Fluorescence Spectra Research Articles

Low-moisture extruded mung bean protein isolate and wheat gluten: Structure, techno-functional characteristics and establishment of rehydration kinetics of the products

Low-moisture extruded products provide excellent shelf-life and stability, making the exploration of new formulations with various proteins highly valuable. This study prepared and compared products with different ratios of mung bean protein isolate (MPI) to wheat gluten (WG) (10:0, 9:1, 8:2, 7:3, 6:4, and 5:5). Results showed significant improvements (P < 0.05) in L∗-value and product quality with increasing WG ratios, peaking at an MPI/WG ratio of 7:3. Increased WG also enhanced protein cross-linking aggregation, as evidenced by changes in particle size, secondary structure, and fluorescence spectra. However, excessive WG (MPI/WG = 6:4) adversely affected product structure and techno-functional characteristics. Rehydration kinetics were best described by the Peleg model, with rehydrated products showing decreased hardness (291.25 N) and chewiness (227.45 N), but increased tensile resistance (P < 0.05). Eleven quadratic polynomial equations were developed to predict color and techno-functional characteristics based on WG percentage (0–50%). The findings provide a theoretical basis for expanding the application of MPI in new low-moisture extruded products.

Carbohydrate-Binding Mechanism of the Coagulant Lectin from Moringa oleifera Seeds (cMoL) Is Related to the Dimeric Protein Structure

This study characterized the binding mechanisms of the lectin cMoL (from Moringa oleifera seeds) to carbohydrates using spectroscopy and molecular dynamics (MD). The interaction with carbohydrates was studied by evaluating lectin fluorescence emission after titration with glucose or galactose (2.0–11 mM). The Stern–Volmer constant (Ksv), binding constant (Ka), Gibbs free energy (∆G), and Hill coefficient were calculated. After the urea-induced denaturation of cMoL, evaluations were performed using fluorescence spectroscopy, circular dichroism (CD), and hemagglutinating activity (HA) evaluations. The MD simulations were performed using the Amber 20 package. The decrease in Ksv revealed that cMoL interacts with carbohydrates via a static mechanism. The cMoL bound carbohydrates spontaneously (ΔG &lt; 0) and presented a Ka on the order of 102, with high selectivity for glucose. Protein–ligand complexes were stabilized by hydrogen bonds and hydrophobic interactions. The Hill parameter (h~2) indicated that the binding occurs through the cMoL dimer. The loss of HA at urea concentrations at which the fluorescence and CD spectra indicated protein monomerization confirmed these results. The MD simulations revealed that glucose bound to the large cavity formed between the monomers. In conclusion, the biotechnological application of cMoL lectin requires specific methods or media to improve its dimeric protein structure.

The relationship between chlorophyll fluorescence and polarized light field: Polarization-Curve Fluorescence Height

The impact of the un-polarized nature of chlorophyll fluorescence, which causes a dip in the degree of polarization of the underwater light field matching the fluorescence spectrum, led to the development of a theoretical relationship indicating that the resulting fractional reduction in observed polarization is linearly proportional to the magnitude of the fluorescence causing it. To evaluate this relationship, we used a vector radiative transfer code (VRTE) for the coupled atmosphere-ocean system using measured inherent optical properties (IOPs) for a variety of oligotrophic and eutrophic waters as inputs. The VRTE was used to simulate elastic components of the underwater reflectance as well as the degree of linear polarization (DoLP) for these different conditions. These values were compared with the underwater reflectances and the DoLPs measured by a multi-angular hyperspectral polarimeter to determine the magnitude of the fluorescence component in the reflectance spectra at 685 nm, and the decrease of the DoLP due to the fluorescence impact at the same wavelength. Fluorescence magnitudes retrieved from the differences between simulated and measured reflectances were found to match well the magnitudes estimated through the relationship based on the drop of the DoLP. It is noted that retrieval accuracies increase for both larger fluorescence and larger underlying DoLP values. Furthermore, a new method is evolved from the measured polarization analysis, Polarization-Curve Fluorescence Height (PCFH). Measured polarization were used to approximate the elastic signal and derive the inelastic un-polarized signal (fluorescence) from the difference in the fluorescence vicinity. These results open possibilities for estimating the magnitude of natural fluorescence using polarization measurements below or above the water surface, .in-situ, or remotely from aircraft or future satellites. Results of ongoing work on potential sensitivities and retrieval accuracies for these applications will be reported.

