Synchronous Fluorescence Spectra Research Articles

Cold Pressed Oil from Japanese Quince Seeds (Chaenomeles japonica): Characterization Using DSC, Spectroscopic, and Monolayer Data

The cold-pressed oil from Japanese quince seeds (JQSO) is notable for its favorable fatty acid profile, low oxidation rate, and bioactive compounds like antioxidants, sterols, and carotenoids. This study offers a detailed molecular-level physical characterization of JQSO and its minor components using differential scanning calorimetry (DSC), Langmuir monolayer studies, and various spectroscopic methods, including UV–vis absorption, fluorescence, and FTIR. DSC analysis identified five peaks related to triglyceride (TG) fractions and provided insights into the melting and crystallization behavior of JQSO. The Langmuir monolayer studies revealed high compressibility, indicative of superior emulsification properties. Viscoelastic modulus measurements suggested strong intermolecular interactions, contributing to the oil’s resilience under stress—an attribute typical of oils high in saturated or monounsaturated fatty acids. Spectroscopic methods confirmed the presence of phenolic acids, tocopherols, carotenoids, and their derivatives. The total fluorescence spectra highlighted prominent peaks at 290 nm/330 nm and 360 nm/440 nm, while the total synchronous fluorescence spectra revealed key excitation–emission regions (10–50 nm/300 nm and 40–140 nm/360 nm), corroborating the presence of tocopherols, phenols, polyphenols, flavones, and carotenoids. No evidence of chlorophyll was detected. The ATR-FTIR spectra validated the presence of fatty acids and triacylglycerols, emphasizing a high degree of esterification and the dominance of unsaturated fatty acids in oil structures. The methods used provided the opportunity to perform a label-free, fast, and reliable determination of the properties of JQSO. The findings confirmed that crude, cold-pressed JQSO retains its valuable bioactive components, aligning with previous research on its chemical and physical properties.

Probing the potential mechanism of permethrin exposure on Alzheimer's disease through enantiomer-specific network toxicology, multi-spectroscopic, and docking approaches

Latest observations indicated that exposure of organic environmental neurotoxins may increase the potential risk of Alzheimer's diseases (AD). As a suspected food-derived risk factor, permethrin, composed of cis-isomer and trans-isomer, is widely used as a broad-spectrum pyrethroid insecticide in agricultural crops for the arthropod pests controlling. Thus, evaluating the impact of permethrin exposure is of great importance to human health. In this study, we performed the toxicological network approach to decipher AD-related mechanisms of cis-permethrin and trans-permethrin. Based on the toxicological network construction and central network topological analysis, human serum albumin (HSA) was selected as the core targets in AD-related developing. From the analysis of the steady state and time-resolved fluorescence quenching of HSA in presence of permethrin mixture, it has been inferred that the nature of the quenching mainly originates from the dynamic modes. Experimentally, the thermodynamic parameters revealed hydrophobic interactions and van der Waals forces played a major role during quenching process. Tryptophan synchronous fluorescence spectra were blue shifted whereas the position of tyrosine synchronous spectra was red shifted during the complex formation. Three-dimensional fluorescence together with FT-IR experiment confirmed that permethrin caused the secondary structure changes in HSA. To better understand the binding patterns between HSA and cis/trans -permethrin, theoretical calculation and molecular docking were implemented. According to the electrostatic potential map, the electrophilic attack region corresponds for electron rich oxygen atoms, while the nucleophilic attack regions were mainly located at over the benzene rings and methyl on cyclopropane ring of permethrins. Docking results shown that cis-permethrin and trans-permethrin located in hydrophobic pocket nearby Domain IIA with the different binding affinity (−7.6 and −9.2 kcal/mol), which consistent with the competitive displacement experiment. All these findings generated in the present study facilitated the elucidation of the molecular mechanism details between permethrin mixture and HSA, which provided fresh insights into the links between environmental exposure and AD-related adverse health outcomes.

