Synchronous Fluorescence Spectra Research Articles

First derivative synchronous spectrofluorimetric analysis of bisoprolol fumarate and ivabradine in pharmaceutical and biological matrices. Investigation of the method greenness.

A novel, facile, rapid, and precise synchronous spectrofluorimetric method was evolved for the simultaneous estimation of bisoprolol fumarate and ivabradine in dosage forms and biological fluids. The estimation is based on measuring the first derivative of the synchronous fluorescence spectra of ivabradine and bisoprolol fumarate in ethanol at Δλ = 80 nm. The peak amplitudes are measured at 234.4nm (zero-crossing point of ivabradine) and 244.0nm (zero-crossing point of bisoprolol fumarate) to simultaneously analyze bisoprolol fumarate and ivabradine, respectively. The spectrofluorimetric method was optimized by investigating different solvent systems, pH values, and surfactants. The proposed method was linear over concentration ranges 30.0-200.0ng/ml and 30.0-180.0ng/ml for ivabradine and bisoprolol fumarate, respectively with detection limits of 4.88 and 5.28 ng/ml. The developed method was used for individual assay of the studied compounds in their pharmaceutical dosage forms with high percentage recoveries. Moreover, the method was applied to analyze ivabradine and bisoprolol fumarate in spiked human urine with percentage recoveries of 99.98 ±1.16 and 99.95 ±1.96 for ivabradine and bisoprolol fumarate, respectively. The method greenness was also investigated by Analytical GREEnness (AGREE), Analytical Eco-Scale, and Green Analytical Procedure Index (GAPI) metrics, which ensured the ecofriendship of the proposed method.

Effects of different particle-sized insoluble dietary fibre from citrus peel on adsorption and activity inhibition of pancreatic lipase

Insoluble dietary fibre from citrus peels (CIDF) was found to have adsorption and inhibitory effect on the activity of pancreatic lipase (PL). CIDF-400 exhibited the greatest adsorption and activity inhibition effect on PL. The fluorescence quenching spectra indicated that CIDF could quench PL through a dynamic quenching process induced by the electrostatic interactions with only one binding site between them. The synchronous fluorescence and three-dimensional fluorescence spectra showed that CIDF might combine with PL to induce the increase in hydrophobicity and the reduction in polarity of tyrosine (Tyr) and tryptophan (Try) residues, which further led to the conformational alternations of PL. Moreover, circular dichroism (CD) showed that CIDF altered the secondary structure of PL, decreased α-helical structure content, and increased β-sheet structure content, potentially resulting in PL structure opening and its active site exposure. This study provides new perspectives for the application of CIDFs produced from agricultural waste in regulating lipid metabolism.

The effect of arginine on inhibiting amyloid fibril derived from β-casein and the binding studies with multi-spectroscopic techniques

In general, β-casein is a stable molecular chaperone. However, the fact that amyloid fibrils derived from β-casein has been reported in some cases, which were usually associated with some malignant breast diseases. As an important amino acid, arginine not only exhibits the significance in casein synthesis in mammary gland, but also has great potentiality in inhibiting the amyloid fibril formation. Therefore, the influence of arginine on the amyloid fibrils formed by β-casein and further molecular mechanism were studied firstly with multi-spectroscopic techniques in the present work. The results of Thioflavin T determination, particle size analysis, transmission electron microscope observation showed that arginine not only inhibited the aggregation of β-casein at the growth stage, but also depolymerized the mature amyloid fibrils at the saturation stage. The further fluorescence experiment results demonstrated that the complex was formed between β-casein and arginine. Besides, there was one binding site and 0.48 nm binding distance. The thermodynamic parameters like ΔG0, ΔS0, ΔH0 were all negative, showing their binding reaction was spontaneous, and hydrogen bond and van der Waals force were the possibly chief intermolecular forces. Furthermore, the synchronous fluorescence spectra showing that the conformation of β-casein was affected and its tyrosine residues were gradually buried inside the protein. Our research would provide new insights into the treatments for the breast amyloidosis.

