Excitationand Emission Research Articles

Design, synthesis, and thermal stability of rare earth luminescent materials

As a new generation of luminescent materials, aluminate rare earth materials have the characteristics of long luminescent time, adjustable wavelength and high brightness. Aluminate rare earth luminescent materials were prepared by high temperature solid-state method, and the luminescent properties of the luminescent materials were studied. Firstly, the author synthesized magnesium aluminate, calcium aluminates, and zinc aluminate matrix by combustion method. Then aluminate rare earth luminescent materials were prepared by high temperature solid phase method through raw material distribution, raw material mixing, drying, calcination, and post-treatment. Finally, a fluorescence spectrophotometer was used to measure the excitation and emission spectra of the prepared sample material. The research results indicate that the excitation wavelength does not affect the relationship between the emission wavelength and light intensity, the emission spectra of MgAl2O4:Tb3+ and CaAl2O4:Tb3+ exhibit narrowband transition emission states; When the mass fraction of rare earth factor Eu3+ in the activator is 6% and the temperature is 1300?C, the emission peak intensity of the luminescent material reaches its maximum value, and the luminescence intensity is the best.

Multivariate spectrofluorimetric detection of lipase isolated from Serratia marcescens in chromatographic fractions.

Lipases are ubiquitous enzymes and widespread in nature. They have been widely purified as one of the most important enzymes in molecular biosciences and biotechnology. In this paper, the extracellular lipase was separated from Serratia marcescens. The separated enzyme was purified partially by ammonium sulfate precipitation, dialysis and gel filtration chromatography. Presence of the lipase in chromatography fractions was assayed by the hydrolysis of paranitrophenyl palmitate (pNPP) as substrate. The excitation and emission (EEM) fluorescence spectra of purified lipase in chromatographic fractions were investigated. The study demonstrates an application of fluorescence spectroscopy, combined with multivariate regression methods, to the analysis of fluorescent lipase component. N-way partial least squares (N-PLS) was utilized to show the importance of region selection in calibration modeling of the data. Genetic algorithm (GA) optimization was applied to improve the performance of radial basis function network based regression model. RBF-ANN was used to calibrate and predict lipase activity. The analytical performance of RBF-ANN method was characterized by Q^2parameter. The value of Q^2 was 0.919. The proposed method was successfully applied to the analysis of protein containing fractions and in order to explore the three way fluorescence data array from separated fractions, parallel factor analysis (PARAFAC) was applied. The fluorescence signal was resolved into excitation and emission profiles of the pure fluorescent compounds.

Validated Microemulsion Liquid Chromatography-Fluorescence Method for the Quantification of Duloxetine and its Two Main Metabolites in Plasma: Application to Clinical Pharmacokinetic Studies

Background: Duloxetine (DL) is a selective serotonin and norepinephrine reuptake inhibitor. The drug is used in the treatment of major depression, anxiety, pain related to diabetic peripheral neuropathy and stress urinary incontinence. </P><P> Objective: This study described, for the first time, the development and validation of a highly selective and sensitive microemulsion liquid chromatography-fluorescence (MELC-FL) method with low environmental pollution and without extraction steps for the simultaneous quantification of DL, and its two main metabolites; 5-hydroxy-6-methoxy duloxetine (5-HDL) and 4-hydroxy duloxetine glucuronide (4- HDLG) in plasma. Methods: The studied analytes and methyl paraben (an internal standard) were detected using excitation and emission wavelengths of 280 and 340 nm, respectively. The analysis was performed on Water Symmetry C18 analytical column (100 Å, 150 mm x 3.9 mm, 5 µm) by directly injecting the plasma after appropriate dilution with microemulsion mobile phase. Total analytical run time was 4 min. Results: The MELC-FL method was statistically validated according to the FDA guidelines for bioanalytical methods for linearity, accuracy, precision, specificity, robustness, and stability. Linear calibration plots were achieved in the ranges of 25-1200 ng/mL for DL and 50-1500 ng/mL for 5-HDL and 4- HDLG (r2 ≥ 0.997) in rat plasma. The intra- and inter- assay precisions and accuracy were acceptable. The overall recoveries of DL and its two main metabolites from rat plasma were between 97.12% and 103.12% with an RSD value between 0.34% and 4.57%. Conclusion: The present study supports the possible use of the microemulsion mobile phase in LC as a “greener ” mobile phase. The developed method offered an advantage in the form of direct analysis of biological samples after appropriate dilution with eco-friendly microemulsion mobile phase, which decreased the possibility of sample loss during analysis. The developed assay was successfully applied in a pharmacokinetic study and it established the applicability of the method for the determination of concentration-time profiles of DL and its two main metabolites in rat plasma after systemic administration.