Investigation on the interaction mechanism of trilobatin with pepsin and trypsin by multi-spectroscopic and molecular docking methods

Pepsin and trypsin are noteworthy for the digestion of proteins in the human body. Trilobatin is a dihydrochalone that has anti-obesity, antioxidant, and anti-diabetes functions. The interaction of trilobatin and pepsin or trypsin is not currently being explored. Therefore, in this research multiple methods involving fluorescence spectroscopy, synchronous fluorescence spectroscopy, ultraviolet–visible (UV–Vis) spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, circular dichroism (CD) and molecular docking were employed for studying the interaction between trilobatin and pepsin or trypsin. During the interaction between trilobatin and pepsin or trypsin, the quenching type was static quenching and a single binding site existed. The binding constants (Ka) values were 2.177 and 3.028 × 104 L/mol in trilobatin-pepsin and trilobatin-trypsin system at 298 K, respectively. However, the presense of metal ions (Zn2+, Ca2+ and K+) decreased the binding of trilobatin to pepsin and trypsin. The complex between trilobatin and pepsin was generated typically through hydrogen bonding and van der Waals force (ΔH° < 0 and ΔS° < 0), in comparison the complex between trilobatin and trypsin was established chiefly through hydrogen bond and hydrophobic force (ΔH° > 0 and ΔS° > 0). The data from UV–Vis, synchronous fluorescence, FT-IR and CD spectra indicated that trilobatin reduced the hydrophobicity of Tyrosine (Tyr) residues of pepsin and trypsin. Furthermore, trilobatin altered the secondary structures of pepsin and trypsin. Meanwhile, trilobatin changed the conformation of pepsin and trypsin so that the viscosity of the interaction systems decreased with increased of trilobatin concentration. The molecular docking modeling identified that the trilobatin interacted with amino acid residues around pepsin and trypsin. This work consistently showed the interaction between trilobatin and pepsin or trypsin, in addition to offering valuable information for the application of trilobatin.

Assessment of the binding mechanism of ergothioneine to human serum albumin: Multi-spectroscopy, molecular docking and molecular dynamic simulation

Ergothioneine (EGT) has attracted great attention due to its extremely potent antioxidant properties, universally acknowledged as ‘longevity vitamin’. In order to comprehensive understanding of its pharmacodynamics and pharmacokinetics, the binding mechanism of EGT with human serum albumin (HSA) was clarified by cutting-edged multi-spectroscopic approaches and in silico molecular docking coupled with molecular dynamic simulation. Our fluorescence quenching results revealed that the binding of EGT to HSA was in a static quenching mode validated by the descending Stern–Volmer constant (Ksv) values (2.82, 2.36, 1.48 × 104 L mol−1) and biomolecular quenching rate constant (Kq) values (2.82, 2.36, 1.48 × 1012 L mol−1) at 298 K, 305 K, and 310 K, respectively. van’t Hoff criterion revealed the combination of EGT with HSA was a spontaneous exothermic process (ΔG = −24.16 kJ mol−1) via hydrogen bonding and van der Waals force interactions (ΔH = −60.25 kJ mol−1, ΔS = −129.44 J mol−1 K−1) at 310 K. The analysis of UV–vis absorption spectrum, synchronous fluorescence spectrum, three-dimensional fluorescence spectrum and circular dichroism indicated the addition of EGT affected the microenvironment of Trp214 and rearranged the structure of HSA. The binding replacement assay interpreted their binding site was near the subdomain IIA of HSA (Sudlow’s site I), which was intuitively exhibited by molecular docking. In addition of obvious van der Wall forces, attractive charge and Pi-alkyl interactions, the chiral betaine group (N+(CH3+)3) in the side chain of EGT was inclined to form hydrogen bonds with Lys199, Ser287 and Arg257 in the hydrophobic cavity of albumin. Moreover, the dynamic simulation reinforced the equilibrium and stability of formed docking complex by four indicators (RMSD, RMSF, Rg, SASA) within 100 ns.

Antibacterial Efficacy of Tryptophan Coordinated Silver Nanoparticles Against E. coli: Spectroscopic and Microscopic Evaluation of Bacterial Cell Death.