Structural elucidation, in vitro DNA binding and anticancer investigations of a new specific target dinuclear Zn(II) complex

In this study, dinuclear bis(2,2′-bipyridine)-tris{[μ-pyrimidin-2-yl)sulfanyl]acetato}Zn(II) perchlorate complex was synthesized and characterized by FT-IR, ESI-MS, 1H NMR and single-crystal X-ray diffraction studies. The bis(2,2′-bipyridine)-tris{[μ-pyrimidin-2-yl)sulfanyl]acetato}Zn(II) perchlorate was crystallized in a monoclinic crystal system having a P 21/c space group. The single-crystal structure of bis(2,2′-bipyridine)-tris{[μ-pyrimidin-2-yl)sulfanyl]acetato}Zn(II) perchlorate reveals that Zn1 is five coordinated and has adopted distorted square pyramidal geometry while as Zn2 centre is six coordinated and has adopted distorted octahedral geometry, bridged by three carboxylate groups of (2-pyrimidylthio) acetic acid (PTAA). Hirshfeld surface analysis and density functional theory were determined by crystallographic computational tools to investigate the contribution of non-covalent interactions, reactivity and stability of bis(2,2′-bipyridine)-tris{[μ-pyrimidin-2-yl)sulfanyl]acetato}Zn(II) perchlorate. In vitro, ct-DNA binding studies of the complex were accomplished by applying various spectroscopic and analytical techniques. The results obtained suggested a groove or electrostatic mode of binding. The bis(2,2′-bipyridine)-tris{[μ-pyrimidin-2-yl)sulfanyl]acetato}Zn(II) perchlorate has caused significant double-stranded scission of pBR322 DNA through the hydrolytic pathway as observed by the gel electrophoretic experiment. Cytotoxicity of bis(2,2′-bipyridine)-tris{[μ-pyrimidin-2-yl)sulfanyl]acetato}Zn(II) perchlorate was evaluated against MCF-7, MDA-MB-231, Hop-62, AW13516 and SiHa human cancer cell lines, which revealed a moderate anticancer response. In addition, binding studies of the bis(2,2′-bipyridine)-tris{[μ-pyrimidin-2-yl)sulfanyl]acetato}Zn(II) perchlorate with BSA protein were performed by fluorescence spectroscopy. The synchronous fluorescence spectra suggested the efficient binding of complex towards tyrosine than tryptophan. The quenching mechanism of BSA by complex was found static in nature.

FLUORESCENCE STUDIES ON THE BLOOD PLASMA ALBUMIN INTERACTION WITH 4-HYDROXY-2-METHYLQUINOLINE

Blood plasma albumin (bovine serum albumin, BSA) interaction with a biologically active reagent 4-hydroxy-2-methylquinoline (4H2MQ) has been studied using fluorescence spectroscopy methods (steady state, synchronous, excitation/emission matrix, 3D spectra). With the addition of 4H2MQ, no changes in the spectral characteristics of BSA (fluorescence emission intensity and λmax position) are observed; only the symmetry of the BSA emission spectrum is changed and the full width at half maximum is decreased. The analysis of synchronous and 3D fluorescence spectra showed the existence of three emitting species in this system, which could be a result of changes in the fluorescence and photochemical properties of 4H2MQ.

Binding effects of antibiotic drug sulfamethazine on the serum albumins: Multi-spectroscopic and computation approach

Over the past decades, bio-macromolecules-drug binding interaction studies have been of great interest with varied applications in drug modification and development. Such reports help us to recognize the molecular aspects of the bindings correlating with the structural phenomenon. The binding study of an antibiotic drug, Sulfamethazine (SMZ) with plasma proteins, Human Serum Albumin (HSA), and Bovine Serum Albumin (BSA) have been investigated using spectroscopic and computational techniques. The UV–Vis and fluorescence spectroscopic data indicate towards potential binding affinity of the drug to the proteins through the formation of stable ground state complexes. Binding constants obtained were in the order of 104M − 1 for both the cases, the values were comparatively higher for HSA than BSA. Thermodynamic parameters were estimated from temperature-dependent fluorescence analyses; enthalpy driven, exothermic nature of the binding interactions along with the predominance of electrostatic and hydrophobic forces were established in both the cases. Synchronous fluorescence and FT-IR spectra revealed the conformational changes in the protein structure(s). Molecular docking and dynamic studies further supported the complex formation in accordance with the experimental report(s). Molecular docking denoted binding of the drug at pocket-I of the active site in proteins, while molecular dynamic simulation established the stability and compactness of the complex due to binding.

