Luminescence最新文献

Trimethylamine oxide (TMAO), a microbial metabolite commonly found in foods, has been attracting increasing attention as it is associated with the risk of several diseases. Simple and accurate analytical methods are crucial for TMAO study. In the present study, we proposed a chemical reaction-based fluorescence assay for TMAO detection using synthetic small molecular probes. After systematic screening and optimization, the sensitive and selective quantification of TMAO has been achieved based on a fluorescence probe P6 (3-iodopropanyl group modified resorufin). Excellent linearity (R² = 0.997) was found between 6.25 and 50 μM, and the limit of detection (LOD) was 0.20 μM. Using this method, TMAO levels in several marine fishes and shellfishes have been successfully analyzed. The probe-based assay offers a simple and useful way for TMAO determination. The design is inspired by the unique oxidation reaction between TMAO and halogen, which opens a new perspective in the development of more advanced analytical assays for TMAO in the future.

The synthetic strategy for the benzothiazole–benzonitrile chromophore 6 involved three sequences of reactions. It was initiated by condensation of 2-amino-4-nitrothiophenol (2) with 4-(piperidin-1-yl)benzaldehyde (1) to produce the corresponding 5-nitrobenzothiazole compound 3 followed by reduction of compound 3 into the 5-aminobenzothiazole compound 4 and then ended by condensation of 5-aminobenzothiazole compound 4 with 4-formylbenzonitrile (5). The chromophore's absorption and emission spectra have been measured in EtOH and presented good Stokes' shift ($��∆�\overline{\nu }�$ = 8363 cm⁻¹). The DFT configuration of the frontier molecular orbits in gas and solvated ground state (S_o) were compared with the solvated excited state (S₁). The synthesized chromophore 6 was assessed for its antimicrobic properties against a group of bacterial and fungal strains. The minimum inhibitory concentration (MIC) values were determined using standard broth microdilution assay. Notably, chromophore 6 exhibited remarkable MIC values against Staphylococcus aureus and Escherichia coli (< 48 and < 118 μg/mL). Regarding the antibacterial effectiveness against both S. aureus and E. coli, molecular docking was performed to simulate their binding interactions with two protein structures, PDB:2eg7 and PDB:3u2k. The SwissADME study has been applied to explore the pharmacokinetic and pharmacodynamic characteristics of chromophore 6.

Glutathione-protected silver nanoclusters (GSH-AgNCs) with good photostability were successfully synthesized through a one-pot heating process. The resultant GSH-AgNCs with an average diameter of ~1.6 nm exhibit red fluorescence (λ_em = 650 nm), and the fluorescence is excitation independent. Strong aggregation-induced emission (AIE) effect was observed in GSH-AgNCs, which can be induced by solvent and metal ions. In particular, a specific fluorescence enhancement was detected upon interaction with lead ions (Pb²⁺). A fluorescent probe was designed for off–on detection of Pb²⁺ based on as-synthesized GSH-AgNCs. Under the optimum parameters, two linear response intervals were found between the relative fluorescence intensity and the concentration of Pb²⁺ in the range of 10–250 μM (R² = 0.9900) and 400–1000 μM (R² = 0.9930). Significant fluorescence color evolutions observed under UV light, resulting in a semiquantitative visual detection of Pb²⁺. A possible detection mechanism based on the interaction between GSH-AgNCs and Pb²⁺ is discussed.

In this work, a simple, low-cost method for fabricating random gain media from Rhodamine B dye solution containing highly-pure CuO nanoparticles in transparent resin hosts is proposed. The spectroscopic characteristics of the dye solution samples were investigated with varying dye concentrations, along with nanoparticles of different particle sizes and concentrations. The fabricated samples were excited using two laser sources (405 and 530 nm) to record the fluorescence spectra. Our findings indicate that nanoparticles ranging in size from 15 to 78 nm may not have a significant impact on the fluorescence intensity or the peak wavelength at which maximum fluorescence occurs. Additionally, the fluorescence peak width, centered around 595 nm showed minimal sensitivity to the variation in particle size. The optimal concentration of nanoparticles in the dye solution was determined based on the optimum values of scattering spectral width and anisotropy parameter. Subsequently, the gain coefficient was calculated and correlated with these two parameters. It was found that the samples with the highest fluorescence intensity can be achieved using dye dissolved in transparent resin at a molar concentration of 5 × 10⁻⁵ M, containing 0.03–0.04 mg of CuO nanoparticles with a particle size of 78 nm.

Embarking on a journey to decipher the role of active sites in the detection and removal of toxic mercury(II) ions from polluted water, the surface of thermally engineered biomass derived carbon matrix NC-180 was customized with nitrogen atoms. The HR-TEM and XRD analyses revealed the amorphous nature of Lantana camara derived carbon material with small spherical flakes embedded in it. XPS analysis indicated the presence of pyrrolic, pyridinic, and graphitic N atoms, which was further confirmed by FT-IR analysis. The material shows quenching effect in presence of Hg²⁺ ions resulting in the “turn off” effect with a detection limit of 7.2 nM. The activity of NC-180 was recovered through “turn on” effect in the presence of L-cysteine. Furthermore, the mystery of binding of mercury(II) ions with N-sites is clarified through its comparison with other materials bearing sulfur and oxygen functional groups designated as AC-180, SC-180, and NSC-180. The conclusive evidence for efficient binding of nitrogen sites in NC-180 with mercury(II) ions is derived from various analyses, including ¹H-NMR, FT-IR, XPS, and density functional theory. Notably, sustainability is achieved through utilization of toxic weed L. camara for the preparation of this selective carbon material for detection and adsorption of mercury(II) ions.

