Measurements Of Fluorescence Spectra Research Articles

Localization and dynamics of the anticarcinogenic curcumin with GM1 and other miceller assemblies.

Structural transitions involving shape changes play an important role in cellular physiology and enhance the bioavailability of the natural food like curcumin in surfactant aggregates. In this work, we have studied the localization, dynamics and stability of curcumin in various miceller assemblies using a combination of absorbance and fluorescence spectroscopic approaches. The measurements of absorption and fluorescence spectra of curcumin revealed that the nature of interactions of ionic and nonionic surfactants and the glycosphingolipid, GM1 with curcumin is significantly different with surfactant concentrations. At low concentrations of SDS and the GM1 the head group of SDS and GM1 binds to the central β-diketone group of curcumin to form SDS-curcumin or GM1-curcumin complexes. At high concentrations, both formed micelles with curcumin completely solubilized inside. Cucurmin is solubilized in the stern layer of SDS micelles. Compared to spherical micelles, rod shaped micelles allow more curcumin to bind through hydrophobic interactions indicated by higher absorption and fluorescence, enhanced partition coefficient and stability. Whereas curcumin associates with GM1 micelles with lower partition coefficient, solubility and remain closer to aqueous phase decreasing its bioavailability and stability. While cucurmin is solubilized in the palisade layer of deoxycholate and octyl glucopyranoside micelles through the alkyl chains providing more hydrophobic microenvironment to curcumin with enhanced stability and bioavailability. Graphical abstract Schematic diagram of the two different types of detergent micelles and larger GM1 micelles.

Effect of malondialdehyde on the ovalbumin structure and its interactions with T84 epithelial cells

BackgroundProtein oxidation can occur as a consequence of lipid peroxidation during food processing. The aim of this work was to explore the effect of malondialdehyde (MDA) modification of ovalbumin (OVA) on its interaction with T84 intestinal cells. MethodsMolecular dynamics simulation was employed for the prediction of MDA modification in the OVA, while introduced structural changes were evaluated by measurement of carbonyl group content, fluorescence spectra, MS/MS analysis, and IgE reactivity. Effects of MDA modified OVA on T84 epithelial cells were analyzed by gene expression for pro-inflammatory cytokines and protein secretion. ResultsOut of 9 predicted, five modified Lys residues were confirmed by MS/MS analysis: 51TQINKVVR58, 85DILNQITKPNDVYSFSLASR104, 111YPILPEYLQCVKELYR126, 187AFKDEDTQAMPFR199, 277KIKVYLPR284, and 278IKVYLPR284. The introduced MDA modifications influenced profile of IgE reactivity to OVA. Treatment of T84 epithelial cells with OVA and OVA modified with 1mM MDA, induced up-regulation of pro-inflammatory cytokines (IL-1β, IL-25, IL-33, TSLP and TNFα), while OVA modification with 10mM MDA induced down regulation of the cytokine expression profile, except for IL-1β. OVA and OVA modified with 1mM MDA induced secretion of epithelial cells specific cytokine IL-33. ConclusionsThis finding indicated that OVA and its MDA modified form have the potential to trigger the innate immunity by inducing up-regulation and secretion of pro-allergenic IL-33 in T84 intestinal epithelial cells. General significanceInteractions of ovalbumin and its MDA modified form with intestinal epithelial cells can induce a specific immunological priming necessary for the downstream activation of innate immunity.

Characterization of DOM adsorption of CNTs by using excitation–emission matrix fluorescence spectroscopy and multiway analysis

ABSTRACTCarbon nanotubes (CNTs) were utilized to adsorb DOM in micro-polluted water. The characteristics of DOM adsorption on CNTs were investigated based on UV254, TOC, and fluorescence spectrum measurements. Based on PARAFAC (parallel factor) analysis, four fluorescent components were extracted, including one protein-like component (C4) and three humic acid-like components (C1, C2, and C3). The adsorption isotherms, kinetics, and thermodynamics of DOM adsorption on CNTs were further investigated. A Freundlich isotherm model fit the adsorption data well with high values of correlation. As a type of macro-porous and meso-porous adsorbent, CNTs preferably adsorb humic acid-like substances rather than protein-like substances. The increasing temperature will speed up the adsorption process. The self-organizing map (SOM) analysis further explains the fluorescent properties of water samples. The results provide a new insight into the adsorption behaviour of DOM fluorescent components on CNTs.

