodimers upon their activation. Heterodimerization triggers more diverse intracellular pathways compared to homodimerization. Moreover, it is known that N-glycosylation is crucial for the stabilization and activation of EGFR and ErbB4 receptors. Herein, atomistic molecular dynamics were simulated to study the EGFR-ErbB4 heterodimer in the glycosylated and unglycosylated states. It was shown that the EGFR-ErbB4 heterodimer is highly stabilized by glycosylation. The increased stability is most significant at the dimeric interfaces, regulated by packing of three glycans attached to EGFR (Asn337) and ErbB4 (Asn333, Asn523) at the dimeric interface. Finally, it is proposed that heterodimerization is the persistent key player in the EGFR and ErbB4 activation. Thus, targeting the heterodimers in future therapeutic designs could be a promising approach against drug resistance to ErbB-positive cancers. [ABSTRACT FROM AUTHOR]

Milk thistle is an oil and medicinal crop known as an alternative oil crop with a high level of unsaturated fatty acids, which makes it a favorable edible oil for use in food production. To evaluate the importance of Milk thistle lipids in drought tolerance, an experiment was performed in field conditions under three different water deficit levels (Field capacity (FC), 70% FC and 40% FC). After harvesting seeds of the plant, their oily and methanolic extracts were isolated, and subsequently, types and amounts of lipids were measured using GC–MS. Genes and enzymes engaged in biosynthesizing of these lipids were identified and their expression in Arabidopsis was investigated under similar conditions. The results showed that content of almost all measured lipids of milk thistle decreased under severe drought stress, but genes (belonged to Arabidopsis), which were involved in their biosynthetic pathway showed different expression patterns. Genes biosynthesizing lipids, which had significant amounts were selected and their gene and metabolic network were established. Two networks were correlated, and for each pathway, their lipids and respective biosynthesizing genes were grouped together. Four up-regulated genes including PXG3, LOX2, CYP710A1, PAL and 4 down-regulated genes including FATA2, CYP86A1, LACS3, PLA2-ALPHA were selected. The expression of these eight genes in milk thistle was similar to Arabidopsis under drought stress. Thus, PXG3, PAL, LOX2 and CYP86A1 genes that increased expression were selected for protein analysis. Due to the lack of protein structure of these genes in the milk thistle, modeling homology was performed for them. The results of molecular docking showed that the four proteins CYP86A1, LOX2, PAL and PXG3 bind to ligands HEM, 11O, ACT and LIG, respectively. HEM ligand was involved in production of secondary metabolites and dehydration tolerance, and HEM binding site remained conserved in various plants. CA ligands were involved in synthesis of cuticles and waxes. Overall, this study confirmed the importance of lipids in drought stress tolerance in milk thistle. [ABSTRACT FROM AUTHOR]

ErbB family of receptor tyrosine kinases play significant roles in cellular differentiation and proliferation. Mutation or overexpression of these receptors leads to several cancers in humans. The family has four homologous members including EGFR, ErbB2, ErbB3, and ErbB4. From which all except the ErbB2 bind to growth factors via the extracellular domain to send signals to the cell. However, dimerization of the ErbB receptor occurs in extracellular, transmembrane, and intracellular domains. The ErbB receptors are known to form homodimers and heterodimers in the active form. Heterodimerization increases the variety of identified ligands and signaling pathways that can be activated by these receptors. Furthermore, glycosylation of the ErbB receptors has shown to be critical for their stability, ligand binding, and dimerization. Here, atomistic molecular dynamics simulations on the glycosylated and unglycosylated heterodimer showed that the EGFR-ErbB2 heterodimer is more stable in its dynamical pattern compared to the EGFR-EGFR homodimer. This increased stability is regulated by maintaining the dimeric interface by the attached glycans. It was also shown that the presence of various glycosylation sites within the ErbB2 growth factor binding site leads to occlusion of this site by the glycans that inhibit ligand binding to ErbB2 and participate in further stabilization of the heterodimer construct. Putting together, glycosylation seems to promote the heterodimer formation within the ErbB family members as the dominant molecular mechanism of activation for these receptors. [ABSTRACT FROM AUTHOR]

The development of artificial biocrust using cyanobacterium Phormidium tenue has been suggested as an effective strategy to prevent soil degradation. Here, a combination of in silico approaches with growth rate, photosynthetic pigment, morphology, and transcript analysis was used to identify specific genes and their protein products in response to 500 mM NaCl in P. tenue. The results show that 500 mM NaCl induces the expression of genes encoding glycerol-3-phosphate dehydrogenase (glpD) as a Flavoprotein, ribosomal protein S12 methylthiotransferase (rimO), and a hypothetical protein (sll0939). The constructed co-expression network revealed a group of abiotic stress-responsive genes. Using the Basic Local Alignment Search Tool (BLAST), the homologous proteins of rimO, glpD, and sll0939 were identified in the P. tenue genome. Encoded proteins of glpD, rimO, and DUF1622 genes, respectively, contain (DAO and DAO C), (UPF0004, Radical SAM and TRAM 2), and (DUF1622) domains. The predicted ligand included 22B and MG for DUF1622, FS5 for rimO, and FAD for glpD protein. There was no direct disruption in ligand-binding sites of these proteins by Na+, Cl−, or NaCl. The growth rate, photosynthetic pigment, and morphology of P. tenue were investigated, and the result showed an acceptable tolerance rate of this microorganism under salt stress. The quantitative real-time polymerase chain reaction (qRT-PCR) results revealed the up-regulation of glpD, rimO, and DUF1622 genes under salt stress. This is the first report on computational and experimental analyses of the glpD, rimO, and DUF1622 genes in P. tenue under salt stress to the best of our knowledge. [ABSTRACT FROM AUTHOR]

SARS-CoV-2 is a strain of Coronavirus family that caused the ongoing pandemic of COVID-19. Several studies showed that the glycosylation of virus spike (S) protein and the Angiotensin-Converting Enzyme 2 (ACE2) receptor on the host cell is critical for the virus infectivity. Molecular Dynamics (MD) simulations were used to explore the role of a novel mutated O-glycosylation site (D494S) on the Receptor Binding Domain (RBD) of S protein. This site was suggested as a key mediator of virus-host interaction. By exploring the dynamics of three O-glycosylated models and the control systems of unglcosylated S4944 and S494D complexes, it was shown that the decoration of S494 with elongated O-glycans results in stabilized interactions on the direct RBD-ACE2. Calculation of the distances between RBD and two major H1, H2 helices of ACE2 and the interacting pairs of amino acids in the interface showed that the elongated O-glycan maintains these interactions by forming several polar contacts with the neighbouring residues while it would not interfere in the direct binding interface. Relative binding free energy of RBD-ACE2 is also more favorable in the O-glycosylated models with longer glycans. The increase of RBD binding affinity to ACE2 depends on the size of attached O-glycan. By increasing the size of O-glycan, the RBD-ACE2 binding affinity will increase. Hence, this crucial factor must be taken into account for any further inhibitory approaches towards RBD-ACE2 interaction. [ABSTRACT FROM AUTHOR]