Utility of synchronous fluorimetry for the concurrent quantitation of metoprolol and ivabradine

Metoprolol combined with ivabradine have been determined up to nanogram level simultaneously relied on the synchronous fluorescence spectra. First derivative amplitudes of the synchronous spectrofluorimetric spectra are recorded at Δλ = 40 nm using ethanol as diluting solvent. Metoprolol can be measured at 286 nm which is the zero-crossing point of ivabradine, and the later can be measured at 296 nm. The calibration plots were found to be linear over the ranges of concentrations: 100.0–1000.0 ng/mL and 10.0–200.0 ng/mL for metoprolol and ivabradine, respectively. Validation of the procedure was performed using the International Council of Harmonization guidelines. Values of LODs were found to be 28.89, 2.80 ng/mL and LOQs were 87.56, 8.49 ng/mL for metoprolol and ivabradine, respectively. As the two drugs are co-administered safely and effectively to reduce heart rate, angina attacks, the current methodology is utilized for the concurrent analysis of them in their single ingredient pharmaceutical preparations, synthetic mixtures, and biological fluids. The designed method, being cost-effective and simple procedure, is the first method for metoprolol and ivabradine simultaneous analysis. The results agreed statistically with the comparison methods.

Role of Seasons in the Fate of Dissolved Organic Carbon and Nutrients in a Large-Scale Surface Flow Constructed Wetland

The role of seasons in the removal of dissolved organic carbon (DOC), nutrients and in changes in the spectral properties of dissolved organic matter (DOM) in a large-scale surface flow constructed wetland (SF-CW) receiving reclaimed water and composed of three basins with different vegetation patterns was studied. Dissolved nitrogen removal efficiencies within the three basins in summer (>50%) and winter (<30%) were significantly different. SF-CW water is enriched in DOC in spring and summer with average outlet concentrations above 8 mg·L−1. UV-visible indices, such as the specific absorbance at 254 nm or the spectral slope between 275 and 295 nm, did not vary over the seasons; thus, the basins did not change DOM aromaticity and average molecular weight. Synchronous fluorescence spectra showed variations in terms of protein-like and humic-like substances, the latter being more sensitive to photodegradation. A lab-scale photodegradation experiment confirmed that radiation from the sun was responsible for this decrease, showing this process could alter the composition of DOM at full-scale. DOM variations result from a seasonal competition between release by vegetation and photodegradation. These results validate the necessity for long-term monitoring of SF-CWs, and the utility of rapid optical methods to monitor DOC.

Insight into the effects of biological treatment on the binding properties of copper onto dissolved organic matter derived from coking wastewater

Biological treatment can remove more than 89.8% of total organic carbon (TOC) and 94.4% of fluorescent dissolved organic matter (DOM) in the coking wastewater, thereby affecting the migration, transformation and bioavailability and binding characteristics of heavy metals (HMs). The results of parallel factor analysis (PARAFAC) show that protein-like materials accounted for 97.53% in the coking wastewater DOM, a large number of humic-like substances are produced and accounted for more than 55.40% after biological treatment. A new spectral data processing method, the 1/n-th power transformation after two-dimensional correlated spectroscopy (2D-COS) in combination with synchronous fluorescence spectra (SFS), can identify small features obscured by strong peaks, and reveal more binding sites as well as preserve the sequential order information. The result indicates that the preferential bonding of Cu(II) is at 306 nm (protein-like) for coking wastewater DOM, and at 514 nm (humic-like) for effluent DOM. The C−O group of esters and alcohols can preferentially complexate with Cu(II) in the coking wastewater and effluent DOM. The log KM values of PARAFAC components with Cu(II) are in the range of 3.59–5.06 for coking wastewater DOM, and in the range of 4.80–5.64 for the effluent DOM. Log KM values for protein-like materials with Cu(II) are higher than these for fulvic- and humic-like substances. Humic-like substances can form more stable complexes with Cu(II) in the effluent DOM. Biological treatment increases the chemical stability of DOM-Cu(II) complexes, thereby further reducing the environmental risk of Cu(II).

A fast and low-cost approach for the discrimination of commercial aged cachaças using synchronous fluorescence spectroscopy and multivariate classification.