Rapid ultrasensitive chemometrics-fluorescence methodology to quantify fluoroquinolones antibiotics residues in surface water

A sensitive method for the determination of fluoroquinolones in surface waters at trace concentration level is presented. The proposed two-step methodology consists in a solid-phase extraction using C-18 membranes followed measurement of the emission molecular fluorescence spectra over extracted membrane without elution of the analytes. Membrane background signal was removed by the used of chemometrics calculations, in addition chemometrics was as well used for the direct and simultaneous determination of the studied compounds. The method was optimized for the analysis of three fluoroquinolones: enoxacin (ENO), norfloxacin (NOR) and ofloxacin (OFLO). The fluorescence of these compounds increase drastically when they are in the membrane, thus with this method low concentrations are possible to be determined, as the concentration in which these compounds appear in surface water. Limits of detection at the ng•L–1 level were estimated for ENO, NOR and OFLO.

LED-induced fluorescence spectroscopy technique for apple freshness and quality detection

The LED-induced fluorescence spectroscopy technique is developed to detect apple freshness and quality. A compact and automatic system is set up for fast measurements of apple fluorescence spectra. The partial least square regression (PLSR) method is used to establish a predictive model between fluorescence signals and corresponding actual apple qualities. Apple freshness is related to physiological aging, and apple quality is expressed by firmness (F) and soluble solids content (SSC). As for freshness detection, an LED at 375nm is demonstrated to be more effective than at 400nm with a root mean square error of validation (RMSEV) of 4.73d. Meanwhile, the prediction results of the firmness and SSC for two kinds of apples also show low RMSEV values of 6.88N and 0.98%, respectively, indicating that the LED-induced fluorescence spectroscopy technique is an effective, convenient and promising method for scanning apples and perhaps other foods.

New ESIPT-Inspired Photostabilizers of Two-Photon Absorption Coumarin–Benzotriazole Dyads: From Experiments to Molecular Modeling

In this work, a variety of new coumarin–benzotriazole dyads are synthesized to study the photostabilities under the irradiation of broad UV light as well as near-infrared (near-IR) laser respectively inspired by efficient excited state intramolecular proton transfer (ESIPT). The corresponding esterified dyads and the coumarin dyes are prepared as the references. The intramolecular hydrogen bond in the target dyads is confirmed by 1H NMR spectra and UV/visible absorption spectra. The internal proton transfer in the excited states of the target dyads under single photon excitation and near-IR laser irradiation is demonstrated by the measurements of one-photon fluorescence spectra and two-photon upconverted fluorescence spectra, respectively. The photostabilities of the target dyads under broad UV light irradiation and near-IR laser irradiation in various organic solvents with saturated air, oxygen, or argon are studied. The theoretical evidence of ESIPT of the target dyads is provided by the molecular geome...

Bistable random laser that uses a phase transition of polyethylene glycol

Polyethylene glycol (PEG) is transparent in the liquid phase and turns to a translucent solid through a phase transition at around room temperature. A PEG solution of rhodamine 6G was excited by a laser pulse (527 nm wavelength, 10 ns duration, 190 μJ) to measure fluorescence spectra during the phase transition process. Whereas the fluorescence peak was weak and broad at 60 °C (spontaneous emission), a strong, narrow peak appeared in the temperature range below 50 °C, since a stimulated emission (amplified spontaneous emission) took place due to the scattering in the solid PEG. This laser emission control was repeatable by reversing an electric voltage (−12 or +12 V) that drove a Peltier element. Interestingly, the sample exhibited a strong stimulated emission at 52 °C during the heating process, although no strong emission was visible at the same temperature during the cooling process (bistability). The fluorescence peak wavelength was tunable between 566 and 572 nm by changing the cooling rate.

