Ultraviolet Fluorescence Spectroscopy Research Articles

Synthesis and Characterization of Rare Earth (Sm,Y) Light Conversion Film

In this article, Sm(Sal)xPhen, SmyY1-y(Sal)3Phen were synthesized and its films were prepared. They were characterized by infrared spectra (IR), ultra-violet visible spectrometer (UV), X-ray diffraction (XRD) and fluorescence spectroscopy. Sm/Y complexes and its mixture doped with the polyvinyl alcohol (PVA) showed photoluminescence at the wavelength of 646 nm. There was an excellent compatibility among Sm/Y complexes, the polyvinyl alcohol (PVA) and dimethyl sulphoxide (DMSO), which were used to prepare the resin film. The results indicated that Sm/Y rare earth light conversion films were better light conversion films with good compatibility in resins, and with emission wavelength suitable for plants’ photosynthesis.

The application of two-dimensional fluorescence correlation spectroscopy on the interaction between bovine serum albumin and prulifloxacin

The interaction between bovine serum albumin (BSA) and prulifloxacin was investigated by ultraviolet spectrophotometer (UV) and fluorescence spectroscopy in this paper. Two-dimensional (2D) correlation spectroscopy was applied to the analysis of fluorescence spectra. The results of spectroscopic measurements suggested that prulifloxacin (PL) have a strong ability to quench the intrinsic fluorescence of bovine serum albumin through static quenching procedure. Thermodynamic parameter enthalpy changes (ΔH) and entropy changes (ΔS) were calculated. Owing to the spectral resolution enhancement in 2D correlation spectroscopy, the structure change of prulifloxacin can be observed.

Optical properties of thiol-stabilised CdTe nanoparticles

Thiol-capped CdTe nanocrystals with cubic zinc blende structure were synthesised in aqueous solution by wet chemical route and microwave assisted method. A series of cadmium telluride (CdTe) nanoparticles capped with mercaptoacetic acid were prepared using different pH values. The synthesised nanoparticles have been characterised with Raman, FT-IR, ultraviolet visible (UV-Vis) absorption, fluorescence spectroscopy and X-ray powder diffraction (XRD) studies.

Conformational and bioactivity analysis of insulin: Freeze-drying TBA/water co-solvent system in the presence of surfactant and sugar

Despite the extensive research into the freeze-drying of aqueous solutions of proteins, it remains unknown whether proteins can survive the lyophilization process in a water-organic co-solvent system and how the process and additives affect the structural stability and activity of the proteins. In the present study, a conformational analysis of insulin in the absence/presence of bile salt and trehalose was carried out, before and after freeze-drying of a tert-butyl alcohol (TBA)/water co-solvent system at volume ratios of TBA to water ranging from 50/50 to 0/100. The study involved the use of ultraviolet derivative and fluorescence spectroscopy, circular dichroism (CD) and Fourier transform infrared (FTIR) spectroscopy. Also the bioactivity of insulin was evaluated in vivo using the streptozotocin (STZ)-induced diabetic mice as an animal model. Initial investigations indicate that the extent of the structural change of insulin depends significantly both on the TBA content and on the concentration of additives, such as sodium deoxycholate, prior to lyophilization. This could be accounted for by the phase behavior properties of the TBA/water co-solvent system, surface denaturation together with the selective and/or forced dispersion of insulin during phase separation. Lyophilized insulin in the presence of bile salt and trehalose retained more of its bioactivity and native-like structure in the solid state compared with that in the absence of additives at various TBA/water ratios, although in all cases there was a major and reversible rearrangement of secondary structure after rehydration, except for insulin at 50% TBA (v/v). Furthermore, both lyophilization in non-eutectic systems and less structural changes in the formulation process lead to more bioactivity.

