Fluorescence Emission Spectroscopy Research Articles

Characterization and classification of pathogenic bacteria using native fluorescence and spectral deconvolution.

Identification and classification of pathogenic bacterial strains is of current interest for the early treatment of diseases. In this work, protein fluorescence from eight different pathogenic bacterial strains were characterized using steady state and time resolved fluorescence spectroscopy. The spectral deconvolution method was also employed to decompose the emission contribution from different intrinsic fluorophores and extracted various key parameters, such as intensity, emission maxima, emission line width of the fluorophores, and optical redox ratio. The change in average lifetime values across different bacterial strains exhibits good statistical significance (p ≤ 0.01). The variations in the photophysical characteristics of bacterial strains are due to the different conformational states of the proteins. The stepwise multiple linear discriminate analysis of fluorescence emission spectra at 280 nm excitation across eight different bacterial strains classifies the original groups and cross validated group with 100% and 99.5% accuracy, respectively.

Monitoring the Quality Parameters of Mango Juices Using Fluorescence Spectroscopy.

The current study looks into the characterization and differentiation of mango juices that are sold commercially using fluorescence spectroscopy. The emission spectra displayed well-defined and prominent peaks that suggested the existence of many fluorophores, such as water content, β-carotene, tartrazine food color, and chlorophyll components. For this study, water and yellow food coloring solution, the two most popular adulterants were added to pure and authenticated mango pulp that had been diluted to an 8% concentration. The fluorophore profile of the samples was ascertained by using multivariate analysis (principal component analysis) in conjunction with fluorescence spectroscopy. The findings showed that the existence of water content is directly correlated with the spectral bands at 444 and 467nm, and for food color at 580nm thus the best indicators to detect adulteration of high water contents and food color. Chlorophyll and β-carotene intensities varied among juices, acting as a discriminant marker to distinguish between those with unripened pulp (high chlorophyll intensity) and those with more water and other pigments (lower chlorophyll and β-carotene intensities). With fluorescence emission spectroscopy, qualitative assessment of mango juice can be quickly determined by spectral features, providing details on composition and quality.

A rapid method to monitor structural perturbations of high-concentrated therapeutic antibody solutions using Intrinsic Tryptophan Fluorescence Emission spectroscopy

Drug product development of therapeutic antibody formulations is still dictated by the risk of protein particle formation during processing or storage, which can lead to loss of potency and potential immunogenic reactions. Since structural perturbations are the main driver for irreversible protein aggregation, the conformational integrity of antibodies should be closely monitored. The present study evaluated the applicability of a plate reader-based high throughput method for Intrinsic Tryptophan Fluorescence Emission (ITFE) spectroscopy to detect protein aggregation due to protein unfolding in high-concentrated therapeutic antibody samples. The impact of fluorophore concentration on the ITFE signal in microplate readers was investigated by analysis of dilution series of two therapeutic antibodies and pure tryptophan. At low antibody concentrations (< 5 mg/mL, equivalent to 0.8 mM tryptophan), the low inner filter effect suggests a quasi-linear relationship between antibody concentration and ITFE intensity. In contrast, the constant ITFE intensity at high protein concentrations (> 40 mg/mL, equivalent to 6.1 mM tryptophan) indicate that ITFE spectroscopy measurements of IgG1 antibodies are feasible in therapeutically relevant concentrations (up to 223 mg/mL). Furthermore, the capability of the method to detect low levels of unfolding (around 1 %) was confirmed by limit of detection (LOD) determination with temperature-stressed antibody samples as degradation standards. Change of fluorescence intensity at the maximum (ΔIaM) was identified as sensitive descriptor for protein degradation, providing the lowest LOD values. The results demonstrate that ITFE spectroscopy performed in a microplate reader is a valuable tool for high-throughput monitoring of protein degradation in therapeutic antibody formulations.

Optimizing Green Synthesis of Hydrotalcite - Silver Nanoparticles using Syzygium Nervosum based Reducing Agent.

