Recent Progress in Thermoplastic Polyurethane/MXene Nanocomposites: Preparation, Flame-Retardant Properties and Applications.

MXene, a promising two-dimensional nanomaterial, exhibits significant potential across various applications due to its multilayered structure, metal-like conductivity, solution processability, and surface functionalization capabilities. These remarkable properties facilitate the integration of MXenes and MXene-based materials into high-performance polymer composites. Regarding this, a comprehensive and well-structured up-to-date review is essential to provide an in-depth understanding of MXene/thermoplastic polyurethane nanocomposites. This review discusses various synthetic and modification methods of MXenes, current research progress and future potential on MXene/thermoplastic polyurethane nanocomposites, existing knowledge gaps, and further development. The main focus is on discussing strategies for modifying MXene-based compounds and their flame-retardant efficiency, with particular emphasis on understanding their mechanisms within the TPU matrix. Ultimately, this review addresses current challenges and suggests future directions for the practical utilization of these materials.

Recent Progress in Two-Dimensional Nanomaterials for Flame Retardance and Fire-Warning Applications.

Graphene-like 2D nanomaterials, such as graphene, MXene, molybdenum disulfide, and boron nitride, present a promising avenue for eco-friendly flame retardants. Their inherent characteristics, including metal-like conductivity, high specific surface area, electron transport capacity, and solution processability, make them highly suitable for applications in both structural fire protection and fire alarm systems. This review offers an up-to-date exploration of advancements in flame retardant composites, utilizing pristine graphene-like nanosheets, versatile graphene-like nanosheets with multiple functions, and collaborative systems based on these nanomaterials. Moreover, graphene-like 2D nanomaterials exhibit considerable potential in the development of early fire alarm systems, enabling timely warnings. This review provides an overview of flame-retarding and fire-warning mechanisms, diverse multifunctional nanocomposites, and the evolving trends in the development of fire alarm systems anchored in graphene-like 2D nanomaterials and their derivatives. Ultimately, the existing challenges and prospective directions for the utilization of graphene-like 2D nanomaterials in flame retardant and fire-warning applications are put forward.

Advancements in Flame-Retardant Systems for Rigid Polyurethane Foam.

The amplified employment of rigid polyurethane foam (RPUF) has accentuated the importance of its flame-retardant properties in stimulating demand. Thus, a compelling research report is essential to scrutinize the recent progression in the field of the flame retardancy and smoke toxicity reduction of RPUF. This comprehensive analysis delves into the conventional and innovative trends in flame-retardant (FR) systems, comprising reactive-type FRs, additive-type FRs, inorganic nanoparticles, and protective coatings for flame resistance, and summarizes their impacts on the thermal stability, mechanical properties, and smoke toxicity suppression of the resultant foams. Nevertheless, there are still several challenges that require attention, such as the migration of additives, the insufficient interfacial compatibility between flame-retardant polyols or flame retardants and the RPUF matrix, and the complexity of achieving both flame retardancy and mechanical properties simultaneously. Moreover, future research should focus on utilizing functionalized precursors and developing biodegradable RPUF to promote sustainability and to expand the applications of polyurethane foam.

Amplectobeluid Radiodont Guanshancaris gen. nov. from the Lower Cambrian (Stage 4) Guanshan Lagerstätte of South China: Biostratigraphic and Paleobiogeographic Implications.