Probing amikacin interaction with albumin: A combined multispectral and molecular docking investigation

The fate of a drug administered to a living organism depends on the pharmacological and pharmacokinetic behavior of drugs. Biological macromolecules like serum albumins have a crucial role in the design and biological safety assessments of drugs. Amikacin as an example of the most used semi-synthetic aminoglycosides antibiotics, is included in the crucial drug list of the World Health Organization. This in vitro study aimed to explore Amikacin's binding specification with bovine serum albumin (BSA) through a computational and experimental approach. According to fluorescence spectra, it was declared that the innate fluorescence emission of serum albumin was quenched by the Amikacin via a static quenching mechanism. Meantime, the binding constants and thermodynamic parameters of Amikacin with BSA were calculated at various temperatures. Based on this calculation, negative ΔG°, ΔH°, and ΔS° values showed that spontaneous binding process occurred via hydrogen bond and van der Waals interaction. Additionally, based on UV–vis absorption, Amikacin leads to conformational modifications of BSA with the construction of a ground state complex, which may affect the physiological functions of this serum albumin. The results of FTIR spectroscopy showed that the binding of amikacin led in the change of BSA secondary structure and confirmed the possibility of changing the physiological functions of BSA. It is anticipated that this research will supply significant insight into the pharmacological properties of Amikacin and its related effects on human health in vivo.

Theoretical Investigation on Proton Transfer Directionality and Dynamics Behavior of 3-(Benzo[d]thiazol-2-yl)-2-hydroxy-5-methoxybenzaldehyde with Two Asymmetric Proton Acceptors.

A detailed theoretical investigation on the excited state intramolecular proton transfer (ESIPT) directionality and dynamics behavior of 3-(benzo[d]thiazol-2-yl)-2-hydroxy-5-methoxybenzaldehyde (BTHMB) with two unsymmetric proton acceptors (N and O2) has been performed. The hydrogen bond O1-H···N in BTHMB-a formed by the O1-H group with the N atom or O1-H···O2 in BTHMB-b formed by the O1-H group with the O2 atom is enhanced upon photoexcitation, and the strength of the O1-H···N bond is stronger, which will drive the O1-H proton to the N atom. Potential energy curves further confirm that ESIPT occurs in the N atom because of the smaller energy barrier (0.39 kcal/mol). Results of dynamics simulations manifest that no surface hopping exists between the S0 and S1 states within 300 fs, and ESIPT time constants of BTHMB-a and BTHMB-b are 48 and 151 fs, respectively. While the reverse ESIPT is observed in BTHMB-b at 294 fs, implying that the O1-H proton is transferred to the N atom instead of the O2 atom. The consistency of the calculated absorption (390 nm) and fluorescence spectra (443 and 602 nm) of BTHMB-a with the experimental values (390, 410, and 605 nm) confirms this conclusion again. The charge distribution analysis shows that the charge on the proton acceptors increases, and the O2 atom has higher electronegativity because it has more negative charges. The minimum surface electrostatic potential on the N atom in BTHMB-b correlating with the pKb value is -47.38 kcal/mol, indicating that the N atom has strong basicity. Therefore, the basicity of the N atom dominates the ESIPT process rather than the electronegativity of the O2 atom.

Insight into the mechanism of alkali-thermal pretreatment of food-waste solid residue through fluorescence spectroscopy coupled with parallel factor analysis

Food-waste solid residue is the remaining solid after food waste treatment, with high yield, high solid content, high protein and fiber content. Effective pretreatment is necessary to improve the efficiency of hydrolysis and acidification for anaerobic digestion of food-waste solid residue. In this study, fluorescence spectroscopy coupled with parallel factor analysis were used to insight into the mechanism of food-waste solid residue during three pretreatments (alkali, thermal and alkali-thermal). Pretreatments increased the solubility of lignocellulosic substrate and destroyed structure of starch, while lignocellulosic analogs were effectively cracked, changing the composition and improving the degradability. Soluble chemical oxygen demand, soluble protein and soluble polysaccharide concentrations were increased by 144.60%, 350.57% and 138.72% after pretreatment under the condition of 120 °C + 2% CaO, respectively. Three-dimensional fluorescence spectra showed the region of maximum fluorescence intensity under alkali-thermal pretreatments, indicating chemical bonds (such as OC–C) were easier broken and the solubility of organic substances were increased. Three main fluorescence components were obtained by parallel factor analysis, which were humic acid-like, lignocellulose-like and protein-like, respectively, while the lignocellulose-like had the maximum Fmax value. The fluorescence intensity of samples under alkali-thermal pretreatment varied in the range from 59.48 × 105 to 13.18 × 106, which was an increase of 174.27%–507.74% over the control (21.68 × 105), indicating that alkali-thermal pretreatment observably accelerated the breaking of chemical bonds, and thus promoted the dissolution of organic matter. This study deeply revealed the mechanism of alkali-thermal pretreatment of food-waste solid residue, which is of great significance for efficient resource utilization of food waste and food-waste solid residue.