SUPR: Spectral Unmixinig Plate Reader for Live-Cell FRET Biosensor Drug Screening

We have developed a high-throughput Spectral Unmixing Plate Reader (SUPR) which can acquire a fluorescence emission spectrum across 384 wells, with short (< 4 min) read time for the entire plate. The entire spectrum is recorded at once with a compact spectrometer equipped with an uncooled one-dimensional array detector. For application to FRET in living cells, FRET protein biosensors, with genetically encoded GFP (donor) and RFP (acceptor) tags, are expressed in HEK cells, and single-component spectra are acquired from water (Raman), untransfected cells (autofluorescence), cells expressing donor only, and cells expressing acceptor only. Each observed spectrum is decomposed into a linear combination of component spectra to determine FRET efficiency. The method enables unprecedented speed, precision, and accuracy. It rigorously and painlessly accounts for phenomena such as bleed-through of the donor emission into the acceptor channel, cross-talk associated with direct excitation of the acceptor, and cell autofluorescence. Excitation and detection are both from the top, so low-cost polypropylene plates typically used in qPCR work very well in this application. This novel technology has been combined with our previously developed fluorescence lifetime technology (Petersen et al, Rev Sci Inst, 2014) allowing for high-throughput quantitation of FRET efficiency from independent measurements. We have screened small-molecule libraries with an intramolecular cardiac calcium pump FRET biosensor, expressed in living cells (Gruber et al., J. Biomol Screening, 2014) using this multiplexed fluorescence detection platform and identified several previously unknown small-molecule effectors. The information obtained from both fluorescence lifetime and spectrum measurements reduced the number of false-positives and increased confidence in our hit selection methods. The development of this technology and screening assay will prove useful for drug discovery but also answering basic biological questions with fluorescence based assays.

Precise Fractionation of CdSe/ZnS Quantum Dot-Organic-Dye Conjugates Using a Gel Filtration Column.

Conjugates of semiconductor quantum dots (QDs) and organic dyes have been receiving attention as fluorescence biological sensing materials. In designing such sensors, a most important parameter is the number of organic-dye molecules that conjugate to a QD. If a precise separation method was developed, it might be possible to control conjugation without knowing the exact number of conjugated dye molecules per QD. In this study, the difference in linear velocities in a gel filtration column between CdSe/ZnS QDs and 5-(and 6)-carboxynaphthofluorescein succinimidyl ester is used. The velocities differ because the hydrophilicity of CdSe/ZnS QDs is much higher than that of the organic dye; hence, CdSe/ZnS-organic-dye conjugation can be controlled by changing the fraction number. Furthermore, the concentrations of CdSe/ZnS QDs and organic dye in fractionated solutions can be determined by measuring fluorescence spectra, and we demonstrate a fluorescence-type pH sensor based on the conjugate, which has a pH-sensitivity range from 7.5 - 9.5.

Accurate identification of nitrogen fertilizer application of paddy rice using laser-induced fluorescence combined with support vector machine

To identify accurately the doses of nitrogen (N) fertilizer and improve the photosynthetic efficiency of paddy rice, laser induced fluorescence (LIF) technique combined with the support vector machine (SVM) and principal component analysis (PCA) is proposed in this paper. The LIF technology, in which the ultraviolet light (355 nm) is applied as an excitation light source, is employed to measure fluorescence spectra of paddy rice. These fluorescence spectra demonstrate that the fluorescence spectral characteristics of paddy rice leaves with different doses of N fertilizer have distinct differences from each other. Then, PCA and SVM are implemented to extract the features of fluorescence spectra and to recognize different doses of N fertilizer, respectively. The overall recognition accuracy can reach 95%. The results show that the LIF technology combined with PCA and SVM is a convenient, rapid, and sensitive diagnostic method for detecting N levels of paddy rice. Thus, it will also be convenient for farmers to manage accurately their fertilization strategies.

Luminescence properties of alkali metal ions sensitized CaFCl:Tb3+ nanophosphors

A series of CaFCl:Tb3+ and CaFCl:Tb3+,A+ (A=Li, Na and K) nanophosphors were synthesized by the one-step sol-gel method, which were reported for the first time. The sample consisted of monodisperse particles, the average size of which was 37 nm. The emissions of Tb3+ ions and oxygen defects OF? were demonstrated in the CaFCl:Tb3+ samples. The former was made up of several peaks at 488, 545, 587 and 623 nm, ascribed to 5D4→7FJ (J=6−3) transitions of Tb3+ ions. The latter was shown as a broad band peaked at about 450 nm. Alkali metal ions A+ (A=Li, Na and K) were introduced as the charge compensators to improve the luminescence of samples. The influence of charge compensators on the emissions of Tb3+ ions and oxygen defects OF? was investigated by the measurement of fluorescence spectra and luminescence decay curves. The results indicated that all the charge compensators weakened the defects emission. Furthermore, Li+ ion was the best charge compensator, because it not only reduced the defects emission but also increased the emission intensity of Tb3+ significantly. Our results suggested that this nanophosphor sensitized by the charge compensator might broaden potential applications of rare-earth doped CaFCl.

