Fluorescence Spectroscopic Methods Research Articles

Quantitation of Tissue Amyloid via Fluorescence Spectroscopy Using Controlled Concentrations of Thioflavin-S.

Amyloids are misfolded proteins that aggregate into fibrillar structures, the accumulation of which is associated with the pathogenesis of many neurodegenerative diseases, such as Alzheimer's disease (AD). Early, sensitive detection of these misfolded aggregates is of great interest to the field, as amyloid deposition begins well before the presentation of clinical symptoms. Thioflavin-S (ThS) is a fluorescent probe commonly used to detect amyloid pathology. Protocols for ThS staining vary, but they often use high staining concentrations followed by differentiation, which causes varying levels of non-specific staining and potentially leaves more subtle amyloid deposition unidentified. In this study, we developed an optimized ThS staining protocol for the sensitive detection of β-amyloids in the widely used 5xFAD Alzheimer's mouse model. Controlled dye concentrations together with fluorescence spectroscopy and advanced analytical methods enabled not only the visualization of plaque pathology, but also the detection of subtle and widespread protein misfolding throughout the 5xFAD white matter and greater parenchyma. Together, these findings demonstrate the efficacy of a controlled ThS staining protocol and highlight the potential use of ThS for the detection of protein misfolding that precedes clinical manifestation of disease.

Polymeric Micelles Formulation of Combretastatin Derivatives with Enhanced Solubility, Cytostatic Activity and Selectivity against Cancer Cells.

Combretastatin derivatives is a promising class of antitumor agents, tubulin assembly inhibitors. However, due to poor solubility and insufficient selectivity to tumor cells, we believe, their therapeutic potential has not been fully realized yet. This paper describes polymeric micelles based on chitosan (a polycation that causes pH and thermosensitivity of micelles) and fatty acids (stearic, lipoic, oleic and mercaptoundecanoic), which were used as a carrier for a range of combretastatin derivatives and reference organic compounds, demonstrating otherwise impossible delivery to tumor cells, at the same time substantially reduced penetration into normal cells. Polymers containing sulfur atoms in hydrophobic tails form micelles with a zeta potential of about 30 mV, which increases to 40-45 mV when cytostatics are loaded. Polymers with tails of oleic and stearic acids form poorly charged micelles. The use of polymeric 400 nm micelles provides the dissolution of hydrophobic potential drug molecules. Micelles could significantly increase the selectivity of cytostatics against tumors, which has been shown using MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay, Fourier transform infrared (FTIR) spectroscopy, flow cytometry and fluorescence microscopy. Atomic force microscopy presented the difference between the unloaded micelles and those loaded with the drug: the size of the former was 30 nm on average, while the latter had a "disc-like" shape and a size of about 450 nm. The loading of drugs into the core of micelles was confirmed by UV and fluorescence spectroscopy methods; shifts of absorption and emission maxima into the long-wavelength region by tens of nm was observed. With FTIR spectroscopy, a high interaction efficiency of micelles with the drug on cells was demonstrated, but at the same time, selective absorption was observed: micellar cytostatics penetrate into A549 cancer cells 1.5-2 times better than the simple form of the drugs. Moreover, in normal HEK293T, the penetration of the drug is reduced. The proposed mechanism for reducing the accumulation of drugs in normal cells is the adsorption of micelles on the cell surface and the preservation of cytostatics to penetrate inside the cells. At the same time, in cancer cells, due to the structural features of the micelles, they penetrate inside, merging with the membrane and releasing the drug by pH- and glutathione-sensitive mechanisms. From a methodological point of view, we have proposed a powerful approach to the observation of micelles using a flow cytometer, which, in addition, allows us to quantify the cells that have absorbed/adsorbed cytostatic fluorophore and distinguish between specific and non-specific binding. Thus, we present polymeric micelles as drug delivery systems in tumors using the example of combretastatin derivatives and model fluorophore-cytostatic rhodamine 6G.

A self-organizing map approach to the analysis of lake DOM fluorescence for differentiation of organic matter sources.

