Search Results (3,449)

We cross-linked unfractionated heparin (H) using epichlorohydrin (E), in the absence or presence of imidazole (I), using various ratios of H, E, and I substances. The objectives and goals were to use the reaction for the preparation of medical materials suitable for blood sample applications. Nuclear magnetic resonance indicated the involvement of an H-end sequence [H-(1→4)-β-D-GlcA-(1→3)-β-D-Gal-(1→3)-β-D-Gal-(1→4)-β-D-Xyl-α-Ser] in the linkage with the 2-hydroxypropyl bridge. The yields of the individual experiments were found to increase in the following ratios: 1H/1E/3I (24%) < 1H/1E/2I (32%) < 1H/3E (42%) < 1H/1E/1I (46%) < 1H/2E (64%) < 1H/1E (77%). According to size-exclusion chromatography with multiple-angle light scattering (SEC-MALS) analysis, the mass at the peak increased in the following order: H (9292 g/mol) < 1H/1E (9294 g/mol) < 1H/2E (9326 g/mol) < 1H/3E (9708 g/mol) < 1H/1E/2I (11,212 g/mol) < 1H/1E/3I (12,301 g/mol) < 1H/1E/1I (13,800 g/mol) and in the reverse order with the increase in amount of epichlorohydrin and imidazole, i.e., 1H/1E > 1H/2E > 1H/3E and 1H/1E/1I > 1H/1E/2I > 1H/1E/3I. X-ray diffraction revealed that all prepared films were amorphous. An evaluation of the surface morphology using atomic force microscopy (AFM) confirmed a relatively low films roughness (~0.9–3.6 nm). The surface reduced elastic modulus, determined by the PeakForce quantitative nanomechanical mapping (PF-QNM) technique, was found to increase by up to ~63% for films cross-linked with E in the absence of I when compared with the results for the H substrate. A negligible change in modulus was, however, observed for films cross-linked in the presence of I, or was even reduced by ~15% (1H/1E/3I) compared to that for the H substrate. This could be explained by the parallel cross-linking of H only with E within its serine end unit and in competition with only one nitrogen of I. According to the highest yield (77%) of 1H/1E, the preferred product is the following: H-(1→4)-β-D-GlcA-(1→3)-β-D-Gal-(1→3)-β-D-Gal-(1→4)-β-D-Xyl-α-Ser-CH₂-CH(OH)-CH₂-OH. For the 1H/1E/1I (46% yield), 1H/1E/2I (32%), and 1H/1E/3I (24%) products, the cross-linked motif was the same, and the difference represented the surplus amount of the imidazolium cation ionically bound to the heparin anionic groups. Full article

Schiff base reactions are widely used in pharmacy, catalysis, and volatile aldehyde detection. However, common biomarker sensing methods struggle to monitor this reaction process precisely due to their sensitivity, their time-consuming nature, and complex substrates. Here, we introduce the Nanoparticle-on-Mirror structure for in situ monitoring this reaction process through the application of a Au nanoparticle-p-Aminothiophenol-Au thin-film platform by surface-enhanced Raman scattering (SERS). Owing to the exposure of -NH₂ groups and the local ultra-strong electromagnetic field in the nanocavity, the Schiff base reactions process can be rapidly monitored within two minutes. Meanwhile, the monitoring platform can detect benzaldehyde molecules as low as 10⁻⁶ M, showing excellent SERS performance. Notably, the Au-nanoparticle-p-Aminothiophenol-Au thin-film platform exhibited anti-interference and specificity, being able to identify BA in the presence of interference. The use of the Au-nanoparticle-p-Aminothiophenol-Au thin-film platform provides a sensing method for Schiff base reactions with accuracy and simplicity of operation, achieving a balanced approach for low-cost and high-performance real-time monitoring, which is expected to be applied in various catalytic reaction process monitoring and catalyst design processes. Full article