Hydrotalcite-silver (HT-Ag) nanoparticles have been involved in various daily crucial applications, such as antibacterial, photocatalytic, adsorption, etc. There are many approaches to synthesizing silver nanoparticles (AgNPs) decorated on hydrotalcite (HT) surface and the most used approach is using a strong reducing agent. Thus, affordable but effective "green" reducing agents - Syzygium nervosum leaf extract, are taken into account in this work to solve several issues related to chemical reducing agents. This work aimed to assess the effect of Syzygium nervosum leaf extract as a reducing agent for green synthesis of AgNPs on HT through an optimizing process using response surface methodology (RSM) and the Box-Benken model. The optimal conditions for the synthesis of AgNPs on HT include a reaction time of 6.15 hours, a reaction temperature of 50 °C, and the ratio of diluted Syzygium nervosum leaf extract to reduce AgNO3 of 50.37 mL/mg. Under the optimal conditions, the yield of the reduction reaction reached 77.54 %, close to the theoretical value of 76.97 %. The optimization model was suitable for the experiment data. Besides, the morphology, density, and characteristics of AgNPs on the surface of HT layers have been determined by using Ultraviolet-visible spectroscopy, Field emission scanning electron microscopy (FESEM), High-resolution transmission electron microscopy (HR-TEM), selected area diffraction, X-ray diffraction, Dynamic light scattering (DLS), Infrared (IR) spectroscopy, Fluorescence emission spectroscopy (FE), Brunauer-Emmett-Teller (BET) methods. The spherical AgNPs were synthesized successfully on the surface of HT with the average particle size of 13.0±1.1 nm. Interestingly, HT-Ag hybrid materials can inhibit strongly the growth of E. coli, S. aureus as well as two antibiotic resistance bacterial strains, P. stutzeri B27, and antibiotic resistance E. coli. Especially, the antibacterial activity quantification and durability of the HT-Ag hybrid materials were also tested. Overall, the HT-Ag hybrid materials are very promising for application in material science and biomedicine fields.

Construction of Spin Crossover‐Fluorescent Bifunctional Cyclic Chain‐Like Fe(II) Compounds from Carbazole Ligands

AbstractThe incorporation of fluorescent properties into spin‐crossover (SCO) materials, aiming at controlling fluorescence via spin‐state transitions for applications in magneto‐optical switching and information processing, represents an appealing research direction. In this study, we prepared two examples of one‐dimensional cyclic chain‐like Fe(II) coordination polymers, denoted as [Fe(DPPC)2(NCS)2]⋅CH3OH⋅o‐C6H4Cl2 (1, DPPC=3,6‐di‐4‐pyridinyl‐9‐[4‐(4‐pyridinyl)phenyl]‐9H‐carbazole) and [Fe(PDPC)2(NCS)2] (2, PDPC=3,6‐di(pyridin‐4‐yl)‐9‐phenyl‐9H‐carbazole). Analyses through single‐crystal X‐ray studies and magnetic measurements validate the two‐step SCO behavior of 1 within the temperature range of 50~200 K. Additionally, when combined with temperature‐dependent fluorescence emission spectroscopy, the results demonstrate the coexistence of SCO and fluorescence in 1.

Design, Preparation, and Interfacial Adhesion of Polystyrene‐Based Luminophore Elastomers Based on Bionic Strategy

AbstractA series of rigid polystyrene‐based photoelastomers, named sty‐PM‐x, with bionic catechol pendants were synthesized through atom transfer radical polymerization (ATRP) and deprotection techniques. These polymers were characterized using nuclear magnetic resonance spectroscopy, gel permeation chromatography, and thermogravimetric analysis. Additionally, photophysical properties of the polymers were investigated using UV‐visible absorption spectroscopy and fluorescence emission spectroscopy. Mechanical properties were evaluated through tensile tests, while interfacial adhesion was determined through cross‐cut tests. Experimental results reveal that photoelastomers, sty‐PM‐x, exhibit excellent photophysical properties, stretchability, and interfacial adhesion. This discovery provides a new perspective for the preparation of stretchable organic electroluminescent materials.