Radiodonta, an extinct stem-euarthropod group, has been considered as the largest predator of Cambrian marine ecosystems. As one of the radiodont-bearing Konservat-Lagerstätten, the Guanshan biota (South China, Cambrian Stage 4) has yielded a diverse assemblage of soft-bodied and biomineralized taxa that are exclusive to this exceptional deposit. "Anomalocaris" kunmingensis, the most abundant radiodont in the Guanshan biota, was originally assigned to Anomalocaris within the Anomalocarididae. Despite this taxon being formally assigned to the family Amplectobeluidae more recently, its generic assignment remains uncertain. Here, we present new materials of "Anomalocaris" kunmingensis from the Guanshan biota, and reveal that the frontal appendages possess two enlarged endites; all endites bear one posterior auxiliary spine and up to four anterior auxiliary spines; three robust dorsal spines and one terminal spine protrude from the distal part. These new observations, allied with anatomical features illustrated by previous studies, allow us to assign this taxon to a new genus, Guanshancaris gen. nov. Brachiopod shell bearing embayed injury and incomplete trilobites, associated with frontal appendages in our specimens, to some extent confirm Guanshancaris as a possible durophagous predator. The distribution of amplectobeluids demonstrates that this group is restricted to Cambrian Stage 3 to Drumian, and occurs across South China and Laurentia within the tropics/subtropics belt. Moreover, the amount and abundance of amplectobeluids evidently decreases after the Early-Middle Cambrian boundary, which indicates its possible preference for shallow water, referring to its paleoenvironmental distribution and may be influenced by geochemical, tectonic, and climatic variation.

ADP-Induced Conformational Transition of Human Adenylate Kinase 1 Is Triggered by Suppressing Internal Motion of α3α4 and α7α8 Fragments on the ps-ns Timescale.

Human adenylate kinase 1 (hAK1) plays a vital role in the energetic and metabolic regulation of cell life, and impaired functions of hAK1 are closely associated with many diseases. In the presence of Mg2+ ions, hAK1 in vivo can catalyze two ADP molecules into one ATP and one AMP molecule, activating the downstream AMP signaling. The ADP-binding also initiates AK1 transition from an open conformation to a closed conformation. However, how substrate binding triggers the conformational transition of hAK1 is still unclear, and the underlying molecular mechanisms remain elusive. Herein, we determined the solution structure of apo-hAK1 and its key residues for catalyzing ADP, and characterized backbone dynamics characteristics of apo-hAK1 and hAK1-Mg2+-ADP complex (holo-hAK1) using NMR relaxation experiments. We found that ADP was primarily bound to a cavity surrounded by the LID, NMP, and CORE domains of hAK1, and identified several critical residues for hAK1 catalyzing ADP including G16, G18, G20, G22, T39, G40, R44, V67, D93, G94, D140, and D141. Furthermore, we found that apo-hAK1 adopts an open conformation with significant ps-ns internal mobility, and Mg2+-ADP binding triggered conformational transition of hAK1 by suppressing the ps-ns internal motions of α3α4 in the NMP domain and α7α8 in the LID domain. Both α3α4 and α7α8 fragments became more rigid so as to fix the substrate, while the catalyzing center of hAK1 experiences promoted µs-ms conformational exchange, potentially facilitating catalysis reaction and conformational transition. Our results provide the structural basis of hAK1 catalyzing ADP into ATP and AMP, and disclose the driving force that triggers the conformational transition of hAK1, which will deepen understanding of the molecular mechanisms of hAK1 functions.

Suramin Targets the Conserved Ligand-Binding Pocket of Human Raf1 Kinase Inhibitory Protein.

Suramin was initially used to treat African sleeping sickness and has been clinically tested to treat human cancers and HIV infection in the recent years. However, the therapeutic index is low with numerous clinical side-effects, attributed to its diverse interactions with multiple biological macromolecules. Here, we report a novel binding target of suramin, human Raf1 kinase inhibitory protein (hRKIP), which is an important regulatory protein involved in the Ras/Raf1/MEK/ERK (MAPK) signal pathway. Biolayer interference technology showed that suramin had an intermediate affinity for binding hRKIP with a dissociation constant of 23.8 µM. Both nuclear magnetic resonance technology and molecular docking analysis revealed that suramin bound to the conserved ligand-binding pocket of hRKIP, and that residues K113, W173, and Y181 play crucial roles in hRKIP binding suramin. Furthermore, suramin treatment at 160 µM could profoundly increase the ERK phosphorylation level by around 3 times. Our results indicate that suramin binds to hRKIP and prevents hRKIP from binding with hRaf1, thus promoting the MAPK pathway. This work is beneficial to both mechanistically understanding the side-effects of suramin and efficiently improving the clinical applications of suramin.

Recombinant expression, biophysical and functional characterization of ClpS from Mycobacterium tuberculosis.