Synthesis, characterization, DNA interaction and cytotoxic activities of copper complexes with ethyl 2-[bis(2-pyridylmethyl)amino]propionate

Copper(II) complexes of ethyl 2-[bis(2-pyridylmethyl)amino]propionate ligand (ETDPA) have been synthesized and characterized by elemental analyses, IR spectra, UV spectra and ES-MS. These complexes are stable in air with the formula of [(ETDPA)CuCl 2] and [(ETDPA)Cu(phen)](ClO 4) 2. The DNA-binding properties of the Cu(II) complexes have been investigated by ultraviolet spectroscopy and fluorescence spectroscopy, which showed that the binding mode of the two complexes with DNA was different. The binding mode of [(ETDPA)CuCl 2] is not the classical intercalation binding, and the binding mode of [(ETDPA)Cu(phen)](ClO 4) 2 with DNA is intercalation. The cytotoxic assay shows that the [(ETDPA)Cu(phen)](ClO 4) 2 is more active on the proliferation of cancer cells than the [(ETDPA)CuCl 2].

Characterization of Pyoverdins Secreted by a Subsurface Strain of Pseudomonas fluorescens and Their Interactions with Uranium(VI)

Fluorescent Pseudomonas species secrete pyoverdin-type siderophores with a high potential to dissolve, bind, and thus transport uranium in the environment. The formation of complexes of UO2 2 + with pyoverdins released by the groundwater bacterium Pseudomonas fluorescens (CCUG 32456) isolated at a depth of 70 m in the Äspö Hard Rock Laboratory, Sweden, was studied. Mass spectrometry indicated that the cells produce a pyoverdin–mixture with four main components: pyoverdin with a succinamide side chain, pyoverdin with a succinic acid side chain, ferribactin with a succinamide side chain, and ferribactin with a glutamic acid side chain. Three pK values could be determined from the pH-dependent changes in the absorption spectra of the pyoverdin mixture: log ß012 = 22.67 ± 0.15 (pK1 = 4.40), log ß013 = 29.15 ± 0.05 (pK2 = 6.48), and log ß014 = 33.55 ± 0.05 (pK3 = 10.47). The fluorescence properties of the pyoverdin mixture were pH-dependent. The emission maximum changed from 448 nm at pH = 2.1 to 466 nm in the pH 3.8–8.9 range. At pH > 4 a mono-exponential fluorescence decay dominates with a decay time of 5865 ± 640 ps. A drastic change in the intrinsic fluorescence properties, e.g., static fluorescence quenching, occurred due to the complex formation with UO2 2 +. Species containing UO2 2+ of the type M p L q H r were identified from the dependencies observed in the ultraviolet visible and time-resolved laser-induced fluorescence spectroscopy spectra at pyoverdin concentrations below 0.1 mM. The following average formation constants were determined: log ß112 = 30.00 ± 0.64 and log ß111 = 26.00 ± 0.85 at ionic strength I = 0.1 M (NaClO4). The determined stability constants can be used directly in safety calculations of the mobilizing effect of released pyoverdins on uranium, in uranium-contaminated environments such as mine waste disposal sites.

ULTRAVIOLET FLUORESCENCE SPECTROSCOPY (UVFS): A NEW MEANS OF DETERMINING THE EFFECT OF CHEMICAL DISPERSANTS ON OIL SPILLS

ABSTRACT Crude oils dispersed in seawater produce distinct emission spectra when exposed to ultraviolet (UV) light. The spectra can be used to estimate how effectively oil is dispersed by chemical methods. Oil dispersants (such as Corexit 9500) have a pronounced effect on water-based UV spectra, strongly enhancing emission at 445 nm. This enhancement of fluorescence over the 455 nm bandwidth is the result of dispersant breaking up higher molecular weight (>3 ring) polycyclic aromatic hydrocarbons (PAHs) into stable suspensions of small droplets. Ultraviolet fluorescence spectroscopy (UVFS) has been tested as a rapid analytical tool in the laboratory and in a wave tank designed to investigate the response of crude oils to dispersants and a range of energy dissipation rates. The results obtained with UVFS are consistent with standard chemical analyses, confirming that the method can be employed as a rapid, quantitative measure of dispersed oil concentration. Given that higher molecular weight PAHs are associated with many of the persistent toxic effects of crude oils on marine organisms, UVFS may also prove to be a useful tool for tracking these fractions during dispersed oil toxicity assays.