Steady-State Fluorescence and Lifetime Emission Study of pH-Sensitive Probes Based on i-motif Forming Oligonucleotides Single and Double Labeled with Pyrene

Cytosine-rich nucleic acids undergo pH-stimulated structural transitions leading to formation of an i-motif architecture at an acidic pH. Thus, i-motifs are good foundation for designing simple pH-sensitive fluorescent probes. We report here steady-state and time-resolved fluorescence studies of pyrene-labeled probes based on RET sequence: C4GC4GC4GC4TA (RET21), AC4GC4GC4GC4TA (RET21A) and C4GC4GC4GC4T (RET20). Comparative studies with single- and double-labeled i-motif probes were carried out. For each probe, we have measured fluorescence spectra and decays for emission wavelength of 390 nm over a wide range of pH (from 4.0 to 8.0). Effect of the oligonucleotide sequence and the number of pyrene labels on the spectral characteristics of probes were discussed.

Enhanced brightness of 2,6-diphenylthiazolo[4,5-b]pyrazines by introducing double electron donating groups

Abstract Thiazolo[4,5-b]pyrazine (TPy) derivatives with enhanced fluorescence brightness were developed by tuning the double substituents. The spectroscopic and photophysical properties were investigated by measurements of absorption and fluorescence spectra, fluorescence yields and lifetimes. Based on the DFT calculations, the increased brightness was rationalized by the enhanced electronic absorptivity and fluorescence yields. The developed methodology provides the guide to design high-performance TPy fluorophores.

Determination of polycyclic aromatic hydrocarbons by four-way parallel factor analysis in presence of humic acid

There is not effective method to solve the quenching effect of quencher in fluorescence spectra measurement and recognition of polycyclic aromatic hydrocarbons in aquatic environment. In this work, a four-way dataset combined with four-way parallel factor analysis is used to identify and quantify polycyclic aromatic hydrocarbons in the presence of humic acid, a fluorescent quencher and an ubiquitous substance in aquatic system, through modeling the quenching effect of humic acid by decomposing the four-way dataset into four loading matrices corresponding to relative concentration, excitation spectra, emission spectra and fluorescence quantum yield, respectively. It is found that Phenanthrene, pyrene, anthracene and fluorene can be recognized simultaneously with the similarities all above 0.980 between resolved spectra and reference spectra. Moreover, the concentrations of them ranging from 0 to 8μgL−1 in the test samples prepared with river water could also be predicted successfully with recovery rate of each polycyclic aromatic hydrocarbon between 100% and 120%, which were higher than those of three-way PARAFAC. These results demonstrate that the combination of four-way dataset with four-way parallel factor analysis could be a promising method to recognize the fluorescence spectra of polycyclic aromatic hydrocarbons in the presence of fluorescent quencher from both qualitative and quantitative perspective.

Measurements of reflectance and fluorescence spectra for nondestructive characterizing ripeness of grapevine berries

In vivo reflectance and fluorescence spectra from berry skins of a white (Riesling) and red (Cabernet Sauvignon) grapevine variety were measured during a ripening season with a new CMOS radiometer instrument. Classical reference measurements were also carried out for a sugar content of the berry juice [°Brix] and pigment contents (chlorophyll a and b, carotenoids, anthocyanins) from methanol extracts of the berry skin. We showed that the colours and the spectra analysed from them could be taken as an unambiguous indicator of grapevine ripening. Reflectance spectra, which were affected by the content of pigments (chlorophylls and anthocyanins), effects of surface (wax layers), and tissue structure (cell size) of the berries well correlated (R 2 = 0.89) with the °Brix measurements of the berries. The fast data acquisition of both reflectance and fluorescence spectra in one sample with our radiometer instrument made it superior over the time-consuming, traditional, and mostly destructive chemical analysis used in vine-growing management.

Spectroscopic and laser properties of Cr2+ ions in Zn1−xMgxSe solid solutions

Investigations of spectroscopic and laser properties of Cr2+ ions in Zn1−xMgxSe solid solutions with different Zn–Mg ratio described by the Mg content x ranging from 0 to 0.3 are carried out. The absorption and fluorescence spectra of Cr2+ ions shift towards longer wavelengths with the increasing x is presented. Fluorescence spectra and lifetime for the 80–300K temperature range are shown. Lasing properties are demonstrated and the laser output wavelength red shift with the increasing magnesium content x is in a good agreement with the measured fluorescence spectra.