The sources and properties of dissolved organic matter (DOM) in two lakes with different non-point source inputs were investigated by combining conventional three-dimensional fluorescence spectroscopy methods with a self-organizing map (SOM). To assess the DOM humification level, the representative neurons 1, 11, 25, and 36 were assessed. The SOM model showed that the DOM humification level of the Gaotang Lake (GT) which has a mainly agricultural non-point source input was significantly higher than that of the Yaogao Reservoir (YG) which has a mainly terrestrial source input (P < 0.01). The GT DOM mainly came from factors such as agricultural-related farm compost and decaying plants, while the YG DOM originated from human activities around the lake. The source characteristics of the YG DOM are obvious, with a high level of biological activity. Five representative areas in the fluorescence regional integral (FRI) were compared. The comparison showed that during the flat water period, the GT water column showed more terrestrial characteristics, even though the humus-like fractions in the DOM of both lakes were derived from microbial decomposition. Principal component analysis (PCA) showed that the agricultural lake water DOM (GT) was dominated by humus components, while the urban lake water DOM (YG) was dominated by authigenic sources.

Enhancement of Fluorescence Mediated by Silver Nanoparticles: Implications for Cell Imaging.

In this study, we report the surface enhanced fluorescence (SEF) of a biologically important organic dye, fluorescein (FL), by silver nanoparticles (Ag NPs) in an aqueous medium and its implications for human cell imaging. The as-synthesized Ag NPs were characterized by dynamic light scattering (DLS), zeta potential, transmission electron microscopy (TEM), and UV-vis absorption spectroscopic studies. The interaction and aggregation of FL dye with Ag NPs and a cationic surfactant, namely, cetyltrimethylammonium bromide (CTAB), were explored by UV-vis absorption and steady-state and time-resolved fluorescence spectroscopic methods. The distance-dependent fluorescence enhancement of FL due to Ag NPs in the solution was also theoretically correlated by three-dimensional finite-difference time-domain (3D-FDTD) simulation. The plasmonic coupling between neighboring NPs facilitated the augmentation of the local electric field, thereby producing various "hotspots" that influence the overall fluorescence of the emitter. J-type aggregates of FL in the presence of the CTAB micelles and Ag NP mixed solution were confirmed by electronic spectroscopy. The density functional theoretical (DFT) study revealed the electronic energy levels associated with different forms of FL dye in the aqueous solution. Most interestingly, the Ag NP/FL mixed system used in fluorescence imaging of human lung fibroblast cells (WI 38 cell line) showed a significantly stronger green fluorescence signal compared to that of FL after an incubation period of only 3 h. This study confirms that the Ag NP mediated SEF phenomenon of the FL dye is also manifested in the intracellular medium of human cells giving a brighter and more intense fluorescence image. The cell viability test after exposure to the Ag NP/FL mixed system was confirmed by the MTT assay method. The proposed study may have an implication as an alternate approach for human cell imaging with higher resolution and more contrast.

Aalnysis of Influencing Factors for the Detection of Total Mercury in Food by Atomic Fluorescence

With the increase of people's attention to nutrition and health, food quality and safety have also become the focus of people's daily attention, among which mercury and its compounds are widely distributed in nature, with high volatility, high toxicity and harmful accumulation. In this paper, the first method of atomic fluorescence spectroscopy in GB5009.17-2021 "National Food Safety Standard - Determination of Total Mercury and Organic Mercury in Food" was comprehensively analyzed in the detection of total mercury in food, and the key points of sample pretreatment, the on-machine detection process and the detection experiment were comprehensively analyzed. The analysis of key points of pretreatment mainly includes: sample weighing, cleaning and use of detection instruments, amount of acid in microwave digestion process, optimization and setting of microwave digestion program, and analysis and research on the elimination method of excess nitric acid after microwave digestion is completed. The analysis of the key parameters of the atomic fluorescence photometer of the detection equipment during the sample testing on the machine includes: the setting and optimization of the instrument parameters, the daily maintenance method of the key components of the instrument, etc.; Through the analysis and study of all aspects of the entire detection process, the main factors affecting the accuracy of the detection results are identified for improvement and solidification implementation, so as to more effectively improve the accuracy of the measurement results.