The capability of conventional fluorescence spectroscopy and right-angled synchronous fluorescence spectroscopy (SFS) was evaluated to quantify the antibacterial potential of chemically synthesized Tryptophan coordinated silver nanoparticles (Ag-TrpNPs). Silver nanoparticles have gained significant importance as a material of interest due to their diverse assemblies in the nanoscale range and their potent antibacterial activity. But due to toxicity of silver nanoparticles there is a dire need to coordinate these materials with some biocompatible and biodegradable molecules. The study has been focused on chemical synthesis of functional fluorescence nanomaterials based on Tryptophan molecules coordinated with silver nanoparticles (Ag-TrpNPs). The antibacterial activity of Ag-TrpNPs was assessed in bacteria due to their functional characteristics such as tuneability, biocompatibility, and bioavailability. We employed optical characterization techniques such as Ultraviolet-visible spectroscopy, dynamic light scattering (DLS), scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), fluorescence spectroscopy, and confocal microscopy to ensure the particles formation in aqueous suspension. DLS analysis confirmed the hydrodynamic size of the nanoparticles of approximately 100nm. SEM images revealed the spherical morphology and size distribution of the Ag-TrpNPs. Escherichia coli bacterial strains were used to assess the antibacterial efficacy of the Ag-TrpNPs using fluorescence spectroscopy and imaging. Initially, the agar well plate method was employed to evaluate the antimicrobial activity of the Ag-TrpNPs. The significant zones of inhibition of size 37mm at 500µg/mL and 27mm at 15.5µg/mL were reported which indicated the efficiency of Ag-TrpNPs from higher to lower concentration. Conventional and synchronous fluorescence spectra provided evidence of bacterial cell death in aqueous suspensions to ensure the interaction of Ag-TrpNPs with E. coli bacteria at different times and concentrations. SEM was employed to investigate the interaction mechanism between Ag-TrpNPs and bacterial cells. The images revealed cell wall disintegration, leading to the leakage of cellular contents, and eventually cell death occurred.

Rapid and simultaneous determination of ultratrace pefloxacin and fleroxacin residues in wastewater by Al3+ sensitized first derivative synchronous fluorescence spectrometry

In this study, a new first derivative synchronous fluorescence spectrometry (SFS) for the accurate and sensitive determination of pefloxacin (PFX) and fleroxacin (FLX) in wastewater was established. PFX and FLX were complexed with Al3+ to significantly enhance their fluorescence intensity. Because the conventional fluorescence spectra of PFX-Al3+ and FLX-Al3+ overlap significantly, the wavelength difference (Δλ = 155 nm) was chosen for SFS scanning to narrow spectral band. And the narrowed synchronous fluorescence spectra was subjected to first derivative processing. Finally, the zero intersections of the first derivative synchronous fluorescence spectra at 281.6 nm and 273.6 nm were chosen for the determination of PFX and FLX, cleverly used of spectral parameters to eliminate the serious interference between PFX-Al3+ and FLX-Al3+ and the interference of wastewater background. The limits of detection of PFX and FLX were 0.0086 ng·mL−1 and 0.0068 ng·mL−1 with linear ranges from 0.1–40 ng·mL−1 and 0.2–80 ng·mL−1, respectively. Recoveries of PFX and FLX in wastewater were 88.60 %–98.60 % and 90.00 %–95.60 %. The first derivative SFS established in this study used spectral separation instead of chromatographic separation, so that sample pretreatment was simple and the detection speed was fast. Compared the conventional method of HPLC, the test results of above two methods were close. And the new method had been successfully used for the determination of PFX and FLX residues in wastewater with good results. Therefore, the new first derivative SFS was expected to become a routine detection technology for PFX and FLX residues in wastewater and widely used.

Continuous Wavelet Transform as a Signal Processing Technique for Spectrofluorimetric Analysis of Rosuvastatin and Losartan: Greenness and Blueness Assessment.

In this study, the application of continuous wavelet transform as a signal processing technique for the spectrofluorimetric determination of rosuvastatin and losartan is investigated. Both rosuvastatin and losartan exhibited native spectrofluorometric signals with severe overlapping peaks, making their simultaneous determination challenging. To address this issue, rbio 2.4 wavelet transformation was employed to obtain zero-crossing points in the synchronous fluorescence spectra of losartan and rosuvastatin at 346 and 408 nm, respectively, making their quantification possible. The developed method was validated according to the ICH guidelines and displayed high accuracy, precision, and specificity. The method exhibited excellent linearity over concentration ranges 0.2-2.0 and 0.25-2.0 μg/mL for losartan and rosuvastatin, respectively. In addition, LOD and LOQ were 0.046 and 0.140 μg/mL for losartan and 0.036 and 0.110 μg/mL for rosuvastatin, respectively, indicating the high sensitivity of the developed method. Moreover, greenness and blueness assessments were carried, revealing a high AGREE score of 0.71 and BAGI score of 77.5 for the developed method, making it a promising greener alternative for the reported chromatographic methods. Finally, the developed method was applied to the determination of rosuvastatin and losartan in pharmaceutical formulations, posing it as a powerful greener alternative in quality control laboratories.