EFFECTS OF CHEMICAL DISPERSANTS AND MINERAL FINES ON PARTITIONING OF PETROLEUM HYDROCARBONS IN NATURAL SEAWATER

ABSTRACT The interaction of chemical dispersants and suspended sediments with crude oil influences the fate and transport of oil spills in coastal waters. Recent wave tank studies have shown that dispersants facilitate the dissipation of oil droplets into the water column and reduces the particle size distribution of oil-mineral aggregates (OMAs). In this work, baffled flasks were used to carry out a controlled laboratory experimental study to define the effects of chemical dispersants and mineral fines on the partitioning of crude oil, major fractions of oil, and petroleum hydrocarbons from the surface to the bulk water column and the sediment phases. The dissolved and dispersed oil in the aqueous phase and OMA was characterized using an Ultraviolet Fluorescence Spectroscopy (UVFS). The distribution of major fractions of crude oil (the alkanes, aromatics, resins, and asphaltenes) was analyzed by thin layer chromatography coupled to flame ionized detection (TLC/FID); aliphatic and aromatic hydrocarbons were analyzed by gas chromatography and mass spectrometry (GC/MS). The results suggest that chemical dispersants enhanced the transfer of oil from the surface to the water column as dispersed oil, and promoted the formation of oil-mineral aggregates in the water column. Interaction of chemically dispersed oil with suspended particular materials needs to be considered in order to accurately assess the environmental risk associated with chemical oil dispersant use in particle-rich nearshore and esturine waters. The results from this study indicate that there is not necessarily an increase in sedimentation of oil in particle rich water when dispersants are applied.

Nondestructive Varnish Identification by Ultraviolet Fluorescence Spectroscopy

The identification of the chemical nature of varnish is essential for art restorers in order to choose a suitable solvent during its removal. Until today, such identification has been performed using chemical analysis after sampling. An innovative technique is presented here, using ultraviolet (UV) fluorescence spectroscopy. The method is nondestructive, workable in situ, and leads to results in real time. It is based on the comparison between the emission spectrum of an unknown varnish with those of fresh, artificially aged, or old reference resins and varnishes, for different monochromatic excitation wavelengths. The resin and the nature of the varnish as spirit, oil, or mixed can thus be identified. Various examples are presented on home-made samples applied on fluorescent backgrounds and on real works of art.

Study on successively preparation of nano-TiO 2 ethanol colloids by pulsed laser ablation and fluorescence property

Nano-TiO 2 colloids have been successively prepared by focused, pulsed laser ablation (PLA) at the interface of solid titanium dioxide and flowing liquid. Three factors influenced the luminescence of the nano-TiO 2 colloids. The first factor was the flowing rates of the flowing liquid. The second factor was the pulsed laser output power. The third factor was the age of the colloids. The nano-TiO 2 colloids products were characterized by transmission electron microscopy (TEM), ultraviolet visible spectroscopy (UV–vis) and fluorescence spectroscopy. The results revealed that anhydrous ethanol was the best flowing liquid, and cyclohexane or water was found to be not suitable for this system; under the conditions of the lowest flowing rates of the flowing liquids in the range of 0.017–0.15 mL/s, the highest pulsed laser output power in the range of 100–250 mJ/pulse and with the proper aging time of the colloids, nano-TiO 2 ethanol colloids with strong fluorescence emission intensity at about 414 nm can be obtained.

Canine cancer screening via ultraviolet absorbance and fluorescence spectroscopy of serum proteins

A cost-effective optical cancer screening and monitoring technique was demonstrated in a pilot study of canine serum samples and was patented for commercialization. Compared to conventional blood chemistry analysis methods, more accurate estimations of the concentrations of albumin, globulins, and hemoglobin in serum were obtained by fitting the near UV absorbance and photoluminescence spectra of diluted serum as a linear combination of component reference spectra. Tracking these serum proteins over the course of treatment helped to monitor patient immune response to carcinoma and therapy. For cancer screening, 70% of dogs with clinical presentation of cancer displayed suppressed serum hemoglobin levels (below 20 mg/dL) in combination with atypical serum protein compositions, that is, albumin levels outside of a safe range (from 4 to 8 g/dL) and globulin levels above or below a more normal range (from 1.7 to 3.7 g/dL). Of the dogs that met these criteria, only 20% were given a false positive label by this cancer screening test.