A novel binuclear Lanthanum complex containing 1,10-phenanthroline; from crystal structure to biological and antitumor activity

UV–Vis and IR spectroscopy, elemental analysis, and X-ray crystallography are used to characterize a novel dimeric Lanthanum(III) complex with 1,10-phenanthroline (phen), [LaCl2(Phen)2-µ-Cl2- LaCl2(Phen)2]. It is also being examined for its antibacterial, anticancer, and DNA (Fish Salmon DNA) and protein (Bovine Serum Albumin) binding properties. The title compound's crystals are triclinic, P1¯; with a (Å) = 9.914(3), b (Å) = 10.927(3), c (Å) = 12.047(3), V (Å3) = 1151.7(5), α (°) = 84.797(5), β (°) = 77.224(4), γ (°) = 64.814(5), Z = 1 and Dcalc = 1.747 (g/cm3). It has a centrosymmetric binuclear [LaCl2(Phen)2 (µ-Cl)]2 unit (the two bridging chlorine atoms lie on an inversion center). The molecular modeling method was used to study the binding qualities both empirically and conceptually. Absorption and fluorescence spectroscopy methods were used to determine thermodynamic parameters, the binding constant (Kb), and the possible binding process. With a binding constant (Kb) of 1.78 × 105, the volume of binding to FS DNA supports groove binding, which is consistent with docking estimates. With a static technique, the as-synthesized complex efficiently suppressed BSA emission and was bound by Kb = 1.17 × 105 at 298 K, demonstrating its high tendency for BSA contact via van der Waals force and hydrogen bond. Antimicrobial testing on a variety of bacteria revealed that it has good antibacterial action. The MTT method was used to test the in vitro cytotoxicity of the La2(III) complex in A-549 cell lines, which exhibited considerable activity.

Differential Behavior of Eicosapentaenoic and Docosahexaenoic Acids on the Organization, Dynamics, and Fusion of Homogeneous and Heterogeneous Membranes.

Membrane fusion is a common course in innumerable biological processes that helps in the survival of eukaryotes. Enveloped viruses utilize this process to enter the host cells. Generally, the membrane lipid compositions play an important role in membrane fusion by modulating the membrane's physical properties and the behavior of membrane proteins in the cellular milieu. In this work, we have demonstrated the role of polyunsaturated fatty acids (PUFAs), such as eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids, on the organization, dynamics, and fusion of homogeneous and heterogeneous membranes. We have exploited arrays of steady-state and time-resolved fluorescence spectroscopic methods and polyethylene glycol-induced membrane fusion assay to elucidate the behavior of EPA and DHA on dioleoyl phosphatidylcholine (DOPC)/cholesterol (CH) homogeneous and DOPC/sphingomyelin/CH heterogeneous membranes. Our results suggest that EPA and DHA display differential effects on two different membranes. The effects of PUFAs in homogeneous membranes are majorly attributed to their flexible chain dynamics, whereas the ability of PUFA-induced cholesterol transfer from the lo to the ld phase rules their behavior in heterogeneous membranes. Overall, our results provide detailed information on the effect of PUFAs on homogeneous and heterogeneous membranes.

Applications of UV-Visible, Fluorescence and Mid-Infrared Spectroscopic Methods Combined with Chemometrics for the Authentication of Apple Vinegar.

Spectroscopic techniques as untargeted methods have great potential in food authentication studies, and the evaluation of spectroscopic data with chemometric methods can provide accurate predictions of adulteration even for hard-to-identify cases such as the mixing of vinegar with adulterants having a very similar chemical nature. In this study, we aimed to compare the performances of three spectroscopic methods (fluorescence, UV-visible, mid-infrared) in the detection of acetic-acid/apple-vinegar and spirit-vinegar/apple-vinegar mixtures (1-50%). Data obtained with the three spectroscopic techniques were used in the generation of classification models with partial least square discriminant analysis (PLS-DA) and orthogonal partial least square discriminant analysis (OPLS-DA) to differentiate authentic and mixed samples. An improved classification approach was used in choosing the best models through a number of calibration and validation sets. Only the mid-infrared data provided robust and accurate classification models with a high classification rate (up to 96%), sensitivity (1) and specificity (up to 0.96) for the differentiation of the adulterated samples from authentic apple vinegars. Therefore, it was concluded that mid-infrared spectroscopy is a useful tool for the rapid authentication of apple vinegars and it is essential to test classification models with different datasets to obtain a robust model.