Exploring the multi-faceted potential: Synthesized ZnO nanostructure – Characterization, photocatalysis, and crucial biomedical applications

This research describes the methodology for synthesizing zinc oxide nanoparticles (ZnO-NPs). It demonstrates a unique, cost-effective, and non-toxic chemical technique for producing ZnO-NPs using the precipitation method with NaOH as reducing and capping agents. The formed nanoparticles have been characterized and analyzed using numerous techniques such as; Fluorescence emission spectroscopy (FL), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray Spectroscopy (EDX), ultraviolet–visible optical absorption (UV–Vis), Fourier transform infrared spectroscopy (FTIR), and Thermal gravimetric analysis (TGA). Also, the analytical technique X-ray diffraction studies has been used which showed that the ZnO-NPs had a Wurtzite hexagonal crystal structure with an average crystallite size of 34.27 nm. The form and the size of the synthesized ZnO-NPs have been seen in SEM and TEM photographs. Using J-image, particle size has been obtained at 13.33 nm, and the grain boundaries were all approximately spherical. Peaks in the FT-IR spectrum of the NPs indicate the presence of carboxylate (COO) and hydroxyl (O–H) functional groups. According to these findings, Zn interstitial defects are responsible for the 380 nm emission peak. Since EDX could not identify any impurities below the detection threshold, we may be sure that Zn and O are the principal components of the synthesized sample. ZnO-NPs cause an absorption band at 350.34 nm in the UV–Vis spectrum and a band gap of 3.24 eV. The catalytic activity of the synthesized ZnO nanoparticles (NPs) was evaluated by investigating their effectiveness in degrading crystal violet (CV) and methylene blue (MB) dyes, along with assessing the degradation rates. The results demonstrated a high degradation efficiency, with ZnO NPs achieving approximately 96.72 % degradation for CV and 97.169 % for MB dyes, underscoring their remarkable efficacy in the degradation process. As for antimicrobial activity assessment, the results revealed that the ZnO-NPs had negligible impact on Gram-negative bacteria, whereas they exhibited a discernible effect on Gram-positive bacteria. Additionally, it showed anti-cancer potential against colon (SW480), breast (MDA-231), and cervix (HELA) lines cells as seen by (MTT) assay. Hence, due to its simplified processes and cheaper chemicals, our synthesis technique may use in industrial settings for various applications.

Octenyl succinylation of myofibrillar protein: Structural, physicochemical and emulsifying properties

In this study, different succinylation degree octenyl succinic anhydride modified myofibrillar protein (OSA-modified MP) were prepared through succinylation modification by adding various OSA (1%, 3%, 6%, 11%, 16%, 21% and 26% of the weight of MP) to MP. The structure, physicochemical properties and emulsifying properties of OSA-modified MP were investigated. Results showed that succinylation degree of the modified protein rose from 1.46% to 94.99%. Electrophoresis, fourier transform infrared spectroscopy, intrinsic tryptophan fluorescence emission spectroscopy and scanning electron microscopy demonstrated the structure of MP was changed. As the DS increased, the particle size decreased by the maximum values of 0.24 times, the surface net charge and solubility increased by the minimum values of 2.71 and 13.50 time, respectively. All these results caused emulsifying activity and emulsifying stability to increase by 2.32 and 1.46 times, respectively, indicated that succinylation greatly improved the emulsifying properties of MP. Compared to the native MP, OSA-modified MP was more beneficial to stabilize Pickering emulsion. Thus, succinylation improved the emulsifying properties of MP and effectively expanded the application range of MP in the food industry.