Structural Study of BSA/Poly(ethylene glycol) Lipid Conjugate Complexes

In this work we report the structural characteristics of bovine serum albumin/poly(ethylene glycol) lipid conjugate (BSA/PEG(2000)-PE) complexes under physiological conditions (37 degrees C and pH 7.4) for particular fractions of BSA to PEG-lipid concentration, c(BSA)/c(PEG)(2000)-PE. Ultraviolet fluorescence spectroscopy (UV) results shown that PEG(2000)-PE is associated to BSA, leading to protein unfolding for fixed c(BSA) = 0.01 wt % and variable c(PEG)(2000)-PE = 0.0015-0.6 wt %. Tryptophan groups on the BSA surface are in contact with the PEG-lipid at c(PEG)(2000)-PE = 0.0015 wt %, while they are exposed to water at c(PEG)(2000)-PE > 0.0015 wt %. Dynamic and static light scattering (DLS and SLS) and small-angle neutron scattering (SANS) point out the existence of individual BSA/PEG-lipid complexes in the system for fixed c(BSA) = 1 wt % and variable c(PEG)(2000)-PE = 0.15-2 wt %. DLS shows that there is only one BSA molecule per protein/PEG-lipid complex, while SLS shows that the PEG-lipid associates to the BSA without promoting aggregation between adjacent protein/polymer-lipid conjugate complexes. SANS was used to show that BSA/PEG(2000)-PE complexes adopt an oblate ellipsoidal shape. Partially unfolded BSA is contained in the core of the oblate ellipsoid, which is surrounded by an external shell containing the PEG(2000)-PE.

Complex Formation of Bovine Serum Albumin with a Poly(ethylene glycol) Lipid Conjugate

In this work, we report the formation of complexes by self-assembly of bovine serum albumin (BSA) with a poly(ethylene glycol) lipid conjugate (PEG2000-PE) in phosphate saline buffer solution (pH 7.4). Three different sets of samples have been studied. The BSA concentration remained fixed (1, 0.01, or 0.001 wt % BSA) within each set of samples, while the PEG2000-PE concentration was varied. Dynamic light scattering (DLS), rheology, and small-angle X-ray scattering (SAXS) were used to study samples with 1 wt % BSA. DLS showed that BSA/PEG2000-PE aggregates have a size intermediate between a BSA monomer and a PEG2000-PE micelle. Rheology suggested that BSA/PEG2000-PE complexes might be surrounded by a relatively compact PEG-lipid shell, while SAXS results showed that depletion forces do not take an important role in the stabilization of the complexes. Samples containing 0.01 wt % BSA were studied by circular dichroism (CD) and ultraviolet fluorescence spectroscopy (UV). UV results showed that at low concentrations of PEG-lipid, PEG2000-PE binds to tryptophan (Trp) groups in BSA, while at high concentrations of PEG-lipid the Trp groups are exposed to water. CD results showed that changes in Trp environment take place with a minimal variation of the BSA secondary structure elements. Finally, samples containing 0.001 wt % BSA were studied by zeta-potential experiments. Results showed that steric interactions might play an important role in the stabilization of the BSA/PEG2000-PE complexes.

Spectroscopic Distribution of Dissolved Organic Matter in a Dam Reservoir Impacted by Turbid Storm Runoff