Intracellular proteolysis is attracting more and more attention for its unique and important character in Mycobacterium tuberculosis (Mt). The ClpS protein from Mt (MtClpS) plays a critical role in intracellular proteolysis by recognizing N-end rule substrates, which makes it become a potential target for antibacterial drugs. However, the molecular mechanism of MtClpS recognizing N-end rule substrates remains unclear. Preparation of highly concentrated and pure MtClpS protein is a prerequisite for further structural and functional studies. In the present work, we tried several fusion tags and various expression conditions to maximize the production of MtClpS in Escherichia coli. We established an efficient approach for preparing the MtClpS protein with a high yield of 24.7 mg/l and a high purity of 98%. After buffer screening, we obtained a stable MtClpS protein sample concentrated at 0.63 mM in the presence of glycerol, l-Arginine, and l-Glutamate. Moreover, circular dichroism characterization indicated that the secondary structure of MtClpS consists of 38% α-helix and 24% ß-sheet. The 2D 1H-15N HSQC nuclear magnetic resonance spectrum showed a good dispersion of resonance peaks with uniform intensity, indicating that the purified MtClpS protein was well folded and conformationally homogeneous. Isothermal titration calorimetry experiments revealed significant interactions of MtClpS with N-end rule peptides beginning with Leu, Tyr, Trp, or Phe. Furthermore, residues D34, D35, and H66 were confirmed as key residues for MtClpS recognizing the N-end rule peptide. The successful expression and biophysical characterization of MtClpS enabled us to gain insight into the molecular mechanism of MtClpS recognizing N-end rule substrates. The obtained stable and pure recombinant MtClpS will enable future inhibitor screening experiments.

A highly ordered honeycomb-like nickel(III/II) oxide-enhanced photocatalytic fuel cell for effective degradation of bisphenol A.

The honeycomb-like nickel(III/II) oxide interpenetrated framework arrays labelled as H-NiOx are used as cathode catalysts for the degradation of bisphenol A (BPA) in visible light-excited fuel cells. The nanoparticle close-packed NiOx aggregates (C-NiOx) and H-NiOx are prepared by conventional electrodeposition (ED) and advanced oxidation-associated electrodeposition (AO-ED) strategies, carried out by multiple voltammetry controlled in the potential ranges of 0 to -1.3 V and 1.3 to -1.3 V (vs. SCE), respectively. Compared with C-NiOx, the H-NiOx frameworks with smaller charge transfer resistance and higher surface-confined redox-active centers exhibit larger cathode electrocatalytic activity for the photocatalytic degradation of BPA. The NaClO can act as a sacrificial agent to sustain the integrity and stability of H-NiOx cathode. The H-NiOx-assisted BPA degradation conditions are optimized by changing process variables. The BPA is degraded by 48.5% within 120 min in photocatalytic BPA (1.0 mmol L-1, pH 13) fuel cell employing H-NiOx cathode, CdS/TiO2 photoanode and 0.2 mol L-1 NaClO catholyte, and its degradation rate conforms to the first-order reaction kinetic model. The H-NiOx can remarkably enhance the performances of the photocatalytic fuel cell, achieving a 4.1-fold or 15.2-fold increase in the short circuit current and maximum power density compared with that using bare cathode.

The migration speed of cancer cells influenced by macrophages and myofibroblasts co-cultured in a microfluidic chip.

We employ a microfluidic chip with three culture chambers to investigate the interactions among lung cancer cells, macrophages and myofibroblasts. By mixing the conditioned media of macrophages and myofibroblasts in this chip, we confirm that these two stromal cells have synergistic effects in accelerating the migration of cancer cells. However, as the myofibroblasts are pretreated with the conditioned medium of macrophages, the myofibroblasts' ability to enhance the migration of cancer cells is lowered. The tumour necrosis factor-α produced by macrophages reduces the expression of α-smooth muscle actin and the secretion of transforming growth factor-ß1 in myofibroblasts. Once the tumour necrosis factor-α in the macrophage conditioned medium is neutralized, the macrophage medium-pretreated myofibroblasts can still accelerate the migration of cancer cells.