An environmentally sustainable synchronous spectrofluorimetric method coupled with second derivative signal processing for simultaneous determination of velpatasvir and simeprevir in pharmaceutical and plasma samples

Velpatasvir and simeprevir are two direct acting antivirals that are often used in combination with sofosbuvir to treat HCV infections. Herein, an environmentally benign spectrofluorimetric method was developed for simultaneous quantification of velpatasvir and simeprevir in pharmaceutical and plasma samples. To address the issue of overlapping fluorescence spectra presented by these compounds, this method integrates synchronous fluorescence and second-derivative spectroscopy. By employing the second derivative of the synchronous fluorescence spectra measured at Δλ of 140 nm, the accurate determination of velpatasvir at 400 nm and simeprevir at 426 nm was achieved without any interference. Different experimental parameters affecting the synchronous fluorescence of the studied drugs were carefully optimized. The plots of second-derivative amplitudes against concentrations showed linearity in the range of 5–400 ng/mL for velpatasvir and 80–800 ng/mL for simeprevir. The method was very sensitive, with lower detection limits of 1.11 ng/mL and 25.40 ng/mL, and quantification limits of 3.36 ng/mL and 76.96 ng/mL for velpatasvir and simeprevir, respectively.The method was effectively used to determine velpatasvir and simeprevir simultaneously in their pure forms, pharmaceutical dosage forms, and human plasma with no interference. The suggested technique was additionally evaluated for its eco-friendliness through the utilization of the Analytical GREEnness (AGREE) and Green Analytical Procedure Index (GAPI) evaluation metrics, revealing that the method is indeed sustainable.

Construction of Carbon Dioxide Responsive Graphene Point Imbibition and Drainage Fluid and Simulation of Imbibition Experiments

The global oil and gas exploration targets are gradually moving towards a new field of oil and gas accumulation with nanopore throats, ranging from millimeter scale to micro-nano pore throats. The development method of tight oil reservoirs is different from that of conventional oil reservoirs, and the development efficiency is constrained. Therefore, it is necessary to construct a nanoscale fluid with strong diffusion and dispersion and improve its permeability, suction, and displacement capabilities. Under the background of CCUS, carbon dioxide flooding is a better way to develop tight reservoirs. However, in order to solve the problem of gas channeling, this paper developed a carbon dioxide-responsive graphene point type surfactant, which has a good gas–liquid synergistic effect. At the same time, graphene nanomaterials are carbon-based and create no environmental damage in oil reservoirs. In this study, graphene quantum dots (GQDs) were prepared using the hydrothermal method, and functional graphene quantum dots (F-GQDs) responsive to carbon dioxide stimulation were synthesized by covalent grafting of amidine functional groups. By characterizing its structure and physical and chemical properties, and by conducting imbibition simulation experiments, its imbibition and drainage ability in nanopore throats is elucidated. Infrared spectrum measurement shows that after functional modification, the quantum dots exhibited new characteristic peaks at 1600 cm−1 to 1300 cm−1, considering the N-H plane-stretching characteristic peak. The fluorescence spectra showed that the fluorescence intensity of F-GQDs was increased after functional modification, which indicated that F-GQDs were successfully synthesized. Through measurements of interfacial activity and adhesion work calculations, the oil–water interfacial tension can achieve ultra-low values within the range of 10−2 to 10−3 mN/m. Oil sand cleaning experiments and indoor simulations of spontaneous imbibition in tight cores demonstrate that F-GQDs exhibit effective oil-washing capabilities and a strong response to carbon dioxide. When combined with carbon dioxide, the system enhances both the rate and efficiency of oil washing. Imbibition recovery can reach more than 50%. The research results provide a certain theoretical basis and data reference for the efficient development of tight reservoirs.