Spectroscopic characteristics of dissolved organic matter (DOM) in a large dam reservoir were determined using ultraviolet absorbance and fluorescence spectroscopy to investigate spatial distribution of DOM composition after turbid storm runoff. Water samples were collected along a longitudinal axis of the reservoir at three to four depths after a severe storm runoff. Vertical profiles of turbidity data showed that a turbid water layer was located at a middle depth of the entire reservoir. The spectroscopic characteristics of DOM samples in the turbid water layer were similar to those of terrestrial DOM, as demonstrated by the higher specific UV absorbance (SUVA) and the lower fluorescence emission intensity ratio (F(450)/F(500)) compared to other surrounding DOM samples in the reservoir. Synchronous fluorescence spectroscopy revealed that higher content of humic-like DOM composition was contained in the turbid water. Fluorescence excitation-emission matrix (EEM) showed that lower content of protein-like aromatic amino acids was present in the turbid water DOM. The highest protein-like fluorescence was typically observed at a bottom layer of each sampling location. The bottom water DOM exhibited extremely high protein-like florescence near the dam site. The particular observation was attributed to the low water temperature and the isolation of the local bottom water due to the upper location of the withdrawal outlet near the dam. Our results suggest that the distribution of DOM composition in a dam reservoir is strongly influenced by the outflow operation, such as selective withdrawal, as well as terrestrial-origin DOM inputs from storm runoff.

Plasmid DNA acquires immunogenicity on exposure to singlet oxygen

In the present study, the effect of singlet oxygen (1O2) (generated by ultraviolet (UV) irradiation of methylene blue) on plasmid DNA has been analyzed by UV spectroscopy, fluorescence spectroscopy, and S1 nuclease digestibility. Both native and 1O2-modified plasmid DNA were treated with a number of restriction enzymes to map out the sites damaged by 1O2. It was also observed that, on exposure to 1O2, native plasmid DNA that is non-immunogenic acquired the ability to elicit an immune response in experimental animals. However, the induced antibodies exhibited appreciable cross reactivity with various polynucleotides and nucleic acids. The data indicate that the antibodies, though cross-reactive, preferentially bind 1O2-modified epitopes on plasmid DNA. Gel retardation assay further substantiated the enhanced recognition of 1O2-modified plasmid DNA over the native form. The antibodies developed were then subjected to competition ELISA with sera from various diseases such as systemic lupus erythematosus, rheumatoid arthritis, and cancer. These results suggest that upon exposure of DNA to 1O2, neo-epitopes are generated, which may be one of the factors for the induction of circulating autoantibodies in the three diseases.

Laboratory Study of O(1S) Formation Process in the Photolysis of O3 and its Atmospheric Implications

A high-sensitive technique to detect O(1S) atoms using vacuum ultraviolet laser-induced fluorescence (VUV-LIF) spectroscopy has been applied to study the O(1S) production process from the UV photodissociation of O3, N2O, and H2O2. The quantum yields for O(1S) formation from O3 photolysis at 215 and 220 nm are determined to be (1.4 ± 0.4) × 10−4 and (5 ± 3) × 10−5, respectively. Based on thermochemical considerations, the O(1S) formation from O3 photolysis at 215 and 220 nm is attributed to a spin-forbidden process of O(1S)+O2(X3Σg −). Analysis of the Doppler profile of O(1S) produced from O3 photolysis at 193 nm also indicates that the O(1S) atoms are produced from the spin-forbidden process. In the photolysis of N2O and H2O2 at 193 nm, no discernible signal of O(1S) atoms has been detected. The upper limit values of the quantum yields for O(1S) production from N2O and H2O2 photolysis at 193 nm are estimated to be 8 × 10−5 and 3 × 10−5, respectively. Using the experimental results, the impact of the O(1S) formation from O3 photolysis on the atmospheric OH radical formation through the reaction of O(1S)+H2O has been estimated. The calculated results show that the contribution of the O(1S)+H2O reaction to the OH production rate is ∼2% of that of the O(1D)+H2O reaction at 30 km altitude in mid-latitude. Implications of the present laboratory experimental results for the terrestrial airglow of O(1S) at 557.7 nm have also been discussed.