In addition to the course of over 20 years of cucurbit-7-uril (CB[7]) in the pharmaceutical industry, the present study brings together the most recent observations from the perspective of ultrasensitive Raman spectroscopy and Density Functional Theory (DFT) related to the interaction of this molecule with atenolol (Ate) enantiomers during the formation of these host–guest complexes. Quantum chemistry calculations based on DFT were first used to understand the interaction geometry between CB[7] and Ate. These results were further confirmed by ultrasensitive vibrational spectroscopy. The spectral features associated with each enantiomer in the presence of CB[7] were analyzed by means of SERS, highlighting distinct interaction profiles. These experimental findings validated quantum chemical calculations, offering a comprehensive understanding of the host–guest interactions at the nanoscale level. Full article

This article presents an examination of well-controlled patterns created using a Ga⁺-based focused ion beam (FIB) on glass, while silicon substrates were used to evaluate the FIB performance by its achievable feature size versus time constraints. The pattern creation on glass was developed with the aim of studying potential surface-enhanced Raman spectroscopy (SERS) applications. Furthermore, the FIB was used to create dimer systems of periodically and randomly positioned dumbbell-shaped pits on the glass (each dimer occupies an area of 203 × 87 nm²). By following the bitmap pattern files, the FIB ensured there was 3000 dimer fabrication over a 20 × 20 μm² large area, with a pit size and position variation below 10 nm. The article highlights that FIB can be used for precise large-area nano-fabrication. The gold nanoparticle dimers were formed on the prepatterned surface via capillary force-assisted deposition. The fabricated nanostructures were tested in SERS measurements. The enhancement factor for Rhodamine B molecule reached ~10⁵, demonstrating the potential application of the method to create nanostructures in the sensor domain. Full article

Surface-enhanced Raman scattering (SERS) is widely used for trace detection of substances, and the key to this technology lies in the preparation of the substrate material. In this study, a composite SERS material of Au NRs/4-MBA/PAM was constructed and characterized to better immobilize the reference molecule 4-mercaptobenzoic acid (4-MBA). Electron transmission microscopy results demonstrated that the PAM film helps Au NRs to pack closely, enhancing the stability of the material structure and reducing the interference of external environmental factors on the response of 4-MBA, thus improving the accuracy of quantitative determination. Comparative experimental results with the Au NRs/4-MBA substrate showed that the relative standard deviations (RSDs) of the detection results for MG on different batches of Au NRs/4-MBA/PAM were less than 8.0%, and the RSDs of different points on the same material were less than 10.0%, indicating that the Au NRs/4-MBA/PAM has higher uniformity, better reproducibility, and higher sensitivity in detecting malachite green (MG). Applying this material in the recovery determination of fish extract showed that the recovery rates of MG were between 75.60% and 83.24%. Therefore, the Au NRs/4-MBA/PAM substrate can accurately detect and quantify veterinary drug residue in complex matrices such as food tissue. Full article

Preeclampsia (PE) is a serious complication that poses risks to both mothers and their children. This condition is typically asymptomatic until the second or even third trimester, which can lead to poor outcomes and can be costly. Detection is particularly challenging in low- and middle-income countries, where a lack of centralized testing facilities coincides with high rates of PE-related maternal mortality. Variations in the levels of hsa-miR-17-5p have been identified as constituting a potential early indicator for distinguishing between individuals with PE and those without PE during the first trimester. Thus, developing a screening test to measure hsa-miR-17-5p levels would not only facilitate rapid detection in the early stages of pregnancy but also help democratize testing globally. Here, we present a proof-of-principle lateral-flow assay (LFA) designed to measure hsa-miR-17-5p levels using DNA-hairpin recognition elements for enhanced specificity and nanoprobes for sensitive surface-enhanced resonance Raman scattering (SERS) signal transduction. The theoretical limit of detection for hsa-miR-17-5p was 3.84 × 10⁻⁴ pg/µL using SERS. Full article