Controlling metal coordination geometry in dinuclear zinc and cadmium hydroxy aryl carboxylates incorporating five-membered aromatic cyclic amine co-ligands

Five dinuclear Zn and Cd carboxylate complexes, [Zn(L)(µ-L)(im)·2H2O]2 (1), [Zn(L)(µ-L)(meim).MeOH]2 (2), [Zn(L)(µ-L)(dmp)]2 (3), [Cd(L)(µ-L)(im)·2H2O]2 (4) and [Zn(L)(µ-L)(dmp)]2 (5) (HL = 3,5-diisopropyl-4-hydroxybenzoic acid, im = imidazole, meim = N- methylimidazole, dmp = 3,5-dimethylpyrazole) have been synthesized by reacting M(OAc)2·2H2O (M = Zn and Cd) with a disubstituted aromatic carboxylic acid and various five-membered aromatic cyclic amines in methanol at ambient temperature. All complexes have been characterized by elemental analysis and FT-IR, Mass, UV–Vis, fluorescence, 1H and 13C NMR spectroscopic methods. The molecular structures and bulk purity of the compounds have been established by single-crystal and powder X-ray diffraction studies. In these complexes, the carboxylate groups exhibit terminal, chelating, chelate-bridging modes of coordination. The H-atom of dmp forms an intramolecular hydrogen bond with the carboxylate-O of the nearest ligand. The structures of the binuclear products obtained in the present study have been dictated by coordination mode of the carboxylate (chelate vs brdging) and size of the metal ion (Zn vs Cd). Presence of peripheral free hydroxyl functional groups facilitate intra- and inter-hydrogen bonding in the solid state structure. The luminescent properties of 1–5 have also been studied, exhibiting ligand-centred emission around 315 nm.

Identification of Tree Species and Extent of Material Deterioration of Wood Components in the Yangjia Courtyard Ancient Building

Abstract The identification of the tree species and the extent of material deterioration in the wooden components of the walkway of the first courtyard of the ancient Yangjia Courtyard were analyzed in this study using bright-field microscopy, polarized light, fluorescence, and Fourier-transform infrared (FTIR) spectroscopy methods. The results are as follows: (1) samples No. 1 and No. 2, and No. 4, No. 3, and No. 5 taken from the roots of the wooden pillars were identified as lace-bark pine wood (Pinus bungeana), poplar woods (Populus spp.), large-fruited elm wood (Ulmus macrocarpa), and spruce wood (Picea sp.), respectively on the basis of observation of anatomical structural characteristics and analysis of selection principle of “local selection” in ancient buildings. (2) The observation of polarization and fluorescence and the analysis of FTIR spectra showed that the brightness of crystalline cellulose birefringence reduced severely, and analysis of FTIR spectra showed that the absorption peaks representing cellulose and hemicellulose in the lace-bark pine and spruce wooden components disappeared or decreased. However, the polarization and fluorescence and the FTIR spectra of the poplar and elm wooden components showed that the brightness of the crystalline cellulose birefringence and the absorption peaks remained constant, as the controls did. (3) According to the results of the effects of the polarization and fluorescence effects and the FTIR spectra, we concluded that the lace-bark pine and spruce wooden components were severely attacked by brown rot fungi; in contrast, the wooden components of poplar and elm were not attacked by wood decay fungus, but were attacked by insects. These results provide scientific guidance for subsequent preventive conservation such as preservative treatment and insect prevention.