Interactions of some modified mono- and bis-β-cyclodextrins with bovine serum albumin

Two mono-substituted β-cyclodextrins and two bridged bis-β-cyclodextrins, that is, mono(6-(2-aminoethylamino)-6-deoxy)-β-cyclodextrin (1), mono(6-(2-(2-aminoethylamino)ethylamino)-6-deoxy)-β-cyclodextrin (2), ethylene-1,2-diamino bis-6-(6-deoxy-β-cyclodextrin) (3), and iminodiethylene-2,2′-diamino bis-6-(6-deoxy-β-cyclodextrin) (4), were prepared from β-cyclodextrin. Their binding ability with bovine serum albumin as a model protein was investigated through proton magnetic resonance (1H NMR), ultraviolet visible spectroscopy (UV–vis), circular dichroism (CD), and fluorescence spectroscopy. In the 1H NMR spectra of the modified cyclodextrins, the resolution of proton signals decreases after the addition of BSA. From the UV and CD spectra, it is found that both the UV absorption and the α-helix content of BSA increase with the concentration of the modified cyclodextrins. The protein–ligand interactions cause a fluorescence quenching. The quenching constants are determined using the Stern–Volmer equation to provide an observation of the binding affinity between modified cyclodextrins and BSA. All these results indicate that the modified cyclodextrins can interact with BSA and the bridged bis(β-cyclodextrin)s (3 and 4) have much stronger interactions than the mono-substituted β-cyclodextrins (1 and 2). The strong binding stability of bis-cyclodextrins should be attributed to the cooperative effect of two adjacent cyclodextrin moieties. Job’s plot shows that the complex stoichiometries of BSA to the modified cyclodextrins were 1:4 for 1 and 2, as well as 1:3 for 3 and 4, respectively.

Analysis of the Thermal and pH Stability of Human Respiratory Syncytial Virus

Respiratory syncytial virus (RSV) was studied as a function of pH (3-8) and temperature (10-85 degrees C) by fluorescence, circular dichroism, and high-resolution second-derivative absorbance spectroscopies, as well as dynamic light scattering and optical density as a measurement of viral aggregation. The results indicate that the secondary, tertiary, and quaternary structures of RSV are both pH and temperature labile. Derivative ultraviolet absorbance and fluorescence spectroscopy (intrinsic and extrinsic) analyses suggest that the stability of tertiary structure of RSV proteins is maximized near neutral pH. In agreement with these results, the secondary structure of RSV polypeptides seems to be more stable at pH 7-8, as evaluated by circular dichroism spectroscopy. The integrity of the viral particles studied by turbidity and dynamic light scattering also revealed that RSV is more thermally stable near neutral pH and particularly prone to aggregation below pH 6. By combination of the spectroscopic data employing a multidimensional eigenvector phase space approach, an empirical phase diagram for RSV was constructed. The pharmaceutical utility of this approach and the optimal formulation conditions are discussed.

Rate constants of the O( 1D) reactions with N 2, O 2, N 2O, and H 2O at 295 K

Using a technique of laser flash photolysis coupled with vacuum ultraviolet laser-induced fluorescence spectroscopy, the rate coefficients of O( 1D) reactions with N 2, O 2, N 2O, and H 2O at 295 ± 2 K have been determined to be k N 2 = ( 3 . 29 ± 0 . 27 ) × 10 - 11 , k O 2 = ( 4 . 06 ± 0 . 24 ) × 10 - 11 , k N 2 O = ( 1 . 35 ± 0 . 08 ) × 10 - 10 and k H 2 O = ( 2 . 07 ± 0 . 18 ) × 10 - 10 cm 3 molecule - 1 s - 1 . The quoted uncertainties include estimated errors and are the 95% confidence level. The k N 2 and k N 2 O values obtained are larger than the current NASA/JPL recommendations by 26% and 16%, respectively, although they are still within the error limits associated with the recommendations.

Laser-induced fluorescence study of the quenching of Cl( 2P 1/2) in collisions with N 2 molecules and rare gas atoms

The rate constants of physical quenching of Cl( 2P 1/2) in collisions with N 2 molecules and rare gas atoms (Rg = He, Ne and Ar) at 295 ± 2 K were investigated using a technique of vacuum ultraviolet laser-induced fluorescence spectroscopy. The rate constants determined are (7.6 ± 0.8) × 10 −15, (5.7 ± 0.3) × 10 −14, ⩽8 × 10 −16 and ⩽5 × 10 −16 cm 3 molecule −1 s −1 for collision partners of N 2, He, Ne and Ar, respectively.