Synthesis and optical applications of Yb3+/Er3+ co-doped Ba0.6Bi0.4F2.4 and its heterostructured Ca0.6Bi0.4F2.4 upconversion luminescent materials

Bismuth-based composite fluoride upconversion luminescent materials exhibit uniform size and excellent upconversion properties. These materials have potential applications in photodynamic therapy, anti-counterfeiting technology, and bio-imaging. Thus, bismuth-based composite fluoride luminescent materials have been the subject of extensive study in recent years. This paper focuses on the design and synthesis of bismuth-based composite fluorides, specifically Yb3+/Er3+ co-doped Ba0.6Bi0.4F2.4 and its heterostructured Ca0.6Bi0.4F2.4 upconversion luminescent materials. The study involves measuring room temperature fluorescence spectra, fluorescence lifetime, and quantum yield, demonstrating the exceptional luminescence performance of Ca0.6Bi0.4F2.4:Yb3+/Er3+. More importantly, we successfully obtained transparent lanthanide-doped Ca0.6Bi0.4F2.4 thermoplastic polyurethane (TPU) luminescent films and upconversion luminescent inks. This work highlights the great potential of upconversion nanomaterials in anti-counterfeiting fields.

Design and Synthesis of Aggregation‐Caused Quenching Hydroxy‐Phenanthroimidazole Derivatives for Probing of Fe3+ ions and as Potential Blue Light Emitters

Fluorescence aggregated molecules tend to employ versatile opportunities in metal ion probe sensors and fluorescent lighting. To achieve this dual challenging task, currently synthesized three phenanthroimidazole‐naphthalene‐based compounds Pq‐tBu‐OH, Pq‐mF‐OH, and Pq‐pF‐OH are derived based on substitution at N1 position for better photophysical and electrochemical properties. Compared experimental and theoretical calculations define the highest bandgap to be 2.75 eV of Pq‐pF‐OH, and the same molecule expressed a higher (348 °C) thermal decomposition. The calculated singlet and triplet energies found in the range of 3.24‐3.67 and 2.70‐2.72 eV indicates well energy transfer from S1®S0 (quantum yield of 23.36%, lifetime is 4.05 ns). Among the numerous morphologies, the solid form exhibited improved intensive deep blue emission (x=0.159, y=0.051), and its InGaN LED results demonstrated a strong deep blue emission at 418 nm. Moreover, the fluorophores were experimentally visualizing the aggregation‐caused quenching (ACQ) which enables the probing of Fe3+ ion. However, for the first time, the ACQ‐assisted concept is applied through synthesized molecules for Fe3+ ion probing via fluorescence spectra, Job’s plot calculation, and 1H NMR results. In addition, the probe works excellently at a detection limit of 10 µM and it could also act as a potential competitor for lighting applications.

Enhanced functionalization of superparamagnetic Fe3O4 nanoparticles for advanced drug enrichment and separation applications

Backgroundsuperparamagnetic ferroferric oxide (Fe3O4) nanoparticles can be extensively functionalized for applications in drug enrichment and separation. Their high magnetic responsiveness and controllable surface modification enable rapid drug enrichment and separation under external magnetic fields. This study aimed to enhance the application potential of superparamagnetic Fe3O4 nanoparticles in the field of drug enrichment and separation by functionalizing these nanoparticles to improve their biocompatibility and targeting capabilities.Methodssuperparamagnetic Fe3O4 nanoparticles functionalized with dopamine were synthesized using benzyl alcohol as the solvent and iron acetylacetonate as the precursor. The dopamine-functionalized superparamagnetic iron oxide nanoparticles were used to analyze protein enrichment and separation. Characterization of the nanoparticles was conducted, including analysis of particle size distribution, Zeta potential, and fluorescence spectra using a fluorescence spectrophotometer.Resultsthe Fe3O4 nanoparticles maintained high magnetism from the original material and exhibited uniform particle size distribution and stable Zeta potential. The saturation magnetization of dopamine-functionalized superparamagnetic Fe3O4 nanoparticles showed no significant difference compared to before coating, indicating minimal influence of dopamine on the internal magnetic core of the nanoparticles. The Fe3O4 nanoparticles demonstrated good biocompatibility and stability.Conclusionfunctionalization of superparamagnetic Fe3O4 nanoparticles significantly enhances their efficiency in drug enrichment and separation processes, suggesting broad applications in the pharmaceutical industry.