Preparation, structure and spectral characteristics of Zinc tellurite glasses system doped with different concentrations of Tm3+

Gallium-tellurite glass is a new optical material with good transmittance in the infrared region up to 6.5[Formula: see text][Formula: see text]. Three different tellurate glasses were prepared: TeO2–ZnO–Ga2O3(TZG), TeO2–ZnO–La2O3(TZL) and TeO2–ZnO–B2O3(TZB). X-ray diffraction indicates that no crystal precipitates in the three glass systems, which maintain a stable glass state. Raman scattering experiments and fluorescence emission spectroscopy measurements were carried out on the tellulate glasses doped with the same concentration of Tm[Formula: see text]. It was found that the phonon energy of TZG(TeO2–ZnO–Ga2O3)-doped thulium glass is the lowest, and the emission light at 1380[Formula: see text]nm is the strongest with [Formula: see text][Formula: see text]nm fluorescence FWHM. These results show that Tm-doped TZG glass is a good luminescent material. Refractive indices were measured by the minimum deviation method. Sellmeier dispersion equation is obtained, which can be used to calculate the refractive index within visible and near-infrared spectral range. Furthermore, different Tm[Formula: see text] concentrations (0.4%, 0.8%, 1.2% and 2%) TZG glasses were prepared, the emission spectra and fluorescence lifetime were measured, and the emitted light was strongest when the thulium ion doping concentration is 1.2%. All the results suggest that these newly developed ternary tellurite glass systems are promising candidates for near/mid-infrared laser glass fibers, fiber amplifiers, or lasers.

Gallium(III) complexes with 1,3-pdta-type of ligands: The influence of an alkyl substituent in 1,3-propanediamine chain and the metal counter cation on the structural properties of the complex

The hexadentate 1,3-propanediamine-N,N,N’,N’-tetraacetate (1,3-pdta4−) and (±)-1,3-pentanediamine-N,N,N’,N’-tetraacetate (1,3-pndta4−) ligands were used for the synthesis of two new gallium(III) complexes, Na[Ga(1,3-pdta)]·3H2O (1) and Ba[Ga(1,3-pndta)]2·3H2O (2). Complexes 1 and 2 were characterized by IR and NMR (1H and 13C) spectroscopy and single crystal X-ray diffraction analysis. The obtained results have shown that both hexadentate 1,3-pdta4− and 1,3-pndta4− ligands are coordinated to gallium(III) ion through the two nitrogen and four carboxylate oxygen atoms. Both complexes show significant octahedral distortion since the mean angular deviation is nearly four degrees per angle. However, the octahedral distortion of complex 2 is lower than of 1, as indicated by the ΣΔ(Oh) values (48° and 49° versus 53°, respectively). The binding interactions of the complexes 1 and 2 with calf thymus DNA (ct-DNA) and bovine serum albumin (BSA) were studied by fluorescence emission spectroscopy. Both complexes can bind to the serum albumin reversibly, while their affinity to ct-DNA is rather low.

Classifying PDO Kalamata Olive Oil from Geographic Origins of the Messenia Region based on Statistical Machine Learning

Kalamata is a smart city located in southeastern Greece in the Mediterranean basin and it is the capital of the Messenia regional unit. It is known for the famous Protected Designation of Origin (PDO) Kalamata olive oil produced mainly from the Koroneiki olive variety. The PDO Kalamata olive oil, established by Council regulation (EC) No 510/2006, owes its quality and special characteristics to the geographical environment, olive tree variety, and human factor. The PDO Kalamata olive oil is produced exclusively in the regional unit of Messenia, being the main profit of local farmers. However, soil chemical composition, microclimates, and agronomic factors are changed within the Messenia spatial area leading to differentiation of PDO Kalamata olive oil characteristic. In this paper, we use statistical machine learning algorithms to determine the geographical origin of Kalamata olive oil at PDO level based on synchronous excitation−emission fluorescence spectroscopy of olive oils. Evaluations of the statistical models are promising for differentiating the origin of PDO Kalamata olive oil with high values of prediction accuracy thus enabling companies that process and bottle kalamata olive oil to choose olive oil from a specific region of Messenia that fulfills certain characteristics. Concretely, the current research effort focuses on a specific olive oil variety within a limited geographic region. Intuitively, future research should also focus on validation of the proposed methodology to other olive oil varieties and production areas.