Spectrometric Characteristic of Superficial <i>Chlorella</i> Sp. Grown in Photo-Bioreactor under Different Flow Rates

In this study, photo-bioreactor designed with 4 L of volume to cultivate Chlorella sp. was conducted for comparing the differences of biomass increase among three gas flow rates. All experiments were controlled at light reaction of 12 hrs. with 1,700 lux. The organic fluorescence of algae, expressed in excitation emission fluorescent matrix (EEFM), was obtained from algal solution deducted from EEFM of the filtrate obtained from the filtration of algal solution using 0.2 μm membrane filter. Also, the surface charge and functional group for Chlorella sp. were respectively measured by zeta meter and Fourier transform infrared spectroscopy (FTIR). Biomass was measured by absorbance wavelength of 683 nm or dried biomass. Current results reveal that high flow rate produced more biomass than low flow rate did. Regarding to the fluorescent characteristic derived from Chlorella sp., two peaks were appeared in both wavelengths of excitation and Emission (EX/EM) respectively located at 280/330 nm (protein-like) and 440-480/680 nm (pigment). For the variation of autofluorescent intensities during algal incubation, algal image captured by epofluorescent microscope equipped with CCD (Charge-Coupled Device) could be further dealt using image software, showing that there were divergences of fluorescent intensities derived from varied amount of protein-like substance or pigment. Functional group of Chlorella sp. analyzed by FTIR, hydroxyl, peptidic bond, carboxylic acids and polysaccharide were existed with variations of transmittance (%) while gas flow rate was changed.

Solid Phase Excitation–Emission Fluorescence Method for the Classification of Complex Substances: Cortex Phellodendri and Other Traditional Chinese Medicines as Examples

A novel, simple and direct fluorescence method for analysis of complex substances and their potential substitutes has been researched and developed. Measurements involved excitation and emission (EEM) fluorescence spectra of powdered, complex, medicinal herbs, Cortex Phellodendri Chinensis (CPC) and the similar Cortex Phellodendri Amurensis (CPA); these substances were compared and discriminated from each other and the potentially adulterated samples (Caulis mahoniae (CM) and David poplar bark (DPB)). Different chemometrics methods were applied for resolution of the complex spectra, and the excitation spectra were found to be the most informative; only the rank-ordering PROMETHEE method was able to classify the samples with single ingredients (CPA, CPC, CM) or those with binary mixtures (CPA/CPC, CPA/CM, CPC/CM). Interestingly, it was essential to use the geometrical analysis for interactive aid (GAIA) display for a full understanding of the classification results. However, these two methods, like the other chemometrics models, were unable to classify composite spectral matrices consisting of data from samples of single ingredients and binary mixtures; this suggested that the excitation spectra of the different samples were very similar. However, the method is useful for classification of single-ingredient samples and, separately, their binary mixtures; it may also be applied for similar classification work with other complex substances.