Cachaça is the distilled beverage typical of Brazil and can be subjected to the aging process in wooden barrels. In addition to oak barrels, cachaça is also aged in barrels of different Brazilian native woods, resulting in a wide variety of its sensory characteristics. In this work, 172 cachaças aged in bálsamo, jequitibá, oak, and umburana barrels were analyzed by synchronous fluorescence spectroscopy and by the classification methods of principal component analysis and partial least squares discriminant analysis. Spectra were preprocessed by the first derivative by Savitzky-Golay smoothing, using a filter width and polynomial order determined through face-centered central composite designs. Multivariate analysis was realized using the spectra recorded at different wavelength differences, and models were compared by the classification errors in the test sets. The principal component analysis applied to the synchronous fluorescence spectra presented a tendency of separation by the wood used in the aging process, and the partial least squares discriminant analysis model constructed using the fluorescence spectra recorded at a wavelength difference of 30 nm provided better performance parameters (efficiency 91-97%, sensitivity 81-100%, and specificity 91-100%). Synchronous fluorescence spectroscopy offers a promising approach for the classification of cachaças aged in bálsamo, oak, jequitibá, and umburana barrels, and the discriminant model can be used for routine analysis as a screening method. © 2022 Society of Chemical Industry.

The discovery of berberine erythrocyte-hemoglobin self-assembly delivery system: a neglected carrier underlying its pharmacokinetics

Berberine (BBR) has extremely low concentration and high tissue distribution. However, current pharmacokinetic studies predominantly focus on its concentration in plasma, which could hardly make a comprehensive understanding of its pharmacokinetic process. This study made a pioneering endeavor to explore the erythrocyte-hemoglobin (Hb) self-assembly system of BBR by exploring the interaction of BBR with erythrocyte and the combination of BBR with Hb. Results showed that BBR had a low bioavailability (C0 = 2.833 μg/mL via intravenous administration of 2.5 mg/kg BBR and Cmax = 0.260 μg/mL via oral administration of 400 mg/kg BBR). Besides, BBR achieved higher concentrations in erythrocytes than plasma, and the erythrocytes count and Hb content were significantly decreased after intravenous administration. Hemolysis rate indicated the BBR-erythrocyte system (with 2% erythrocytes) was relatively stable without hemolysis at the concentration of 1.00 mg/mL. And the maximum percentage of drug loading was 100% when the BBR-erythrocyte concentration was 0.185 μg/mL. Furthermore, incubation of BBR and erythrocytes resulted in internalization of the erythrocyte membrane and the formation of intracellular vacuoles. The thermodynamic parameters indicated that the binding process of bovine hemoglobin (BHB) and BBR was spontaneous. UV-vis absorption spectra, synchronous fluorescence, circular dichroism and Raman spectra collectively indicated that BBR showed strong binding affinity toward BHB and affected the molecular environment of residues like tryptophan and tyrosine in BHB, resulting in the conformational changes of its secondary and tertiary structure. Molecular docking indicated BBR interacted with Arg-141 residue of BHB via hydrogen bond with the bond length of 2.55 Å. The ΔG value of the BHB-BBR system was −31.79 kJ/mol. Molecular dynamics simulation indicated the root mean square derivation of BBR-BHB was <0.025 nm, suggestive of stable conformation. Cumulatively, there was an erythrocyte-Hb self-assembled drug delivery system after oral or intravenous administration of BBR, which conceivably gained novel insight into the discrepancy between the extremely low plasma concentration and relatively high tissue concentration of BBR.

The activity and molecular interaction of lysozyme in adding four ionic liquids aqueous solutions

In this work, four hydrophilic ionic liquids (ILs, 1-butyl-3-methylimidazolium tetrafluoroborate ([C4mim]BF4), 1-butyl-3-methylimidazolium chloride ([C4mim]Cl), 1-butyl-3-methylimidazolium bromide ([C4mim]Br) and 1,3-dimethylimidazolium iodide ([dmim]I)) were selected to probe their effect on lysozyme activity and the molecular interaction in aqueous solutions. Specifically, the effects of pH and concentration of ILs on lysozyme activity were investigated by using the spectrophotometric turbidity assay. The results demonstrated that the effect of ILs on lysozyme activity depended on the concentration of ILs. Fixing the pH at 6.85, lysozyme activity rose firstly and then reduced with the increase of concentration of four ILs, reaching the maximum at 75 mM. The UV–Vis spectra illustrated that the interaction between ILs and lysozyme was weak. The results of emission and synchronous fluorescence spectra indicated that ILs had a quenching effect on the fluorescence of lysozyme, and the quenching effect increased with the increasing concentration of ILs. Meanwhile, the fluorescent quenching mechanism of ILs on lysozyme was dynamic quenching, and ILs had significant effects on the tryptophan (Trp) residues Trp62 or Trp108 at the active site of lysozyme, which suggested that effects of ILs on lysozyme activity could be attributed to the conformational changes of lysozyme triggered by changes in the microenvironment surrounding Trp62 or Trp108.