Mitochondria-Targeted Ratiometric KLA-Tweezers for Fluorescence Imaging of Potassium Ions.

Intracellular potassium ions play a crucial role in cellular homeostasis associated with physiological and pathological processes. It is still challenging but definitely crucial to precisely and dynamically image subcellular K+. Herein, the first mitochondria-targeted DNA tweezers (KLA-tweezers) were developed for the fluorescence imaging of mitochondrial K+ with high selectivity and accuracy. The proposed KLA-tweezers consisted of two DNA double-crossover (DX) motifs, a K+-aptamer, and a mitochondria-targeted peptide (KLA) which was conjugated at the rear of DX arms via complementary base pairing. Upon contact with K+, the K+-aptamer experienced a conformational change from an open-chain G-rich sequence to a G-quadruplex with a compact conformation, which was reflected by the Förster resonance energy transfer process between Cy3 and Cy5 labeled at the end of the DX arms. The open and closed states of the tweezers before and after KLA modification were confirmed by gel electrophoresis and fluorescence spectra together with atomic force microscopy (AFM) and transmission electron microscopy (TEM) images, suggesting the KLA assembly had no effect on the morphology change. The proposed tweezers and KLA-tweezers showed low cytotoxicity, excellent selectivity, and good reversibility upon alternating addition of 18-crown-6 and K+. Besides, the KLA-tweezers exhibited outstanding stability and accurate mitochondria location ability. Upon stimulation of ATP or nigericin, intracellular fluorescence imaging of mitochondrial K+ dynamics was successfully achieved. This strategy has broad prospects as a general optical sensing platform for other metal ions or organelles in living cells.

Multi-color emission composites of white carbon dots and dyes through inner filter effect

A series of multi-color carbon dot composites were obtained by transforming white carbon dots (WCDs) into three primary colors using the dyes' inner filter effect (IFE). WCDs were combined with three distinct dyes (methyl red, bromocresol green, and methylene blue), and three fluorescence colors (red, yellow, and blue) were obtained. The colors of the emitting light excited by the same UV light were similar to the colors of the respective dyes, and have a large Stokes shift. The presence of the IFE between WCDs and dyes was proved through a variety of methods, the analysis of the relationship between the UV of dyes and fluorescence spectra of WCDs, the excitation-emission matrix, as well as the comparison PL decay profiles of WCDs before and after dye addition. The Stern-Volmer quenching constant KSV exhibited no temperature dependence during the IFE process with increasing concentrations of dyes. The UV spectra of the mixture of WCDs and dyes were simply the sum of two individual components, which implies that there is no chemical interaction between WCDs and dyes. Since methyl red and bromocresol green are acid-base indicators, the fluorescence color of the carbon dot composite also changed continuously during the dilute NaOH solution titration process. In furtherment, distributing the binary system of “WCDs + dye” within poly (vinyl alcohol) (PVA), three colors fluorescent composite films of “WCDs / Dye / PVA” were produced successfully.

Effects of Soy Protein Isolate and Inulin Conjugate on Gel Properties and Molecular Conformation of Spanish Mackerel Myofibrillar Protein.

The gel properties and molecular conformation of Spanish mackerel myofibrillar protein (MP) induced by soy protein isolate-inulin conjugates (SPI-inulin conjugates) were investigated. The addition of SPI-inulin conjugates significantly enhanced the quality of the protein gel. An analysis of different additives was conducted to assess their impact on the gel strength, texture, water-holding capacity (WHC), water distribution, intermolecular force, dynamic rheology, Raman spectrum, fluorescence spectrum, and microstructure of MP. The results demonstrated a substantial improvement in the strength and water retention of the MP gel with the addition of the conjugate. Compared with the control group (MP), the gel strength increased from 35.18 g·cm to 41.90 g·cm, and WHC increased from 36.80% to 52.67% with the inclusion of SPI-inulin conjugates. The hydrogen bond content was notably higher than that of other groups, and hydrophobic interaction increased from 29.30% to 36.85% with the addition of SPI-inulin conjugates. Furthermore, the addition of the conjugate altered the secondary structure of the myofibrillar gel, with a decrease in α-helix content from 62.91% to 48.42% and an increase in β-sheet content from 13.40% to 24.65%. Additionally, the SPI-inulin conjugates led to a significant reduction in the endogenous fluorescence intensity of MP. Atomic force microscopy (AFM) results revealed a substantial increase in the Rq value from 8.21 nm to 20.21 nm. Adding SPI and inulin in the form of conjugates is an effective method to improve the gel properties of proteins, which provides important guidance for the study of adding conjugates to surimi products. It has potential application prospects in commercial surimi products.