Synthesis, characterization, biological potency, and molecular docking of Co2+, Ni2+ and Cu2+ complexes of a benzoyl isothiocyanate based ligand

The primary objective of the present study was to produce metal complexes of H4DAP ligand (N,N'-((pyridine-2,6-diylbis(azanediyl))bis(carbonothioyl))dibenzamide) derived from 2,6-diaminopyridine and benzoyl isothiocyanate with either ML or M2L stoichiometry. There are three distinct coordination complexes obtained with the formulas [Co(H2DAP)]·H2O, [Ni2(H2DAP)Cl2(H2O)2]·H2O, and [Cu(H4DAP)Cl2]·3H2O. The confirmation of the structures of all derivatives was achieved through the utilization of several analytical techniques, including FT-IR, UV–Vis, NMR, GC–MS, PXRD, SEM, TEM analysis, and QM calculations. Aiming to analyze various noncovalent interactions, topological methods such as QTAIM, NCI, ELF, and LOL were performed. Furthermore, the capacity of metal–ligand binding was examined by fluorescence emission spectroscopy. An in vitro investigation showed that the viability of MDA-MB-231 and HepG-2 cells was lower when exposed to the manufactured Cu2+ complex, in comparison to the normal cis-platin medication. The compounds were further evaluated for their in vitro antibacterial activity. The Ni2+ complex has shown promising activity against all tested pathogens, comparable to the reference drugs Gentamycin and Ketoconazole. Furthermore, a computational docking investigation was conducted to further examine the orientation, interaction, and conformation of the recently created compounds on the active site of the Bcl-2 protein.

Preparation and sensing performance study in ultra-wide temperature range of K3LuF6:Er3+,Yb3+ up-converting luminescent materials with cryolite structure

Cryolite-type materials have advantages of low phonon energy, easy rare-earth ion doping, and stable physicochemical properties, and they are considered ideal matrices for up-converting luminescent materials. In this paper, a series of K3LuF6:Er3+,Yb3+ up-converting materials with cryolite structure were prepared for the first time by high-temperature solid-phase method. The compositions, structures and luminescent properties were systematically characterized by X-ray powder diffractometry (XRD), field emission scanning electron microscopy (SEM) and fluorescence spectroscopy (PL). Under 980 nm excitation, the sample emission spectra mainly consisted of green and red emission bands with peaks at 525, 546 and 662 nm, corresponding to the 2H11/2-4I15/2, 4S3/2-4I15/2 and 4F9/2-4I15/2 electron transitions of Er3+, respectively. In addition, the temperature sensing characteristics of two thermally coupled energy levels (2H2/11 and 4S3/2) were studied based on the fluorescence intensity ratio (FIR) technique in the range of 79–579 K. All the results show that K3LuF6:Er3+/Yb3+ up-converting luminescent materials have excellent temperature sensing performance in the ultra-wide temperature range and have broad application prospects in the field of temperature sensing.

Development of a high throughput oxidation profiling strategy for monoclonal antibody products

Oxidation is one of the most common degradation pathways of biopharmaceutics, potentially leading to altered product stability, pharmacokinetics, reduced biological activity and/or an increased immunogenicity. However, it is often insufficiently assessed in early development stages, leaving potential molecule liabilities undiscovered. Aim of the present work was the development of a high throughput oxidation profiling strategy, applicable throughout various stages of biopharmaceutical development. The study demonstrates that the combination of multiple stress assays, including peroxide-based, visible light, and metal-catalyzed oxidation (MCO), enables a comprehensive understanding of a mAb's oxidation susceptibility. The most effective parameters to evaluate oxidation in a high-throughput screening workflow are aggregation, tryptophan oxidation and changes in the hydrophobicity profile of the Fc and Fab subunit measured via Size Exclusion Chromatography, Intrinsic Tryptophan Fluorescence Emission spectroscopy and Reversed-Phase Chromatography subunit analysis, respectively. This oxidation profiling approach is valuable tool to systematically characterize the oxidation susceptibility under relevant conditions, time effective and with minimal sample consumption.