Sorption of Pb(II) onto biochar is enhanced through co-sorption of dissolved organic matter

Biochar plays an important role in controlling migration of pollutants in soils. However, little information is available on the interactions between soil-derived dissolved organic matter (DOM), biochar and soluble metal species. The aim of this work was to present the adsorption process of soil DOM by biochar (corn straw biochar produced at 700 °C) and to determine whether co-sorption of DOM would change the affinity for Pb(II). The adsorption rates of biochar and biochar + DOM for Pb(II) were best fitted with a pseudo-second order kinetic model, and the equilibrium adsorption isotherm data agreed well with both the Langmuir and Freundlich models. Adsorption of DOM to biochar reached equilibrium after 15 h with an uptake of 52% of the supplied DOM. We used fluorescence excitation-emission matrices (EEMs) with parallel factor (PARAFAC) analysis to demonstrate that protein-like, fulvic acid-like and humic acid-like substances were the primary constituents of the DOM, which were quenched over time in the presence of biochar. Synchronous fluorescence spectra indicated that the protein-like structures were the predominant fluorescence substances in DOM. Two-dimensional correlation spectroscopy (2D-COS) showed the binding of DOM to biochar resulted in the quenching of fluorescence in the order: protein-like substances > humic-like substances (280 > 355 nm). Data supports the notion that DOM can increase the adsorption capacity of biochar for metal-ions.

Multispectroscopic and synergistic antioxidant study on the combined binding of caffeic acid and (-)-epicatechin gallate to lysozyme

The binding of caffeic acid (CA) and/or (-)-epicatechin gallate (ECG) to lysozyme was investigated by multispectroscopic methods and molecular docking. The effects of the single and combined binding on the structure, activity and stability of lysozyme and the synergistic antioxidant activity of CA and ECG were also studied. Fluorescence quenching spectra, time-resolved fluorescence spectra, and UV–vis absorption difference spectra all ascertained the static quenching mechanism of lysozyme by CA/ECG. Thermodynamic parameters indicated that CA and ECG competitively bound to lysozyme, and CA had a stronger binding affinity, which was consistent with the results of molecular docking. Hydrogen bonding, van der Waals’ force and electrostatic interaction were the main driving forces for the binding process. Synchronous fluorescence spectra displayed that the interaction of CA/ECG exposed the tryptophan residues of lysozyme to a more hydrophilic environment. Circular dichroism spectroscopy, Fourier transform infrared spectroscopy and dynamic light scattering indicated that the binding of CA and/or ECG to lysozyme resulted in the change of the secondary structure and increased the particle size of lysozyme. The binding of CA and/or ECG to lysozyme inhibited the enzyme activity and enhanced the thermal stability of lysozyme. The combined application of CA and ECG showed antioxidant synergy which was influenced by the encapsulation of lysozyme and cellular uptake. In summary, this work provides theoretical guidance for lysozyme as a carrier for the combined application of CA and ECG.

Multi-spectroscopic investigation of the molecular weight distribution and copper binding ability of dissolved organic matter in Dongping Lake, China

The properties and metal-binding abilities of dissolved organic matter (DOM) rely on its molecular weight (MW) structure. In this study, the spatial differences of DOM in compositions, MW structures, and binding mechanisms with copper (Cu2+) in Dongping Lake were investigated by applying excitation-emission matrix combining parallel factor analysis (EEM-PARAFAC), synchronous fluorescence (SF) spectra, two-dimensional correlation spectra (2D-COS), and Fourier transform infrared (FTIR) spectra. The EDOM for the entrance of the Dawen River and PDOM for the macrophyte-dominated region were divided from DOM of Dongping Lake based on hierarchical clustering analysis (HCA) and principal component analysis (PCA) and were size-fractioned into MW < 500 kDa and <100 kDa fractions. According to EEM-PARAFAC, Dongping Lake was dominated by tryptophan-like substances with MW < 500 kDa. The concentration of PDOM was higher than that of EDOM (p < 0.05). 2D-COS showed that protein-like components preceded humic-like components binding to Cu2+ regardless of sample type (215 nm > 285 nm > 310–360 nm). The Cu2+ binding capacity of DOM exhibited specific differences in space, components, and molecular weights. The humic-like component 1 (C1) and tryptophan-like component 4 (C4) of PDOM showed stronger binding abilities than those of EDOM. Endogenous tryptophan-like component 4 (C4) had a higher binding affinity for Cu2+ than humic-like components (logKa: C4 > C1 > C2) in PDOM irrespective of MW. Humic-like components with MW < 500 kDa displayed higher binding potentials for Cu2+. FTIR spectra showed that the main participants of DOM-Cu complexation included aromatic hydrocarbons, aliphatic groups, amide Ⅰ bands, and carboxyl functional groups. This study provides spatial-scale insights into the molecular weight structure of DOM in influencing the behavior, fate, and bioavailability of heavy metals in lakes.

