New Insights into the Cooperativity and Dynamics of Dimeric Enzymes.

A survey of protein databases indicates that the majority of enzymes exist in oligomeric forms, with about half of those found in the UniProt database being homodimeric. Understanding why many enzymes are in their dimeric form is imperative. Recent developments in experimental and computational techniques have allowed for a deeper comprehension of the cooperative interactions between the subunits of dimeric enzymes. This review aims to succinctly summarize these recent advancements by providing an overview of experimental and theoretical methods, as well as an understanding of cooperativity in substrate binding and the molecular mechanisms of cooperative catalysis within homodimeric enzymes. Focus is set upon the beneficial effects of dimerization and cooperative catalysis. These advancements not only provide essential case studies and theoretical support for comprehending dimeric enzyme catalysis but also serve as a foundation for designing highly efficient catalysts, such as dimeric organic catalysts. Moreover, these developments have significant implications for drug design, as exemplified by Paxlovid, which was designed for the homodimeric main protease of SARS-CoV-2.

Genome-wide identification of potential odontogenic genes involved in the dental epithelium-mesenchymal interaction during early odontogenesis.

BACKGROUND: Epithelium-mesenchymal interactions are involved in odontogenic processes. Previous studies have focused on the intracellular signalling regulatory network in tooth development, but the functions of extracellular regulatory molecules have remained unclear. This study aims to explore the gene profile of extracellular proteoglycans and their glycosaminoglycan chains potentially involved in dental epithelium-mesenchymal interactions using high-throughput sequencing to provide new understanding of early odontogenesis. RESULTS: Whole transcriptome profiles of the mouse dental epithelium and mesenchyme were investigated by RNA sequencing (RNA-seq). A total of 1,281 and 1,582 differentially expressed genes were identified between the dental epithelium and mesenchyme at E11.5 and E13.5, respectively. Enrichment analysis showed that extracellular regions and ECM-receptor interactions were significantly enriched at both E11.5 and E13.5. Polymerase chain reaction analysis confirmed that the extracellular proteoglycan family exhibited distinct changes during epithelium-mesenchymal interactions. Most proteoglycans showed higher transcript levels in the dental mesenchyme, whereas only a few were upregulated in the epithelium at both stages. In addition, 9 proteoglycans showed dynamic expression changes between these two tissue compartments. Gpc4, Sdc2, Spock2, Dcn and Lum were expressed at higher levels in the dental epithelium at E11.5, whereas their expression was significantly higher in the dental mesenchyme at E13.5, which coincides with the odontogenic potential shift. Moreover, the glycosaminoglycan biosynthetic enzymes Ext1, Hs3st1/5, Hs6st2/3, Ndst3 and Sulf1 also exhibited early upregulation in the epithelium but showed markedly higher expression in the mesenchyme after the odontogenic potential shift. CONCLUSION: This study reveals the dynamic expression profile of extracellular proteoglycans and their biosynthetic enzymes during the dental epithelium-mesenchymal interaction. This study offers new insight into the roles of extracellular proteoglycans and their distinct sulfation underlying early odontogenesis.

FAM20B-catalyzed glycosaminoglycans control murine tooth number by restricting FGFR2b signaling.

BACKGROUND: The formation of supernumerary teeth is an excellent model for studying the molecular mechanisms that control stem/progenitor cell homeostasis needed to generate a renewable source of replacement cells and tissues. Although multiple growth factors and transcriptional factors have been associated with supernumerary tooth formation, the regulatory inputs of extracellular matrix in this regenerative process remains poorly understood. RESULTS: In this study, we present evidence that disrupting glycosaminoglycans (GAGs) in the dental epithelium of mice by inactivating FAM20B, a xylose kinase essential for GAG assembly, leads to supernumerary tooth formation in a pattern reminiscent of replacement teeth. The dental epithelial GAGs confine murine tooth number by restricting the homeostasis of Sox2(+) dental epithelial stem/progenitor cells in a non-autonomous manner. FAM20B-catalyzed GAGs regulate the cell fate of dental lamina by restricting FGFR2b signaling at the initial stage of tooth development to maintain a subtle balance between the renewal and differentiation of Sox2(+) cells. At the later cap stage, WNT signaling functions as a relay cue to facilitate the supernumerary tooth formation. CONCLUSIONS: The novel mechanism we have characterized through which GAGs control the tooth number in mice may also be more broadly relevant for potentiating signaling interactions in other tissues during development and tissue homeostasis.

Low energy consumption vortex wave flow membrane bioreactor.