Adapalene as a chemical sensor for sensitive determination of manganese

ABSTRACT The work describes the use of 6-[3-(1-adamantyl)-4-methoxyphenyl]-2- naphthoic acid, or Adapalene (ADP) as a fluorescence tagging reagent, in a straightforward and very specific spectrofluorometric approach for the trace measurement of manganese (VII) in water. The process is based on the redox interaction of ADP with manganese (VII) in an acidic solution, which forms the complex [Mn (II)-ADP] and causes fluorescence at λex max/λem max = 323/400 nm. High-intensity fluorescence at 400 nm was seen in the fluorescence spectra of the formed complex ion association, Mn (II)-ADP, at pH 4. 1.55 µg mL−1 was the quantification limit, and 0.51 µg mL−1 was the detection limit and the correlation coefficient (R2) was 0.9863. 1.2173 L mol−1 was determined to be the Stern-Volmer. Spectrofluorometric technique is used to validate the approach in environmental water samples, yielding reasonable recovery percentages (89–93%). The current approach is advised to be used for reliable and accurate assessment of manganese (VII) in all wastewater and seawater samples, without the need for complex instrumentation and lengthy procedures.

Structure, J-O analysis, and near-infrared luminescence of Er3+/Yb3+ doped SiO2–B2O3-GdF3-CaO-Bi2O3 glass

SiO2–B2O3-GdF3-CaO-Bi2O3 doped glasses containing Er3+/Yb3+ ions at varying concentrations were successfully synthesized using a high-temperature melting method. The glass samples' physicochemical properties and amorphous structure were characterized through density, XRD, XPS, FT-IR, and Raman analyses. Thermal expansion coefficient testing indicated good thermal stability of the glass system. Increasing the Yb3+ doping concentration enhanced near-infrared luminescence at 1.53 μm, with maximum luminescence intensity at approximately 3.2 mol% doping concentration. The energy transfer mechanism of Er3+/Yb3+ doped SiO2–B2O3-GdF3-CaO-Bi2O3 glass was elucidated through fluorescence spectrum analysis, revealing J-O parameters Ω2 = 11.2 × 10−20 cm2, Ω4 = 8.9 × 10−20 cm2, and Ω6 = 9.59 × 10−20 cm2. Calculations for absorption cross-section, cross-section of emission, and gain curve additionally reinforced the glass's capability for laser uses.

Covalent interaction of ovalbumin with proanthocyanidins improves its thermal stability and antioxidant and emulsifying activity.

The structure of proanthocyanidins (PC) contains a large number of active phenolic hydroxyl groups, which makes it have strong antioxidant capacity. This study investigated the structural and functional properties of ovalbumin (OVA) modified by its interaction with PC. It was found that on increasing the concentration ratio of PC to OVA from 10:1 to 40:1, the free amino and total sulfhydryl contents of OVA decreased from 470.59 ± 38.77 and 29.81 ± 0.31 nmol mg-1 to 96.61 ± 4.55 and 21.22 ± 0.78 nmol mg-1, respectively, and the free sulfhydryl content increased from 7.65 ± 0.41 to 9.48 ± 0.58 nmol mg-1. These results indicated that CN and CS bonds were formed and PC was covalently linked with OVA. The PC content in the OVA-PC conjugates increased from 281.93 ± 12.92 to 828.81 ± 46.09 nmol mg-1 on increasing the concentration ratio of PC to OVA from 10:1 to 40:1. The contents of α-helix and β-turn of OVA decreased, and the contents of β-sheet and random coil increased, confirmed by circular dichroism. The tertiary structure of OVA was also altered according to the results of fluorescence and ultraviolet absorption spectra. The surface hydrophobicity of OVA-PC conjugates decreased with increasing bound polyphenol content. The conjugation of OVA to PC significantly improved its emulsification and antioxidant activity and denaturation temperature. This study may provide valuable information for improving OVA's functional properties and its PC conjugates for applications in the food industry. © 2024 Society of Chemical Industry.