This study aims to investigate the action mechanism of guaijaverin on pancreatic lipase from multiple perspectives and provide a theoretical basis for the search for new pancreatic lipase inhibitors. The inhibition of pancreatic lipase by guaijaverin was investigated through enzyme inhibition activity experiments, and the IC₅₀ was calculated to determine the type of inhibition of guaijaverin. The mechanism of action was studied by measuring fluorescence, ultraviolet spectra, and circular dichroism. Molecular docking technology was used to explore the binding situation. In addition, in vivo oral lipid tolerance tests in rats were carried out to investigate the inhibitory effect of guaijaverin on pancreatic lipase. Guaijaverin inhibited pancreatic lipase up to 90.63%, confirming its excellent inhibitory ability. The inhibition type was noncompetitive inhibition in reversible inhibition. The multispectral experiments indicated that its quenching type was static quenching and guaijaverin changed the microenvironment and spatial conformation of pancreatic lipase. The molecular docking results showed that the minimum binding energy between the two compounds was −6.96 kcal/mol. In vivo experiments demonstrated that guaijaverin inhibits pancreatic lipase by reducing TG uptake in the body. Guaijaverin has excellent inhibitory effects on pancreatic lipase and has the potential to function as a pancreatic lipase inhibitor.

Crowding environment has a significant impact on the folding and stability of protein in biological systems. In this work, we have used four different sizes of a molecular crowder, polyethylene glycol (PEG), to analyze the unfolding and refolding kinetics of an iLBP protein, CRABP I, using urea as chemical denaturant. In general, the stability of the native state of the protein is boosted by the presence of crowding agents in the solution. However, our findings show that not only the type of crowder but also the crowder size played a key role in the effects of excluded volume. In case of lower molecular weight of PEG (M.W. 400), even at 200 g/L concentration, only the viscosity effect is observed, whereas for higher molecular weight of PEG (M.W. 1000), both the viscosity effect and excluded volume effect are noticed, and even at a higher concentration (200 g/L) of PEG 1000, the excluded volume predominates over the viscosity effect. Using the transition state theory, we were also able to determine the free energies of activation for the unfolding and refolding studies from their respective rate constants. Additionally, MD simulation studies provide strong support for our experimental observation. Analysis of secondary structure propensity (SSP) reveals a marked decline in the presence of structural elements (β-sheet, β-bridge, turn, and α-helix) from 81% to 43% over the 1 μs time scale unfolding MD simulation under 8 M urea conditions. Conversely, in a 200 ns refolding simulation, the rate of refolding notably increases at a concentration of 200 g/L PEG 1000.

In this study, we employ spectroscopic, thermodynamic and molecular docking approaches to identify the mechanism by which thiazolidinone derivatives 4a–4d bind with human serum albumin. It has been suggested that the affinity of the interaction of derivatives 4a–4d with HSA is within the optimal range necessary for the transportation and distribution of compounds within the organism. The binding constant values for the derivative/HSA complexes were found to be 0.03–5.87 × 10⁵ M⁻¹. Both ΔH⁰ and ΔS⁰ values were negative, which indicates that binding occurs mainly through van der Waals forces and hydrogen bonding. The negative values calculated for ΔG⁰ indicate that the binding of derivatives 4a–4d with HSA is a spontaneous process. Our study also reveals that derivatives 4a–4d bind to the subdomain IB (Site III) of HSA and that this binding alters the conformation and thermodynamic stability of HSA. Molecular docking simulations suggest that the main binding forces are van der Waals interactions, hydrophobic interactions and hydrogen bonds. The studied compounds showed weak DPPH-scavenging activity at all of the tested concentrations. The results suggest that compound 4b with a phenyl substituent at the nitrogen atom of the 1,3-thiazolidin-4-one moiety can be considered the most potent antioxidant in the series.

Spherical-shaped nickel cobaltite (NC) nanoparticles were synthesized via a simple sol–gel technique and calcined at 600°C. X-ray diffraction (XRD) analysis revealed significant changes in crystallite size, with an average of 23 nm for the control sample and variations observed after 50 shockwaves. Fourier transform infrared spectroscopy (FTIR) confirmed metal-oxygen stretching, indicating structural integrity. UV–visible absorption studies showed changes in the optical band gap, which increased after shock treatments, suggesting bandgap tunability for optoelectronic and photovoltaic applications. The material exhibited good optical absorption up to 600 nm, making it suitable for light-harvesting devices. Vibrating sample magnetometry (VSM) detected shifts in dipole moments and magnetic saturation, with all samples displaying paramagnetic behavior. The shock-treated samples showed enhanced magnetic properties, which could be useful in magnetic storage devices. The combined tunability of bandgap and magnetic properties via shock wave treatment underscores the potential of these nanoparticles for applications in photovoltaics, spintronics, and energy storage systems.