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.

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.

Synchronous Fluorescence Spectroscopy as a Green Method for the Prediction of Antioxidant Activity in Wine Brandy and Sweet Wine

The official method for the determination of antioxidant activity in beverages is 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay, which requires toxic reagents, is laborious, and produces waste. The aim of this work was to develop a more eco‑friendly method for the prediction of antioxidant activity in wine brandy and sweet wine using synchronous fluorescence spectra (SFS). In scanning of bulk and diluted samples, the excitation wavelength was varied from 250 to 500 nm and the wavelength interval was ranged from 20 to 100 nm. Partial least squares (PLS) regression was done on individual SFS, on unfolded SFS and on variables selected by the variable importance in the projection (VIP) algorithm, while the DPPH assay was the reference method. VIP-PLS modeling of the SFS of diluted samples led to better performance characteristics of the regression models. The best VIP-PLS model for wine brandy with relative predictive deviation (RPD) of 3.9 was based on 62 variables (the wavelength interval from 80 to 100 nm and the excitation wavelength from 290 to 320 nm). The best VIP-PLS model for sweet wine with RPD of 4.2 was calculated on 108 variables (the wavelength interval from 60 to 100 nm and the excitation wavelength from 260 to 290 nm). RPD values above 3.5 indicated very good prediction accuracy obtained by VIP-PLS models. Analytical GREEnness (AGREE) score 0.74 confirmed a high level of greenness of the proposed method.

Eco-friendly second derivative synchronous fluorescence spectroscopic method for simultaneous determination of rosuvastatin and ezetimibe in pharmaceutical capsules

The fixed dose combination of Rosuvastatin and ezetimibe has recently received approval from the FDA for the treatment of elevated levels of low-density lipoprotein cholesterol in adults. Herein, an eco-friendly and highly sensitive spectrofluorimetric method was developed and validated for simultaneous determination of rosuvastatin and ezetimibe in commercial capsules. The developed method involved synchronous fluorescence spectroscopy combined with second derivative spectroscopy to resolve the overlapping fluorescence spectra of rosuvastatin and ezetimibe. The studied drugs were measured in synchronous mode at Δλ of 40 and their recorded synchronous fluorescence spectra were derivatized into second-order spectra, enabling the selective quantification of rosuvastatin and ezetimibe at 370 nm and 312 nm, respectively. Optimization studies regarding to the influence of buffer pH, incorporation of surfactant, choice of diluting solvent, and synchronous Δλ were carried out. The method was validated using the validation characteristics listed in ICH Q2(R1). The calibration curves displayed satisfactory linear relationships across the calibration range of 0.1–2 µg/mL for rosuvastatin and 0.05–3 µg/mL for ezetimibe. The methodology demonstrated robustness to minor modifications in the procedural parameters and selectivity in quantifying the studied drugs in synthetic mixed solutions and commercial capsules without interference. Furthermore, the level of environmental friendliness and sustainability of the suggested spectrofluorimetric approach was assessed in relation to two previously documented methodologies utilizing the AGREE metric. The findings indicated that the suggested method demonstrated a notably superior level of sustainability in comparison to the documented methods.

Differentiating Nylon Samples with Visually Indistinguishable Fluorescence Using Principal Component Analysis and Common Dimension Partial Least Squares Linear Discriminant Analysis with Synchronous Fluorescence Spectroscopy.