Poly(triphenylamine-thiazolo[5,4-d]thiazole) copolymer dyes with different anchoring end groups: Synthesis, dye-sensitized solar cell (DSSC) performance and femtosecond excited state absorption spectroscopy

In this study, the poly(triphenylaminethiazolo[5,4-d]thiazole) copolymer dyes having the different anchoring end groups of aldehyde (poly-TPATT-CHO; P5), sulfonic acid (poly-TPATT-SO3H; P5S) and cyanoacrylic acid (poly-TPATT-COOH; P5C) have been synthesized and used as sensitizers in dye-sensitized solar cells (DSSCs). The effects of the anchoring end groups of the P5, P5S and P5C copolymer dyes on the DSSC performance were examined. The synthesized copolymer dyes were characterized using 1H NMR, UV–vis. absorption and fluorescence (FL) emission spectroscopy, cyclic voltammetry (CV), MALDI-TOF-MS and FE-SEM-EDS methods. Among the studied polymers, the P5C polymer dye exhibited the best photovoltaic performance with a JSC of 6.46 mA cm−2, a VOC of 0.667 V, a FF of 0.70, and an overall power conversion efficiency (PCE) of 3.02 % under standard AM 1.5 G solar light conditions. These results are attributed to the strong binding ability of cyanoacrylic acid to the TiO2, leading to a greater photocurrent and hindered charge recombination. The effect of electron transfer mechanisms of the polymers on the DSSC performance have been investigated using the femtosecond transient absorption (fs TA) spectroscopy. The DSSC performance of the poly(triphenylaminethiazolo[5,4-d]thiazole) increased greatly by the presence of the cyanoacrylic acid anchoring end group in P5C polymer dye. The fs TA spectroscopy results revealed the presence of singlet–triplet transition for the P5C copolymer dye, while the P5 and P5S copolymers showed only singlet–singlet transitions. The observed triplet state transition in the P5C polymer increased the yield of the DSSC system.

Synthesis and Application of Specific N2H4 Fluorescent Probes with AIE Effect Based on Pyrazole Structure.

Two fluorescent probes, Y1-2 were synthesized from 2-acetonaphthone, 4-acetylbiphenyl, and phenyl hydrazine by Vilsmeier-Haack reaction and Knoevenagel condensation. Their recognition efficacies for N2H4 were tested by UV-visible absorption spectroscopy and fluorescence emission spectroscopy. The recognition mechanism were studies by density-functional theory calculations, and the effect of pH on N2H4 recognition was also studied. The results showed that the probe Y1-2 has high selectivity and a low detection limit for N2H4, and the recognition of N2H4 can be accomplished at physiological pH. The probes have had obvious aggregation-induced luminescence effect, large Stokes shift, high sensitivity, and can be successfully applied to live cell imaging.

Inactivation of polyphenol oxidase by low intensity DC field: Experiment and mechanism analysis via molecular dynamics simulation and molecular docking

In this study, inactivation of mushroom polyphenol oxidase (PPO) by low intensity direct current (DC) electric field and its molecular mechanism were investigated. In the experiments under 3 V/cm, 5 V/cm, 7 V/cm and 9 V/cm electric fields, PPOs were all completely inactivated after different exposure times. Under 1 V/cm, a residual activity of 11.88 % remained. The inactivation kinetics confirms to Weibull model. Under 1–7 V/cm, n value closes to a constant about 1.3. The structural analysis of PPO under 3 V/cm and 5 V/cm by fluorescence emission spectroscopy and molecular dynamics (MD) simulation showed that the tertiary structure was slightly changed with increased radius of gyration, higher potential energy and rate of C-alpha fluctuation. After exposure to the electric field, most of the hydrophobic tryptophan (TRP) residues turned to the hydrophilic surface, resulting the fluorescence red-shifted and quenched. Molecular docking indicated that the receptor binding domain of catechol in PPO was changed. PPO under electric field was MD simulated the first time, revealing the changing mechanism of the electric field itself on PPO, a binuclear copper enzyme, which has a metallic center. All these suggest that the low intensity DC electric field would be a promising option for enzymatic browning inhibition or even enzyme activity inactivation.