Applications of Fluorescence Spectroscopy and Machine Learning Methods for Monitoring of Elimination of Carbon Nanoagents from the Body

Applications of Fluorescence Spectroscopy and Machine Learning Methods for Monitoring of Elimination of Carbon Nanoagents from the Body

Fluorometric Detection of Methanol by Using Triphenylamine Fluorophore Tethered Terpyridine Probe

AbstractTriphenylamine appended terpyridine donor‐acceptor fluorescent probe (TPA‐TP) exhibited specific detection of methanol in presence of other volatile organic compounds, such as benzene, ethanol and biodiesel were described. The role of the terpyridine group in the TPA‐TP toward methanol detection has been demonstrated. The detection mechanism origins from s‐trans to s‐cis and vice‐versa conformational change facilitated by hydrogen bonding interactions between TPA‐TP and methanol. Besides, TPA‐TP coated Whatman filter paper based strip was evaluated for detection of methanol from benzene prepared my means of practical and versatile applications of methanol detection. Thus, TPA‐TP was demonstrated as a sensitive, selective, and inexpensive probe for methanol detection over benzene, ethanol and biodiesel by naked‐eye and fluorescence spectroscopy methods.

Tris chelated meridional isomers of Co(III) complexes: Synthesis, crystal structure, protein binding, cytotoxicity studies and DFT/TDDFT calculation

Two mononuclear Co(III) complexes, [Co(L1)3] (1) and [Co(L2)3] (2) (HL1, 2-[(2-methoxy-ethylimino)-methyl]-phenol; HL2, 1-[(2-methoxy-ethylimino)-methyl]-naphthalen-2-ol) have been synthesized and characterized by X-ray crystal structure determination, IR and mass spectroscopic techniques. Both the complexes are mononuclear with distorted octahedral geometries and the Co(III) center are coordinated with three bidentate (O, N) Schiff base ligands. Complexes 1 and 2 form 1D and 3D supramolecular structures, respectively, with weak CH…π interactions. Experimental UV–vis absorption spectra have been compared with the results obtained from DFT / TD-DFT calculation using B3LYP functional and LanL2DZ basis set. The interaction of the complexes with bovine serum albumin (BSA) and human serum albumin (HSA) were studied using electronic absorption and fluorescence spectroscopic methods and the results show that complexes potentially quench the fluorescence of BSA/HSA through ground state association mechanism. Cytotoxicity studies of these complexes have been performed against breast cancer cell lines and found that they have moderate anticancer activity.

Low-Dimensional Compounds Containing Bioactive Ligands. Part XX: Crystal Structures, Cytotoxic, Antimicrobial Activities and DNA/BSA Binding of Oligonuclear Zinc Complexes with Halogen Derivatives of 8-Hydroxyquinoline

Two tetranuclear [Zn4Cl2(ClQ)6]·2DMF (1) and [Zn4Cl2(ClQ)6(H2O)2]·4DMF (2), as well as three dinuclear [Zn2(ClQ)3(HClQ)3]I3 (3), [Zn2(dClQ)2(H2O)6(SO4)] (4) and [Zn2(dBrQ)2(H2O)6(SO4)] (5), complexes (HClQ = 5-chloro-8-hydroxyquinoline, HdClQ = 5,7-dichloro-8-hydroxyquinoline and HdBrQ = 5,7-dibromo-8-hydroxyquinoline) were prepared as possible anticancer or antimicrobial agents and characterized by IR spectroscopy, elemental analysis and single crystal X-ray structure analysis. The stability of the complexes in solution was verified by NMR spectroscopy. Antiproliferative activity and selectivity of the prepared complexes were studied using in vitro MTT assay against the HeLa, A549, MCF-7, MDA-MB-231, HCT116 and Caco-2 cancer cell lines and on the Cos-7 non-cancerous cell line. The most sensitive to the tested complexes was Caco-2 cell line. Among the tested complexes, complex 3 showed the highest cytotoxicity against all cell lines. Unfortunately, all complexes showed only poor selectivity to normal cells, except for complex 5, which showed a certain level of selectivity. Antibacterial potential was observed for complex 5 only. Moreover, the DNA/BSA binding potential of complexes 1–3 was investigated by UV-vis and fluorescence spectroscopic methods.