Strong positive cooperativity in binding to the A3T3 repeat by Hoechst 33258 derivatives attaching the quinoline units at the end of a branched linker

Hoechst 33258 derivatives with additional interacting moieties attached at the ends of branched linkers were synthesized, and their DNA binding properties were investigated with regard to the A3T3 repeat by measuring fluorescence spectra. The binding property of the ligand was investigated by fluorescence titration, and the titration data were analyzed using the McGhee–von Hippel method. Ligand 6Q with the quinolin-6-yloxyacetyl group and Ligand IQ with isoquinolin-6-yloxyacetyl group at the ends of the branched linkers exhibit highly positive cooperativity for the DNA having 5 A3T3 sites with 3 base-insertions between them with sequence selectivity. The strategy developed in this study may be generally applicable for designing ligands for repetitive DNA sequences.

Fluorescence spectroscopy and chemometric modeling for bioprocess monitoring.

On-line sensors for the detection of crucial process parameters are desirable for the monitoring, control and automation of processes in the biotechnology, food and pharma industry. Fluorescence spectroscopy as a highly developed and non-invasive technique that enables the on-line measurements of substrate and product concentrations or the identification of characteristic process states. During a cultivation process significant changes occur in the fluorescence spectra. By means of chemometric modeling, prediction models can be calculated and applied for process supervision and control to provide increased quality and the productivity of bioprocesses. A range of applications for different microorganisms and analytes has been proposed during the last years. This contribution provides an overview of different analysis methods for the measured fluorescence spectra and the model-building chemometric methods used for various microbial cultivations. Most of these processes are observed using the BioView® Sensor, thanks to its robustness and insensitivity to adverse process conditions. Beyond that, the PLS-method is the most frequently used chemometric method for the calculation of process models and prediction of process variables.

Broadband 2 μm fluorescence and energy transfer evaluation in Ho3+/Er3+ codoped germanosilicate glass

This work reports the broadband 2μm emission from Ho3+/Er3+ codoped germanosilicate glasses. Spectral components of the 2μm emission band were analyzed and an equivalent model of four-level system was proposed to describe the 2μm emission band. The results suggested that Ho3+/Er3+ codoped germanosilicate glass has high effective emission bandwidth (172nm), large emission cross section (5.18×10−21cm2) and gain bandwidth (891×10−28cm3), which is a promising candidate for 2μm laser and amplifier. In addition, energy transfer mechanism between Ho3+ and Er3+ ions was investigated based on the measured fluorescence spectra and decay curves of Er3+:4I11/2 and 4I13/2 levels. Energy transfer efficiency and microscopic parameters were calculated to evaluate the 2μm fluorescence. Moreover, a rate equation model between Ho3+ and Er3+ ions was developed to elucidate 2μm fluorescence behaviors. This work might provide useful guide to investigate fluorescence behavior and energy transfer mechanism of rare earth ions.

Photoexcited triplet states of UV-B absorbers: ethylhexyl triazone and diethylhexylbutamido triazone.

The excited states of UV-B absorbers, ethylhexyl triazone (EHT) and diethylhexylbutamido triazone (DBT), have been studied through measurements of UV absorption, fluorescence, phosphorescence, triplet-triplet absorption and electron paramagnetic resonance spectra in ethanol. The energy levels of the lowest excited singlet (S1) and triplet (T1) states and quantum yields of fluorescence and phosphorescence of EHT and DBT were determined. In ethanol at 77 K, the deactivation process of EHT and DBT is predominantly fluorescence, however, a significant portion of the S1 molecules undergoes intersystem crossing to the T1 state. The observed phosphorescence spectra, T1 lifetimes and zero-field splitting parameters suggest that the T1 state of EHT can be assigned to a locally excited (3)ππ* state within p-(N-methylamino)benzoic acid, while the T1 state of DBT can be assigned to a locally excited (3)ππ* state within p-(N-methylamino)benzoic acid or p-amino-N-methylbenzamide. The quantum yields of singlet oxygen generation by EHT and DBT were determined by time-resolved near-IR phosphorescence measurements in ethanol at room temperature. EHT and DBT did not exhibit significantly antioxidative properties by quenching singlet oxygen, in contrast to the study by Lhiaubet-Vallet et al.