Subtilisin-like proteins are serine proteases that use two types of catalytic triads: Ser-His-Asp and Ser-Glu-Asp. Here, we investigate the two known families of subtilisin-like proteins, the subtilases (Ser-His-Asp triad) and the serine-carboxyl proteinases (Ser-Glu-Asp triad), and describe the local structural arrangements (cores) that govern the catalytic residues in these proteins. We show the separation of the cores into conserved structural zones, which can be repeatedly found in different structures, and compare the structural cores in subtilisin-like proteins with those in trypsin-like serine proteases and alpha/beta-hydrolases. Full article

Two-dimensional (2D) transition metal dichalcogenides (TMDs) have recently become attractive candidate substrates for surface-enhanced Raman spectroscopy (SERS) owing to their atomically flat surfaces and adjustable electronic properties. Herein, large-scale 2D 1T′- and 2H-MoTe₂ films were prepared using a chemical vapor deposition method. We found that phase structure plays an important role in the enhancement of the SERS performances of MoTe₂ films. 1T′-MoTe₂ films showed a strong SERS effect with a detection limit of 1 × 10⁻⁹ M for the R6G molecule, which is one order of magnitude lower than that of 2H-MoTe₂ films. We demonstrated that the SERS sensitivity of MoTe₂ films is derived from the efficient photoinduced charge transfer process between MoTe₂ and adsorbed molecules. Moreover, a prohibited fish drug could be detected by using 1T′-MoTe₂ films as SERS substrates. Our study paves the way to the development and application of high-performance SERS substrates based on TMD phase engineering. Full article

The dynamic interplay between a multimeric phosphoprotein (P) and polymeric nucleoprotein (N) in complex with the viral RNA is at the heart of the functioning of the RNA-synthesizing machine of negative-sense RNA viruses of the order Mononegavirales. P multimerization and N phosphorylation are often cited as key factors in regulating these interactions, but a detailed understanding of the molecular mechanisms is not yet available. Working with recombinant rabies virus (RABV) N and P proteins and using mainly surface plasmon resonance, we measured the binding interactions of full-length P dimers and of two monomeric fragments of either circular or linear N-RNA complexes, and we analyzed the equilibrium binding isotherms using different models. We found that RABV P binds with nanomolar affinity to both circular and linear N-RNA complexes and that the dimerization of P protein enhances the binding affinity by 15–30-fold as compared to the monomeric fragments, but less than expected for a bivalent ligand, in which the binding domains are connected by a flexible linker. We also showed that the phosphorylation of N at Ser389 creates high-affinity sites on the polymeric N-RNA complex that enhance the binding affinity of P by a factor of about 360. Full article

Radiotherapy combined with a radiosensitizer represents an important treatment for head and neck squamous cell carcinoma (HNSCC). Only a few chemotherapy agents are currently approved as radiosensitizers for targeted therapy. Oral squamous cell carcinoma is one of the deadliest cancers, with approximately ~500,000 new diagnosed cases and 145,000 deaths worldwide per year. The incidence of new cases continues to increase in developing countries. This study aimed to investigate the effect of Croton tonkinensis and Curcuma longa on cell viability in OSCC cells. The HNSCC cell line OML1 and its radiation-resistant clone OML1-R were used. The anticancer effect and the mechanism of action of Croton tonkinensis and Curcuma longa in OSCC cells were analyzed by using cell viability assays, Western blot analysis, and Tranwell migration assays. The results showed that Croton tonkinensis concentration-dependently reduced the viability of OML1 and OML1-R (radioresistant) cells by downregulating the levels of AKT/mTOR mediators, such as p110α, p85, pAKT (ser473), p-mTOR (ser2448), and p-S6 Ribosomal (ser235/236). We found that cotreatment of OML1 and OML1R cells with either zVAD-FMK (apoptosis inhibitor), Ferrostatin-1 (Fer-1, a ferroptosis inhibitor), or chloroquine (CQ, an autophagy inhibitor) markedly reduced cell death. These results demonstrate that Croton tonkinensis exhibits anti-proliferation activity and highlight the therapeutic potential of small-molecule inhibitors against PI3K/mTOR signaling for radiosensitization in HNC treatment. Full article