Solar irradiation-induced photochemical processing of dissolved organic matter in reclaimed water

The photochemical fate of various organic components of reclaimed water DOM was comprehensively investigated using diverse spectroscopic characterization coupled with mathematical analysis methods. Findings show reclaimed water DOM to be susceptible to solar irradiation-induced photodegradation, causing notable reduction of UV254 absorbance, fluorescence intensity, and average molecular weight of DOM in reclaimed water. A multiple exponential kinetic model for DOM photodegradation demonstrates humic-like constituents were more susceptive to solar irradiation, whereas the protein-like constituents showed tolerance. FRI analysis show photodegradation rate constants of DOM factions under sunlight irradiation fall in the sequence of humic-like > fulvic-like > soluble microbial byproduct-like > tryptophan-like > tyrosine-like fractions. Upon solar irradiation, the photodegradation kinetics of three PARAFAC-extracted fluorophores varied in the order of microbial humic-like > terrestrial humic-like > tryptophan-like components. This order of fraction decrease is further evidenced by synchronous fluorescence spectra (SFS) integrated with 2DCOS analysis. Different photoreactivities and photosensitivity to visible (Vis), Vis + UVA, Vis + UVA + UVB by PARAFAC-derived components demonstrated that UV irradiation, but not visible light, drive DOM photodegradation. UVB and UVA played predominant roles in the photodegradation of tryptophan-like and terrestrial humic-like constituents, respectively. The photodegradation of microbial humic-like constituents was attributed to the combined actions of UVB and UVA irradiation. Furthermore, varied ROS quenching/enhancing experiments revealed that the photodegradation of tryptophan-like components might be ascribed to indirect photolysis involving 3DOM*. The photodegradation of terrestrial/microbial humic-like DOM constituents was associated with direct photolysis. The comprehensive illustration of sunlight irradiation-induced photochemical transformation of DOM in reclaimed water during storage contributes to understanding the fate of DOM and associated environmental processes impacted by solar irradiation.

Assessment of lipophilic fluorescence products in β-amyloid-induced cognitive decline: A parallel track in hippocampus, CSF, plasma and erythrocytes.

Oxidative stress implicates in Alzheimer's disease (AD) pathophysiology, and associates with the creation of end products of free radical reactions, are known as lipophilic fluorescent products (LFPs). This study aimed to evaluate the probable parallel alterations in the spectral properties of the LFPs in the hippocampus tissues, cerebrospinal fluid (CSF), plasma, and erythrocytes during AD model induction by intra-cerebroventricular (ICV) amyloid β-protein fragment 25-35 (Aβ) injection. Male rats received an intra-ICV injection of Aβ. Hippocampus, CSF, plasma, and erythrocytes were harvested at 5, 14, and 21days after Aβ injection. The fluorescent intensity of LFPs was assessed by spectrofluorimetry using synchronous fluorescence spectra 25 (SYN 25) and 50 (SYN 50) in the range of 250-500nm. Hippocampal tissue malondialdehyde (MDA) and superoxide dismutase (SOD) were also measured. Cognitive alterations were evaluated using Morris water maze (MWM) test. The parallel significant rise in the fluorescence intensity of LFPs was detected in the hippocampus, CSF, plasma, and erythrocytes, 14, and 21days after ICV-Aβ injection. These alterations were found in both types of synchronous spectra 25, and 50, and were coincided with hippocampal cognitive decline, the MDA rise, and decrease of SOD activity. There was a positive correlation between hippocampus homogenate, and plasma or CSF rise in fluorescence intensity. Data showed that the Aβ increased hippocampal MDA, and decreased SOD activity, led to a higher rate of oxidative products and subsequently resulted in an increase in LFPs fluorescence intensity during the development of cognitive decline. LFPs' alterations reflect a comprehensive view of tissue redox status. The fluorescence properties of LFPs indicate their composition, which may pave the way to trace the different pathological states.