Fluorescence spectroscopy is an attractive candidate for analyzing samples of nylon. Impurities within the polymers formed during the synthesis and processing of nylons give rise to the observed fluorescence, allowing for nylons to be analyzed based on their impurities. Nylons from the same source are expected to display similar fluorescence profiles, and nylons with different fluorescence are expected to be from different sources. This paper investigates an important case where different nylons displayed similar fluorescence, preventing easy discrimination. Samples of Nylon 6 and Nylon 6/12 had visually indistinguishable excitation-emission matrices (EEM), excitation spectra, fluorescence spectra, and synchronous fluorescence spectra at larger Δλ. By collecting synchronous fluorescence spectra at smaller Δλ, additional features in the fluorescence profiles were identified that allowed for some discrimination between the two nylons. Combining the EEM and synchronous fluorescence data with chemometric algorithms provided a clearer differentiation between the two nylons. parallel factor analysis, principal component analysis, and common dimension partial least squares (ComDim-PLS) showed two distinct clusters in the data, with ComDim-PLS providing the greatest distinction between the clusters. The loadings revealed the variables of interest to the ComDim-PLS were the 400 nm and 335 nm bands for all synchronous fluorescence spectra, the 460 nm and 310 nm bands for the Δλ = 20 nm and Δλ = 30 nm synchronous fluorescence spectra, and the 440 nm band for the Δλ = 20 nm synchronous fluorescence spectra. The linear discriminant analysis performed with the PLS data yielded a classification accuracy of 95% with the EEM data and 100% with the synchronous fluorescence data, displaying the power of this technique to differentiate two different nylons with visually indistinguishable fluorescence spectra.

Impact of ambient conditions on the minor nutrients content in spirulina “Arthrospira platensis” (AP) extracted from Lake Chad revealed by fluorescence spectroscopy coupled with chemometric methods

In this study, the technique of fluorescence spectroscopy coupled with chemometric methods is used to analyse samples of Lake Chad Spirulina “Arthrospira platensis” (AP), either harvested and conditioned by using the traditional method at different seasons or industrially processed. The content of minor fluorescent nutrients is investigated. To this end, fluorescence excitation-emission matrices (EEMs) of 46 AP samples are recorded in aqueous solution. Synchronous fluorescence (SF) spectra are extracted from these EEMs and their important features are compared to those of PARAFAC methods. Synchronous fluorescence scanning allows different AP samples to be characterized in a single scan. The SF and PARAFAC methods yielded two groups of fluorescent compounds; the first group, consisting of vitamin-like molecules, shows excitation/emission (ex/em) peaks at 340/460, 390/462, 370/440 and 450/526 nm, attributed to caffeic acid, vitamin K, E and riboflavins respectively, while the second group, consisting of pigments, shows ex/em peaks at 610/654, 590/630 and 570/644 nm, attributed to phycocyanins, C-phycocyanin and allophycocyanin. Our fluorescence data showed that while both vitamins and pigments are present in AP during the rainy season, only fluorescent components of vitamin-like compounds are present during the dry season. PCA methods allowed classifying different AP samples according to their geographic origin and harvesting season. Fluorescence spectroscopy therefore appears to be a powerful technique for rapidly assessing the chemical composition of AP.

Association mechanism of bicalutamide and human serum albumin for potential clinical implications.

The binding mechanism of molecular interaction between bicalutamide and human serum albumin (HSA) in a pH7.4 phosphate buffer was studied using various spectroscopic techniques in combination with molecular modeling. Fluorescence data revealed that the fluorescence quenching of HSA by bicalutamide was a static quenching procedure. The binding constants and number of binding sites were evaluated at different temperatures. The thermodynamic parameters, ΔH and ΔS, were calculated to be 4.30 × 104J·mol-1 and 245 J·mol-1·K-1, respectively, suggesting that the binding of bicalutamide to HSA was driven mainly by hydrophobic interactions and hydrogen bonds. The displacement studies indicated neither Sudlow's site I nor II but subdomain IB as the main binding site for bicalutamide on HSA. The binding distance between bicalutamide and HSA was determined to be 3.54 nm based on the Förster theory. Analysis of circular dichroism, synchronous, and 3D fluorescence spectra demonstrated that HSA conformation was slightly altered in the presence of bicalutamide.

The interaction between resveratrol and catalase was studied by multispectral method and molecular docking simulation