Fluorescent spectroscopy paired with parallel factor analysis for quantitative monitoring of phenanthrene biodegradation and metabolite formation

Polycyclic aromatic hydrocarbons (PAHs) are a class of environmental contaminants released into the environment from both natural and anthropogenic sources that are associated with carcinogenic, mutagenic, and teratogenic health effects. Many remediation strategies for the treatment of PAH contaminated material, including bioremediation, can lead to the formation of toxic transformation products. Analytical techniques for PAHs and PAH transformation products often require extensive sample preparation including solvent extraction and concentration, chromatographic separation, and mass spectrometry to identify and quantify compounds of interest. Excitation-emission matrix (EEM) fluorescent spectroscopy paired with parallel factor analysis (PARAFAC) is an approach for analyzing PAHs that eliminates the need for extensive sample preparation and separation techniques before analysis. However, this technique has rarely been applied to monitoring PAH biotransformation and formation of PAH metabolites. The objectives of this research were to compare an established targeted analytical method to two-dimensional fluorescent spectroscopy and combined EEM-PARAFAC methods to monitor phenanthrene degradation by a bacterial pure culture, Mycobacterium Strain ELW1, identify and quantify phenanthrene transformation products, and derive kinetic constants for phenanthrene degradation and metabolite formation. Both phenanthrene and its primary transformation product, trans-9,10-dihydroxy-9,10-dihydrophenanthrene, were identified and quantified with the EEM-PARAFAC method. The value of the EEM-PARAFAC method was demonstrated in the superiority of sensitivity and accuracy of quantification to two-dimensional fluorescent spectroscopy. Quantification of targets and derivation of kinetic constants using the EEM-PARAFAC method were validated with an established gas chromatography-mass spectrometry (GC-MS) method. To the authors’ knowledge, this is the first study to use an EEM-PARAFAC method to monitor, identify, and quantify both PAH biodegradation and PAH metabolite formation by a bacterial pure culture.

Novel fluorescence spectroscopy method coupled with N-PLS-R and PLS-DA models for the quantification of cannabinoids and the classification of cannabis cultivars.

Cannabis sativa L. inflorescences are rich in secondary metabolites, particularly cannabinoids. The most common techniques for elucidating cannabinoid composition are expensive technologies, such as high-pressure liquid chromatography (HPLC). We aimed to develop and evaluate the performance of a novel fluorescence spectroscopy-based method coupled with N-way partial least squares regression (N-PLS-R) and partial least squares discriminant analysis (PLS-DA) models to replace the expensive chromatographic methods for preharvest cannabinoid quantification. Fresh medicinal cannabis inflorescences were collected and ethanol extracts were prepared. Their excitation-emission spectra were measured using fluorescence spectroscopy and their cannabinoid contents were determined by HPLC-PDA. Subsequently, N-PLS-R and PLS-DA models were applied to the excitation-emission matrices (EEMs) for cannabinoid concentration prediction and cultivar classification, respectively. The N-PLS-R model was based on a set of EEMs (n = 82) and provided good to excellent quantification of (-)-Δ9-trans-tetrahydrocannabinolic acid, cannabidiolic acid, cannabigerolic acid, cannabichromenic acid, and (-)-Δ9-trans-tetrahydrocannabinol (R2 CV and R2 pred >0.75; RPD >2.3 and RPIQ > 3.5; RMSECV/RMSEC ratio < 1.4). The PLS-DA model enabled a clear distinction between the four major classes studied (sensitivity, specificity, and accuracy of the prediction sets were all ≥0.9). The fluorescence spectral region (excitation 220-400 nm, emission 280-550 nm) harbors sufficient information for accurate prediction of cannabinoid contents and accurate classification using a relatively small data set.