In order to reduce the energy consumption and membrane fouling of the conventional membrane bioreactor (MBR), a kind of low energy consumption vortex wave flow MBR was exploited based on the combination of biofilm process and membrane filtration process, as well as the vortex wave flow technique. The experimental results showed that the vortex wave flow state in the membrane module could be formed when the Reynolds number (Re) of liquid was adjusted between 450 and 1,050, and the membrane flux declined more slowly in the vortex wave flow state than those in the laminar flow state and turbulent flow state. The MBR system was used to treat domestic wastewater under the condition of vortex wave flow state for 30 days. The results showed that the removal efficiency for CODcr and NH3-N was 82% and 98% respectively, and the permeate quality met the requirement of 'Water quality standard for urban miscellaneous water consumption (GB/T 18920-2002)'. Analysis of the energy consumption of the MBR showed that the average energy consumption was 1.90 ± 0.55 kWh/m3 (permeate), which was only two thirds of conventional MBR energy consumption.

Magnetic field assisted preparation of PES-Ni@MWCNTs membrane with enhanced permeability and antifouling performance.

Multiple wall carbon nanotubes (MWCNTs), as an excellent material, have been used in various applications including preparation of polymer-MWCNTs composite membranes. However, few reports have combined the magnetic Ni@MWCNTs with polyether sulfone (PES) membrane to improve its antifouling performance to humic acid (HA), sodium alginate (SA), bovine serum albumin (BSA) and yeast (YE) solutions. In this study, the Ni@MWCNTs was generated by immersing MWCNTs into Ni2+ solution where in-situ reduction reaction was launched by the adsorbed Ag+ on MWCNTs. Since the loaded Ni endowed magnetism to MWCNTs, the Ni@MWCNTs can be easily attracted onto the membrane surface by an external magnetic field during the phase inversion process. The morphology measurements confirmed that the Ni@MWCNTs headed out of the PES-Ni@MWCNTs membrane surface. Because the MWCNTs played a role of free channels for water molecules, the composite membrane water flux reached to threefold flux of the pristine membrane. Moreover, the PES-Ni@MWCNTs membranes displayed the obviously enhanced antifouling ability during all the three alternative filtration cycles of water and BSA, SA, YE and HA solutions. In addition, the optimal PES-Ni@MWCNTs membrane demonstrated a flux recovery rate (FRR) of 67.89%, 85.53%, 60.28 and 90.12% for BSA, SA, YE and HA, respectively, which were not only much higher than that of the pristine membrane, but also exhibited significant improvements comparing with the previous studies. Further results of extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory indicated that the modified membrane possessed advantageous interaction energies with contaminant molecules over the pristine membrane.

The spatiotemporal expression pattern of Syndecans in murine embryonic teeth.

The hierarchical interactions between the dental epithelium and dental mesenchyme represent a common paradigm for organogenesis. During tooth development, various morphogens interact with extracellular components in the extracellular matrix and on the cell surfaces to transmit regulatory signaling into cells. We recently found pivotal roles of FAM20B-catalyzed proteoglycans in the control of murine tooth number at embryonic stages. However, the expression pattern of proteoglycans in embryonic teeth has not been well understood. We extracted total RNA from E14.5 murine tooth germs for semi-quantitative RT-PCR analysis of 29 proteoglycans, and identified 23 of them in the embryonic teeth. As a major subfamily of FAM20B-catalyzed proteoglycans, Syndecans are important candidates being potentially involved in the tooth development of mice. We examined the expression pattern of Syndecans in embryonic teeth using in situ hybridization (ISH) and immunohistochemistry (IHC) approaches. Syndecan-1 is mainly present in the dental mesenchyme at early embryonic stages. Subsequently, its expression expands to both dental epithelium and dental mesenchyme. Syndecan-2 is strongly expressed in the dental mesenchyme at early embryonic stages, then shifts to the stratum intermedium and inner dental epithelium at cap stages. Syndecan-3 shows a gradually increased expression that initially in the dental epithelium of both incisors and molars and then in the inner dental epithelium and stratum intermedium in molars alone. Syndecan-4 is localized in the dental epithelium in incisors and the dental follicle mesenchyme in molars at early cap stage. The spatiotemporal expression pattern of Syndecans in murine embryonic teeth suggest potential roles of these proteoglycans in murine tooth morphogenesis.

Dual-Functional Dextran-PEG Hydrogel as an Antimicrobial Biomedical Material.

Microbial infections continually present a major worldwide public healthcare threat, particularly in instances of impaired wound healing and biomedical implant fouling. The development of new materials with the desired antimicrobial property to avoid and treat wound infection is urgently needed in wound care management. This study reports a novel dual-functional biodegradable dextran-poly(ethylene glycol) (PEG) hydrogel covalently conjugated with antibacterial Polymyxin B and Vancomycin (Vanco). The hydrogel is designed as a specialized wound dressing that eradicates existing bacteria and inhibits further bacteria growth, while, ameliorating the side effects of antibiotics and accelerating tissue repair and regeneration. The hydrogel exhibits potent antibacterial activities against both gram-negative bacteria Escherichia coli (E. coli) and gram-positive bacteria Staphylococcus aureus (S. aureus) with no observable toxicity to mouse fibroblast cell line NIH 3T3. These results demonstrate the immense potential of dextran-PEG hydrogel as a wound dressing healthcare material in efficiently controlling bacteria growth in complex biological systems.