In this research, we delved into the interaction mechanism between Resveratrol (RES) and Catalase (CAT) utilizing a suite of advanced analytical techniques, including multispectral analysis and molecular docking simulation. A comprehensive assessment of their binding characteristics, modalities, distances, and the subsequent impact on CAT's secondary structure was conducted through fluorescence spectroscopy, ultraviolet spectroscopy, circular dichroism, three-dimensional fluorescence spectroscopy, synchronous fluorescence spectroscopy, and molecular docking simulation. By employing the Stern-Volmer equation to determine KSV and Kq values, Our findings indicate that the RES-CAT interaction results in static fluorescence quenching, By conducting experiments, the binding constant KA and the number of binding sites n for CAT and RES were determined, with the number of binding sites n being close to 1, indicating the presence of a specific binding site between CAT and RES. Parameters at 298 K. The negative values of ΔH and ΔS suggest that van der Waals forces and hydrogen bonding are predominant in mediating the interaction between CAT and RES. The negativity of ΔG indicates the spontaneity of the reaction. The Fӧrster resonance energy transfer theory calculation revealed a binding distance of 4.917 nm, substantiating the occurrence of non-radiative energy transfer between RES and CAT. Furthermore, the UV-VIS absorption spectrum, synchronous fluorescence spectrum, three-dimensional fluorescence spectrum, and circular dichroism analyses collectively demonstrated that RES induces alterations in CAT's secondary structure, augmenting the polarity around tryptophan (Trp) residues, reducing hydrophobic interactions, and bolstering hydrophilicity. This work offers novel insights into the antioxidant mechanisms of resveratrol within biological systems and holds significant theoretical and practical implications for the medical application and development of resveratrol.

Sensitive detection of pymetrozine residues based on β-lactoglobulin as a fluorescence probe

A method was developed for the detection of pymetrozine (PYM) using β-lactoglobulin (β-LG) as a probe. The interaction between PYM and β-LG was studied by fluorescence spectra, circular dichroism spectra (CD), synchronous fluorescence spectra, ultraviolet visible spectra (UV–vis), fourier transform infrared (FT-IR) and molecular docking. The fluorescence quenching type between PYM and β-LG was demonstrated to be static by Stern-Volmer analysis and time-resolved fluorescence. The binding constant (Ka) was 2.95 × 104 L mol−1 at 293 K. The electrostatic attraction was confirmed to be the primary binding force by Ross theory, and the binding distance was 2.02 nm by fluorescence Resonance Energy Transfer (FRET) theory. Based on the interaction between β-LG and PYM, a fluorescence detection method for PYM was established. Under optimal experimental conditions, the standard equations were established in the range of 0.43 – 10.68 μg mL−1. The limit of detection (LOD) for PYM was 0.03 μg mL−1. The method was successfully applied to apple and pear fruit samples. Recoveries of PYM in these samples were 97.44 % – 102.29 %, the relative standard deviation (RSD) of these samples were 0.24 % – 0.88 % (n = 3).

Probing the interaction between the metallo-β-lactamase SMB-1 and ampicillin by multispectral approaches combined with molecular dynamics.

Metallo-β-lactamases (MβLs) hydrolyze and inactivate β-lactam antibiotics, are a pivotal mechanism conferring resistance against bacterial infections. SMB-1, a novel B3 subclass of MβLs from Serratia marcescens could deactivate almost all β-lactam antibiotics including ampicillin (AMP), which has posed a serious threat to public health. To illuminate the mechanism of recognition and interaction between SMB-1 and AMP, various fluorescence spectroscopy techniques and molecular dynamics simulation were employed. The results of quenching spectroscopy unraveled that AMP could make SMB-1 fluorescence quenching that mechanism was the static quenching; the synchronous and three-dimensional fluorescence spectra validated that the microenvironment and conformation of SMB-1 were altered after interaction with AMP. The molecular dynamics results demonstrated that the whole AMP enters the binding pocket of SMB-1, even though with a relatively bulky R1 side chain. Loop1 and loop2 in SMB-1 undergo significant fluctuations, and α2 (71-73) and local α5 (186-188) were turned into random coils, promoting zinc ion exposure consistent with circular dichroism spectroscopy results. The binding between them was driven by a combination of enthalpy and entropy changes, which was dominated by electrostatic force in agreement with the fluorescence observations. The present study brings structural insights and solid foundations for the design of new substrates for β-lactamases and the development of effective antibiotics that are resistant to superbugs.