Current Problems of the Diagnostics and Treatment of Sepsis and Burn Injuries: The Modified Pathogenetic Concept

Background: The deep understanding of pathogenesis is a key moment in the formation of the modern strategy of modern medicine. We conducted the thorough analysis of the microscopic processes occurring in the bodies of patients with purulent-septic complications. The modified pathogenetic concept of the diagnostic and treatment model of diseases with septic complications is presented. The obtained information about the mechanisms of origin and development of these diseases is fundamentally important for finding the modern effective methods of treating patients. The aim of the research is to modify treatment tactics for patients with sepsis and burn injuries based on the modified pathogenetic concept using modern diagnostics, i.e. the method of fluorescence spectroscopy (MFS) and biomarkers. Materials and Methods: The proposed modified pathogenetic concept of the diagnostic and treatment model of diseases with purulent-septic complications along with standard methods was used successfully for effective treatment of 15 patients with sepsis and 25 with burn injuries. Results: 3 main scenarios of behaviour of spectral-fluorescence characteristics of patients with sepsis are illustrated. Spectral-fluorescence markers of sepsis were studied, which are informative 24 to 48 hours before the appearance of obvious clinical and laboratory signs of significant changes in the general somatic status of patients. Conclusions: The proposed diagnostic and therapeutic approach is new and fundamentally important for diagnostics and monitoring of the process of treatment of patients with purulent-septic diseases and burn injuries. An in-depth understanding of the dynamics of septic complications and the corresponding changes of the main markers of these diseases during treatment is especially relevant. The use of infusion therapy with solutions of donor albumin as an effective pathogenetic treatment is scientifically justified.

Binding interactions of hydrophobically-modified flavonols with β-glucosidase: fluorescence spectroscopy and molecular modelling study.

Natural flavonoids are capable of inhibiting glucosidase activity, so they can be used for treating diabetes mellitus and hypertension. However, molecular-level details of their interactions with glucosidase enzymes remain poorly understood. This paper describes the synthesis and spectral characterization of a series of fluorescent flavonols and their interaction with the β-glucosidase enzyme. To tune flavonol-enzyme interaction modes and affinity, we introduced different polar halogen-containing groups or bulky aromatic/alkyl substituents in the peripheral 2-aryl ring of a flavonol moiety. Using fluorescence spectroscopy methods in combination with molecular docking and molecular dynamics simulations, we examined the binding affinity and identified probe binding patterns, which are critical for steric blockage of the key catalytic residues of the enzyme. Using a fluorescent assay, we demonstrated that the binding of flavonol 2e to β-glucosidase decreased its enzymatic activity up to 3.5 times. In addition, our molecular docking and all-atom molecular dynamics simulations suggest that the probe binding is driven by hydrophobic interactions with aromatic Trp and Tyr residues within the catalytic glycone binding pockets of β-glucosidase. Our study provides a new insight into structure-property relations for flavonol-protein interactions, which govern their enzyme binding, and outlines a framework for a rational design of new flavonol-based potent inhibitors for β-glucosidases.

Density effect on electronic structure of warm dense matter based on X-ray fluorescence spectroscopy