Pancreatic lipase is an enzyme crucial for breaking down fats through hydrolysis, and inhibiting it is important for managing obesity. This study evaluated the lipase inhibitory profile of the leaf (SALE) and vine (SAVE) of Secamone afzelii, explored the modes of inhibition, identified the primary compounds responsible for this effect, and examined their molecular interactions with lipase using in vitro and in silico techniques. SALE (IC50: 0.41 ± 0.02 mg/mL) exhibited higher lipase inhibitory activity compared to SAVE (IC50: 0.95 ± 0.05 mg/mL), although it was significantly lower than orlistat (IC50: 0.07 ± 0.00 mg/mL) across all concentrations. S. afzelii extracts inhibited lipase activity through an uncompetitive mode of inhibition. Gas chromatography-mas spectroscopy identified 54 and 47 compounds in SALE and SAVE, respectively, with 9,12-octadecadienoic acid (Z, Z)-, n-hexadecanoic acid and 4S,6R-dimethyl-7R-hydroxynonan-3-one identified as the most abundant compounds in both extracts. The binding energy of the top five ligands from S. afzelii ranged from −7.7 to −6.6 kcal/mol, outperforming that of orlistat (−4.4 kcal/mol). The ligands and orlistat had similar binding poses stabilised by hydrogen and π interactions with CYS299, SER301, CYS304, ASN425 and VAL426. These compounds were predicted to possess promising pharmacokinetic, lipophilic and hydrophilic properties. These results offer insights into the traditional use of S. afzelii for treating obesity and valuable information on potential drug candidates that can be optimised for combating this disease. Full article

The objective was to evaluate the effects of potassium fertilization on the morphogenetic, structural, and productive characteristics of Panicum maximum (cvs. Tanzania, Quênia, Mombaça, Zuri, Massai, and Tamani). The design was in randomized blocks with four doses of potassium (K) 0, 205, 410, and 820 mg dm⁻³, divided into 5 applications. The analyzed variables were leaf appearance rate (LAR), leaf elongation rate (LER), stem elongation rate (SER), leaf senescence rate (LSR), leaf life span (LLS), phyllochron (PC), number of live leaves (NLL), final leaf length (FLL), tiller population density (TPD), and forage mass (FM). LAR increased by 0.00216 leaves tiller on day-1 (p = 0.0354) and LER increased by 0.00980 cm tiller on day-1 for each milligram of K (p = 0.0402). There was an increase in FLL of 0.16, 0.08, and 0.07 days for the cultivars Mombaça, Massai, and Tamani, respectively, for each milligram of K applied (p = 0.0034). The TPD of the cultivar Tamani increased linearly by 0.074 tillers/pot for each milligram of K (p = 0.0226), and the cultivar Massai showed a quadratic behavior. The TPD of the other cultivars was not influenced by the increase in the K doses. For forage mass (FM), the cultivars Mombaça and Quênia increased by 0.16 and 0.39 g DM/pot for each milligram of K added to the soil. The cultivars Tanzânia, Zuri, Massai, and Tamani showed maximum point at doses of 261.35, 279.45, 300.57, and 275.86 mg dm⁻³ K, respectively. Potassium fertilization linearly increased leaf appearance and elongation, with maximum productivity reached at a K dose of 430 mg dm⁻³, except for the cultivars Mombaça and Quênia, which responded up to a K dose of 820 mg dm⁻³. Full article