Interaction mechanism of oseltamivir phosphate with bovine serum albumin: multispectroscopic and molecular docking study

Oseltamivir phosphate (OP) is an antiviral drug with potential risks to human health due to overuse, leading to serious consequences such as gastrointestinal disturbances, abnormal neuropsychiatric symptoms, and sudden death. Therefore, gaining an in-depth understanding of its interaction with proteins is crucial. We investigated the interaction between OP and bovine serum albumin (BSA) utilizing multispectral methods (i.e., fluorescence, ultraviolet absorption, circular dichroism) combined with molecular docking techniques. Fluorescence spectroscopy indicated that OP quenched BSA fluorescence by forming the OP-BSA complex. The Stern-Volmer constants (KSV) between OP and BSA were determined to be 3.06 × 103 L/mol, 2.36 × 103 L/mol, and 1.86 × 103 L/mol at 293 K, 298 K, and 303 K, respectively. OP occupies exclusively one binding site on BSA, and the fluorescent probe displacement measurements revealed that this is BSA site I. Thermodynamic data (∆H, ∆S, and ∆G) obtained by fitting the van’t Hoff equation were − 77.49 kJ/mol, -176.54 J/(mol∙K), and − 24.88 kJ/mol, respectively, suggesting that hydrogen bonding and van der Waals forces mainly participate in OP-BSA complex stabilization. Moreover, the reaction occurs spontaneously at room temperature. Synchronous fluorescence spectra indicated that OP interacts with tryptophan residue of BSA. The results of ultraviolet (UV) and 3D fluorescence spectroscopy indicated that the OP-BSA complex formation altered the microenvironment around amino acid residues. Circular dichroism spectra revealed that the addition of OP decreased the α-helix content of BSA by 7.13%. Docking analysis confirmed that OP binds to BSA site I through hydrogen bonding with amino acids VAL342, SER453, and ASP450. Finally, ADMET studies were conducted to explore the pharmacokinetics of OP as an antiviral drug.

Green micellar factorial design optimized first derivative synchronous spectrofluorimetric method for tripelennamine and diphenhydramine determination in pharmaceutical gel.

A green micellar synchronous spectrofluorimetric method was developed and validated for simultaneous determination of tripelennamine hydrochloride and diphenhydramine in bulk and combined pharmaceutical formulation. Synchronous fluorescence of tripelennamine hydrochloride and diphenhydramine was determined using Δλ = 60 nm. The first derivative of synchronous fluorescence was computed to resolve overlap in the synchronous fluorescence spectra. Tripelennamine hydrochloride was quantified at 375 nm, whereas diphenhydramine was quantified at 293 nm; each is the zero-crossing point of the other. As diphenhydramine exhibited weak native fluorescence, micelle enhancement upon incorporation of sodium dodecyl sulfate was considered. Two-level full factorial design was carried out to optimize experimental parameters. Optimum conditions involved using SDS (2% w/v) along with Teorell and Stenhagen buffer (pH9). The method was found to be linear over the range 0.2-4.5 and 0.2-5μg/mL for tripelennamine and diphenhydramine, respectively, with limits of detection 0.211 and 0.159 μg/mL. The method was successfully applied for simultaneous determination of tripelennamine hydrochloride and diphenhydramine in laboratory-prepared gel containing all possible excipients with mean percent recoveries ±SD 100.59 ±0.79 and 98.99 ±0.98 for tripelennamine hydrochloride and diphenhydramine, respectively. The proposed method was proved to be eco-friendly using different greenness assessment tools.

Synthesis and Characterizations of MoS2 Nanoflowers and Spectroscopic Study of their Interaction with Bovine Serum Albumin.

Molybdenum disulfide nanoflowers (MoS2 NFs) were prepared by hydrothermal method. The prepared MoS2 NFs was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), specific surface areas, Raman and X-ray photoelectron spectroscopy (XPS). The characterization results show that the flower-like spherical MoS2 is composed of many ultra-thin nanosheets with an average diameter of about 300-400 nm. MoS2 NFs also exhibits excellent UV-vis absorption and high fluorescence intensity. In order to explore the biological behavior of MoS2 NFs, the interaction between MoS2 NFs and bovine serum albumin (BSA) was studied by UV-Vis absorption, fluorescence, synchronous fluorescence spectra, and cyclic voltammetry. The results of absorption and fluorescence show that MoS2 NFs and BSA interact strongly through the formation of complexes in the ground state, and the static quenching is the main mechanism. The Stern-Volmer constant and the quenching constant was calculated about 3.79×107 L mol-1 and 3.79×1015 L mol-1 s-1, respectively. The synchronous fluorescence implied that MoS2 in the complex may mainly bind to tryptophan residues of BSA. The cyclic voltammograms indicated that the addition of BSA makes electron reduction of MoS2 NFs more difficult than the corresponding free state. The results show that hydrophobic forces play a major role in the binding interaction between BSA and MoS2 NFs.