Warm dense matter (WDM), a kind of transition state of matter between cold condensed matter and high temperature plasma, is one of the main research objects of high energy density physics (HEDP). Compared with the structure of isolated atom, the electron structure of WDM will change significantly because of the influences of density and temperature effect. As WDM is always strongly coupled and partly degenerate, accurate theoretical description is very complicated and the accurate experimental research is also very challenging. In this paper, the density effect on the warm dense matter electron structure based on the X-ray fluorescence spectroscopy is studied. The warm dense titanium with density larger than solid density is produced experimentally based on a specially designed hohlraum. Then, the titanium is pumped to emit fluorescence by using the characteristic line spectrum emitted by the laser irradiating the pump material (Vanadium). The X-ray fluorescence spectra of titanium with different states are diagnosed by changing the delay time between the pump laser and drive laser. The experimental fluorescence spectrum indicates that the difference in energy between &lt;inline-formula&gt;&lt;tex-math id="M5"&gt;\begin{document}${\mathrm{K}}_{\text{β}} $\end{document}&lt;/tex-math&gt;&lt;alternatives&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="24-20231215_M5.jpg"/&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="24-20231215_M5.png"/&gt;&lt;/alternatives&gt;&lt;/inline-formula&gt; and &lt;inline-formula&gt;&lt;tex-math id="M6"&gt;\begin{document}$ {\mathrm{K}}_{\text{α}} $\end{document}&lt;/tex-math&gt;&lt;alternatives&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="24-20231215_M6.jpg"/&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="24-20231215_M6.png"/&gt;&lt;/alternatives&gt;&lt;/inline-formula&gt; (&lt;inline-formula&gt;&lt;tex-math id="M7"&gt;\begin{document}$\Delta E_{{\mathrm{K}}_{\text{β}}\text{-}{\mathrm{K}}_{\text{α}}}$\end{document}&lt;/tex-math&gt;&lt;alternatives&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="24-20231215_M7.jpg"/&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="24-20231215_M7.png"/&gt;&lt;/alternatives&gt;&lt;/inline-formula&gt;) of the compressed titanium (7.2–9.2 g/cm&lt;sup&gt;3&lt;/sup&gt;, 1.6–2.4 eV) is about 2 eV smaller than that of cold titanium. Two theoretical methods, i.e. finite-temperature relativistic density functional theory (FTRDFT) and two-step Hartree-Fock-Slater (TSHFS), are used to calculate the fluorescence spectrum of warm dense titanium. The calculated results indicate that the energy difference (&lt;inline-formula&gt;&lt;tex-math id="M10"&gt;\begin{document}$\Delta E_{{\mathrm{K}}_{\text{β}}\text{-}{\mathrm{K}}_{\text{α}}} $\end{document}&lt;/tex-math&gt;&lt;alternatives&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="24-20231215_M10.jpg"/&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="24-20231215_M10.png"/&gt;&lt;/alternatives&gt;&lt;/inline-formula&gt;) decreases with the increase of density but changes slowly with the increase of temperature during the calculated state (4.5–13.5 g/cm&lt;sup&gt;3&lt;/sup&gt;, 0.03–5 eV). The FTRDFT overestimates the density effect on the line shift, while TSHFS underestimates the density effect. The future work will focus on optimizing the experimental method of X-ray fluorescence spectroscopy, obtaining X-ray fluorescence spectrum of titanium with more states, and then testing the theoretical method for warm dense matter.

Study of experimental method for warm dense matter ionization distribution based on x-ray fluorescence spectroscopy

Warm dense matter (WDM), a state of matter which lies at the frontiers between condensed matter and plasma, is one of the main research objects of high energy density physics (HEDP). Compared to the isolated atom, the electron structure of WDM will change because of the influence of density and temperature effect. Both the accurate theoretical represent and the accurate experimental study of WDM electron structure are challenging, as it is strongly coupled and partially degenerated. In this paper, an experimental method for studying the ionization distribution of warm dense matter based on x-ray fluorescence spectroscopy is developed. In the experiment, warm dense titanium with several tens eV and near solid density is created by a simultaneous drive from high energy xray heating and shock compression in a special designed hohlraum. Then, using the characteristic line spectrum emitted by the laser irradiation on pump material (Vanadium) as pump source, the titanium emits fluorescence. The x-ray fluorescence spectroscopy of titanium with different states (cold sample, 1.8-4.5 g/&lt;i&gt;cm&lt;/i&gt;&lt;sup&gt;3&lt;/sup&gt; and 1-25 eV) is diagnosed by changing the experimental strategy. The experimental results indicate that the line profiles of &lt;i&gt;K&lt;sub&gt;α&lt;/sub&gt;&lt;/i&gt; and &lt;i&gt;K&lt;sub&gt;β&lt;/sub&gt;&lt;/i&gt; fluorescence spectrum of the heated sample change obviously relative to that of the cold sample. Associating a theoretical calculation from two-step Hartree-Fock-Slater (TSHFS) method, the reason for the variation of the line profile is the change of ionization distribution mainly caused by temperature rise. The future work will focus on optimizing the experimental method of x-ray fluorescence spectroscopy, such as improving the spectrum resolution, characterizing the temperature and density experimentally, obtaining a set of ionization distribution data, and then study the influence of dense environment on electronic structure.