Investigation on the anti-α-glucosidase mechanism of aspergillus triazolate A from Oxalis corniculate L.

Diabetes mellitus characterized by abnormal glucose concentration is a metabolic disease. α-Glu inhibitors from natural sources are a good choice for searching for high-efficiency and low-toxicity hypoglycemic drugs. In this study, a naturally effective α-Glu inhibitor aspergillus triazolate A (ATA) with a peculiar structure was first found in Oxalis corniculate L., then its activity and mechanism were first elucidated through various methods. These mechanisms included enzyme kinetics, circular dichroism spectra, fluorescence spectra, synchronous fluorescence spectrum, 3D fluorescence spectrum, and molecular docking. Meanwhile, the ability to reduce postprandial blood glucose was further investigated in vivo. Research results revealed that ATA was a mixed type α-Glu inhibitor with an IC50 value of 66.87 ± 1.50 μM, which bound to the enzyme from a single site through hydrogen bonding and hydrophobic forces causing the looser secondary structure of α-Glu. It was also found that the binding site of α-Glu was closer to the Trp residue, and the endogenous fluorescence of α-Glu was quenched in a static quenching form. Moreover, the sucrose loading test in vivo revealed that the ATA of 20 mg/kg could effectively reduce the postprandial blood glucose level. Hence, ATA could be used as lead compound to develop novel α-Glu inhibitors.

The study on characterization of interaction between casticin and model proteins using spectroscopic and computational methodologies

The present studies were conducted to investigate the interaction of casticin to model proteins (BSA, HSA, OVA and HEL) using fluorescence spectra, Fourier transform infrared spectra, molecular docking and molecular dynamics simulation methodologies. Our work displayed that the endogenous fluorescence intensities of BSA, HSA, OVA and HEL were quenched by various concentrations of casticin were the typical static quenching process. The binding constants (Ka) of casticin for these model proteins were in the range of 104–105 mol·L-1, with the highest affinity for HSA. On the basis of thermodynamic parameters and computational simulation studies, it was suggested that the binding force of casticin to BSA, HSA, OVA and HEL were mainly hydrogen bonds, van der Waals forces and hydrophobic interactions. The spectral results illustrated that the binding of casticin to BSA, HSA, OVA and HEL induced conformational and microenvironmental changes. Casticin could decrease the α-helix percentages of BSA, HSA and OVA, but increase that of HEL. Binding substitution studies confirmed that casticin bound to the Sudlow site I of BSA and HSA. Molecular docking predicted the binding models of casticin to BSA, HSA, OVA and HEL, followed closely by molecular dynamic simulations to assess the binding stability.

Analysis of spectroscopic characteristics of Sm3+ ions doped gallium silicate glasses for orange-red LEDs

In this work, a variety of Sm3+ ions doped gallium silicate glasses have been made using the conventional melt quenching procedure, and characterized by X-ray diffraction, absorption spectrum, fluorescence spectrum, fluorescence decay curves, respectively. The density of the glass increases with the increase of the concentration of Sm3+ ions, and XRD shows that the samples are all amorphous glasses. Absorption spectra were used to determine the J-O intensity parameters (Ωλ, λ = 2, 4, 6), as well as the radiation transition probability(A), fluorescence branching ratio(βr), and radiation lifetime(τr) of Sm3+ ions at the 4G5/2 energy level. Under 403 nm excitation, the emission spectra show obvious emission peaks at 602 nm and 649 nm, corresponding to 4G5/2 → 6H7/2 and 4G5/2 → 6H9/2 transitions respectively. The B3 glass sample has the largest emission cross section(σem) at the 4G5/2 → 6H7/2 transition, with σem = 11.40 × 10−22 cm2. The color coordinates, color purity and color temperature values of all samples were calculated. The color purity of all samples varied in the range of 96.20%–99.14 %, with the relevant samples separating in the orange-red light region. The experimental results indicate that the glass samples have a potential application prospect in the field of orange-red LEDs.