Automatic Speech Emotion Recognition (SER) plays a vital role in making human–computer interactions more natural and effective. A significant challenge in SER development is the limited availability of diverse emotional speech datasets, which hinders the application of advanced deep learning models. Transfer learning is a machine learning technique that helps address this issue by utilizing knowledge from pre-trained models to improve performance on a new task in a target domain, even with limited data. This study investigates the use of transfer learning from various pre-trained networks, including speaker embedding models such as d-vector, x-vector, and r-vector, and image classification models like AlexNet, GoogLeNet, SqueezeNet, ResNet-18, and ResNet-50. We also propose enhanced versions of the x-vector and r-vector models incorporating Multi-Head Attention Pooling and Angular Margin Softmax, alongside other architectural improvements. Additionally, reverberation from the Room Impulse Response datasets was added to the speech utterances to diversify and augment the available data. Notably, the enhanced r-vector model achieved classification accuracies of 74.05% Unweighted Accuracy (UA) and 73.68% Weighted Accuracy (WA) on the IEMOCAP dataset, and 80.25% UA and 79.81% WA on the CREMA-D dataset, outperforming the existing state-of-the-art methods. This study shows that using cross-domain transfer learning is beneficial for low-resource emotion recognition. The enhanced models developed in other domains (for non-emotional tasks) can further improve the accuracy of SER. Full article

Cooperative MIMO communication systems play an important role in the development of future sixth-generation (6G) wireless systems incorporating new technologies such as massive MIMO relay systems, dual-polarized antenna arrays, millimeter-wave communications, and, more recently, communications assisted using intelligent reflecting surfaces (IRSs), and unmanned aerial vehicles (UAVs). In a companion paper, we provided an overview of cooperative communication systems from a tensor modeling perspective. The objective of the present paper is to provide a comprehensive tutorial on semi-blind receivers for MIMO one-way two-hop relay systems, allowing the joint estimation of transmitted symbols and individual communication channels with only a few pilot symbols. After a reminder of some tensor prerequisites, we present an overview of tensor models, with a detailed, unified, and original description of two classes of tensor decomposition frequently used in the design of relay systems, namely nested CPD/PARAFAC and nested Tucker decomposition (TD). Some new variants of nested models are introduced. Uniqueness and identifiability conditions, depending on the algorithm used to estimate the parameters of these models, are established. Two families of algorithms are presented: iterative algorithms based on alternating least squares (ALS) and closed-form solutions using Khatri–Rao and Kronecker factorization methods, which consist of SVD-based rank-one matrix or tensor approximations. In a second part of the paper, the overview of cooperative communication systems is completed before presenting several two-hop relay systems using different codings and configurations in terms of relaying protocol (AF/DF) and channel modeling. The aim of this presentation is firstly to show how these choices lead to different nested tensor models for the signals received at destination. Then, by capitalizing on these models and their correspondence with the generic models studied in the first part, we derive semi-blind receivers to jointly estimate the transmitted symbols and the individual communication channels for each relay system considered. In a third part, extensive Monte Carlo simulation results are presented to compare the performance of relay systems and associated semi-blind receivers in terms of the symbol error rate (SER) and channel estimate normalized mean-square error (NMSE). Their computation time is also compared. Finally, some perspectives are drawn for future research work. Full article

Food safety has recently become a widespread concern among consumers. Surface-enhanced Raman scattering (SERS) is a rapidly developing novel spectroscopic analysis technique with high sensitivity, an ability to provide molecular fingerprint spectra, and resistance to photobleaching, offering broad application prospects in rapid trace detection. With the interdisciplinary development of nanomaterials and biotechnology, the detection performance of SERS biosensors has improved significantly. This review describes the advantages of nanomaterial-based SERS detection technology and SERS’s latest applications in the detection of biological and chemical contaminants, the identification of foodborne pathogens, the authentication and quality control of food, and the safety assessment of food packaging materials. Finally, the challenges and prospects of constructing and applying nanomaterial-based SERS sensing platforms in the field of food safety detection are discussed with the aim of early detection and ultimate control of foodborne diseases. Full article