Characterizing chlorine oxidation of dissolved organic matter and disinfection by‐product formation with fluorescence spectroscopy and parallel factor analysis

Relationships between chlorine demand and disinfection by‐product (DBP) formation during chlorination and fluorescence of dissolved organic matter (DOM) were developed. Fluorescence excitation and emission (EEM) spectroscopy was employed, and parameters including fluorescence index, redox index, and overall fluorescence intensity (OFI) were correlated to chlorine demand and DBP formation. The EEMs were also analyzed using a well established global parallel factor analysis (PARAFAC) model which resolves the fluorescence signal into 13 components, including quinone‐like and protein‐like components. Over an 8‐day chlorination period the OFI and sum of the 13 PARAFAC loadings decreased by more than 70%. The remaining identified quinone‐like compounds within the DOM were shifted to a more oxidized state. Quinone fluorescence was strongly correlated to both reduced fluorescence intensity and to chlorine demand which indicates that fluorescence may be used to track the chlorine oxidation of DOM. Quinone fluorescence was also correlated strongly with both classes of regulated DBPs: total trihalomethanes and haloacetic acids. Quinone‐like components were found to be strongly correlated to overall, short‐term, and long‐term specific DBP formation. The results of this study show that fluorescence is a useful tool in tracking both DOM oxidation and DBP formation during chlorination.

Reduction of Irreversible Protein Adsorption on Solid Surfaces by ProteinEngineering for IncreasedStability

The influence of protein stability on the adsorption and desorption behavior to surfaces with fundamentally different properties (negatively charged, positively charged, hydrophilic, and hydrophobic) was examined by surface plasmon resonance measurements. Three engineered variants of human carbonic anhydrase II were used that have unchanged surface properties but large differences in stability. The orientation and conformational state of the adsorbed protein could be elucidated by taking all of the following properties of the protein variants into account: stability, unfolding, adsorption, and desorption behavior. Regardless of the nature of the surface, there were correlation between (i) the protein stability and kinetics of adsorption, with an increased amplitude of the first kinetic phase of adsorption with increasing stability; (ii) the protein stability and the extent of maximally adsorbed protein to the actual surface, with an increased amount of adsorbed protein with increasing stability; (iii) the protein stability and the amount of protein desorbed upon washing with buffer, with an increased elutability of the adsorbed protein with increased stability. All of the above correlations could be explained by the rate of denaturation and the conformational state of the adsorbed protein. In conclusion, protein engineering for increased stability can be used as a strategy to decrease irreversible adsorption on surfaces at a liquid-solid interface.

Surfactant Protein A Is a Principal and Oxidation-sensitive MicrobialPermeabilizing Factor in the Alveolar LiningFluid

We have reported that surfactant protein A kills some Gram-negative organisms by increasing membrane permeability. In this study, we investigated the physiologic importance of this activity and the effect of oxidative stress on the antimicrobial functions of SP-A in vitro and in vivo. Concentrated bronchoalveolar lavage fluids from SP-A+/+ mice increased the permeability of the Escherichia coli K12 cell membrane to a greater extent than lavage from SP-A-/- animals. Similarly, calcium-dependent surfactant-binding proteins of SP-A+/+ mice increased membrane permeability more than those from SP-A-/- mice and produced greater zonal killing of agar-embedded bacteria in a radial diffusion assay. Exposure of human SP-A to copper-initiated surfactant phospholipid peroxidation or to free radicals generated by human neutrophils in vitro increased the level of SP-A-associated carbonyl moieties and blocked the permeabilizing function of the protein. We also found that exposure of mice to 90% O2 for 4 days, sufficient to lead to consumption of glutathione, oxidation of protein thiols, and accumulation of airspace protein-associated carbonyl moieties, blocked the permeabilizing activity of lavage fluid from SP-A+/+ mice. We conclude that SP-A is a major microbial permeablizing factor in lavage fluid and that oxidative stress inhibits the antibacterial activity of SP-A by a mechanism that includes oxidative modification and functional inactivation of the protein.

Scintillation and spectroscopy of the pure and Ce3+-doped elpasolites: Cs2LiYX6(X = Cl, Br)

The optical and scintillation properties of pure and Ce3+-doped Cs2LiYX6 (X = Cl,Br) are presented. X-ray-excited optical luminescence spectra, optical excitationand emission spectra, time-resolved excitation and emission spectra, scintillationpulse height spectra and scintillation decay time spectra of Ce3+-doped Cs2LiYX6(X = Cl, Br) crystals measured from 10 to 300 K are presented. Factors influencingthe scintillation mechanism and the presence of core–valence luminescence arediscussed.