Monitoring of DNA structural changes after incorporation of the phenylpyrazole insecticide fipronil

The use of insecticides presents a risk to the environment because they can accumulate in the water, soil, air, and organisms, endangering human and animal health. It is therefore essential to investigate the effects of different groups of insecticides on individual biomacromolecules such as DNA. We studied fipronil, which belongs to the group of phenylpyrazole insecticides. The interaction of fipronil with calf thymus DNA was investigated using spectroscopic methods (absorption and fluorescence spectroscopy) complemented with infrared spectroscopy and viscosity measurement. Fluorescence emission spectroscopy showed the formation of a fipronil/DNA complex with a combined static and dynamic type of quenching. The binding constant was 4.15 × 103 L/mol. Viscosity changes were recorded to confirm/disconfirm the intercalation mode of interaction. A slight change in DNA viscosity in the presence of fipronil was observed. The phenylpyrazole insecticide does not cause significant conformational changes in DNA structure or increase of its chain length. We hypothesize that fipronil is incorporated into the minor groove of the DNA macromolecule via hydrogen interactions as indicated by FT-IR and CD measurements.

Effects of ultraviolet radiation and reactive oxygen species on the structure and ligand-binding ability of human serum albumin for norfloxacin

To explore the influence of ultraviolet radiation (UV) and reactive oxygen species (ROS) on the structure and ligand-binding ability of human serum albumin (HSA) for norfloxacin (NFLX), HSA was treated with UV (HSAUV) and UV/H2O2 (HSAUV/H2O2), respectively. The structure difference of HSA, HSAUV and HSAUV/H2O2 were investigated by Fourier transform infrared, fluorescence (i.e., emission fluorescence, synchronous fluorescence and fluorescence lifetime) and circular dichroism spectroscopy. The intermolecular interactions of HSA, HSAUV and HSAUV/H2O2 with NFLX were studied at pH 7.4 and temperatures 291, 310, and 318 K, using fluorescence emission and synchronous fluorescence spectroscopy, and combined with molecular docking. The results suggested that UV and ROS could destroy the α-helix of HSA and induce the loose of HSA structure, and the average fluorescence lifetimes of HSA decreased from 6.12 ns to 3.76 ns (HSAUV) and 3.40 ns (HSAUV/H2O2). The conformational changes of HSA caused by UV and ROS allowed NFLX to get access to more potential binding sites and promoted the binding affinity of HSA for NFLX, while the temperature stability of the HSA-NFLX complex significantly decreased. The results are useful and valuable for evaluating the protein damage caused by UV and ROS in organisms.

Insights into the binding of buspirone to human serum albumin using multi-spectroscopic and molecular docking techniques

Buspirone is an anxiolytic drug that plays a significant role in managing anxiety disorders and alleviating their symptoms as well. Several techniques were utilized to study the interaction between buspirone and human serum albumin under physiological conditions, including UV–vis absorption spectroscopy, fluorescence emission spectroscopy, circular dichroism, Fourier transform infrared spectroscopy (FT-IR), equilibrium dialysis, and molecular docking. The results of this study demonstrated that buspirone quenched the intrinsic fluorescence of human serum albumin through a mixed mechanism. Moreover, the binding constants (Kb), the quenching constants (Ksv), and thermodynamic parameters were calculated at various temperatures. The binding process of buspirone to human serum albumin showed a cooperative binding pattern, confirmed by the Scatchard diagram and Hill coefficient. Molecular docking results showed that buspirone interacted with the IIA, IIIA, and IIB subdomains of human serum albumin and slightly changed its conformation. It was also found that hydrophobic forces played a major role in this interaction. This study consequently proves that BSH as a drug can be transported by blood albumin. Additionally, due to its ratiometric response in absorbance upon binding to a biological target, HSA can be used as a molecular probe to follow biomolecular interactions.