Rapid quantification of acid value in frying oil using iron tetraphenylporphyrin fluorescent sensor coupled with density functional theory and multivariate analysis

Abstract A metalloporphyrin-based fluorescent sensor was developed to determine the acid value in frying oil. The electronic and structural performances of iron tetraphenylporphyrin (FeTPP) were theoretically investigated using time-dependent density functional theory and density functional theory at the B3LYP/LANL2DZ level. The quantified FeTPP-based fluorescent sensor results revealed its excellent performance in discriminating different analytes. In the present work, the acid value of palm olein was determined after every single frying cycle. A total of 10 frying cycles were conducted each day for 10 consecutive days. The FeTPP-based fluorescent sensor was used to quantify the acid value, and the results were compared with the chemical data obtained by conventional titration method. The synchronous fluorescence spectrum for each sample was recorded. Parallel factor analysis was used to decompose the three-dimensional spectrum data. Then, the support vector regression (SVR), partial least squares, and back-propagation artificial neural network methods were applied to build the regression models. After the comparison of the constructed models, the SVR models exhibited the highest correlation coefficients among all models, with 0.9748 and 0.9276 for the training and test sets, respectively. The findings suggested the potential of FeTPP-based fluorescent sensor in rapid monitoring of frying oil quality and perhaps also in other foods with higher oil contents.

Surfactant flooding for enhanced oil recovery – Insights on oil solubilization through optical spectroscopic approach

Surfactant flooding is a proven method employed to improve the recovery of crude oil from subsurface reservoirs but the knowledge about microemulsion formation, factors related to their stability, and the trapping mechanism of crude oil components in a microemulsion is still not clear for designing of injection fluid for specific crude type. The interaction mechanisms of four crude oils with surfactant-brine solutions were studied in this work for better insight into the molecular level mechanisms during surfactant flooding. UV–visible absorption and fluorescence spectra of the separated maltene and asphaltene fractions indicate the structural difference of the components in the molecular level, particularly, the size of the fused aromatic rings (FAR) present within individual bulk crude sample. Moreover, the FTIR spectra of the separated asphaltenes from the crude samples clearly showed the subtle difference in the functional groups present in respective FAR structures. Well-characterized compositionally different crude oils were mixed with four different surfactant-brine solutions (anionic – SDS, AOS, cationic - CTAB, and neutral - TX-100) and examined using UV–visible absorption and fluorescence spectroscopic approach. Detailed analysis of the acquired absorption and fluorescence spectra of the crude oil-surfactant-brine solutions distinctly demonstrate the entrapment of different crude oil components within the micelles formed by surfactants of different charges while the synchronous fluorescence spectra show the entrapment of specific size FARs within the specific micellar microenvironment. The results exhibit that the anionic surfactant entraps the smaller size (2–4) FARs whereas cationic and neutral surfactants entrap small as well as medium size (2–6) FARs within the formed micelles in the microemulsions. The present spectroscopic study signifies the importance of molecular-level interaction mechanisms for customized designing of surfactant solutions for maximizing crude oil recovery from petroleum reservoirs.

Synchronous fluorescence spectroscopy and multivariate classification for the discrimination of cachaças and rums

Although cachaça and rum are distilled beverages obtained from the same raw material, they present differences in their chemical compositions. In this study, synchronous fluorescence spectroscopy was used combined with supervised classification models based on the partial least squares discriminant analysis to develop a rapid and low-cost model for discriminating between 50 cachaça and 40 rum samples. Partial least squares discriminant analysis models were constructed using synchronous fluorescence spectra recorded at wavelength differences of 10–100 nm. Initially, spectra were preprocessed by the first derivative with the Savitzky-Golay smoothing, and filter width and polynomial order were selected through face-centered central composite designs. For the construction and validation models, the spectra data were split into two datasets: the training and the test sets containing 60 (C, n = 33; R, n = 27) and 30 (C, n = 17; R, n = 13) samples, respectively. The best discrimination was achieved using fluorescence spectra recorded at wavelength difference 10 nm, allowing the discrimination of cachaça and rum with a classification efficiency of 98%. These results indicate that synchronous fluorescence spectroscopy offers a promising approach for the authentication of cachaças and rums.