UV Absorption Measurements Research Articles

Coumarin-Phosphazenes: Enhanced Photophysical Properties from Hybrid Materials.

Phosphazenes have drawn a great deal of interest over the past 20 years as a potentially useful building block for the fabrication of fluorescent materials. The main objective of this work is to explore novel derivatives produced by coumarins, a class of chemicals well-known for their photophysical importance, and cyclophosphazenes. UV absorbance, fluorescence emission, quantum yield, and lifetime measurements were conducted to comprehend the optical properties. Furthermore, single-crystal X-ray analysis and theoretical calculations were carried out to confirm the structure of the molecule. The obtained findings collectively confirm the commendable optical properties exhibited by the studied compounds. Moreover, a detailed study of the crystal packing arrangement of DPP-Et-Kum-Et compound crystallized in the P21/n monoclinic space group revealed the presence of stacking interactions between the nonplanar conjugated benzene rings of the coumarins and the rigid diphenyl groups attached to the phosphazene ring. The crystal structure of the DPP-Kum-Me-Me compound is mainly based on classical C-H···O intermolecular hydrogen bonding interactions with an average distance of 2.52 Å. Importantly, the calculated absorption spectra of the compounds are in close agreement with the experimental data, further supporting their interesting electronic properties. Given that the DPP-Et-Kum-Et and DPP-Kum-Et compounds have the theoretically lowest band gaps (4.31 and 4.30 eV, respectively), the activation energies of these compounds were determined by an impedance analyzer using dc conductance values measured at different temperatures. The calculated activation energies for DPP-Et-Kum-Et and DPP-Kum-Et are 104.49 and 100.92 meV, respectively. The results demonstrate that both theoretical and experimental calculations are in agreement with each other and that the DPP-Kum-Et compound has the lowest conductivity.

Evaluating the biomolecular interaction between delamanid/formulations and human serum albumin by fluorescence, CD spectroscopy and SPR: Effects on protein conformation, kinetic and thermodynamic parameters

Delamanid is an anti-tuberculosis drug used for the treatment of drug-resistant tuberculosis. Since delamanid has a high protein bound potential, even patients with low albumin levels should experience high and rapid delamanid clearance. However, the interaction between delamanid and albumin should be better controlled to optimize drug efficacy. This study was designed to evaluate the binding characteristics of delamanid to human serum albumin (HSA) using various methods: fluorescence spectroscopy, circular dichroism (CD), surface plasmon resonance (SPR), and molecular docking simulation. The fluorescence emission band without any shift indicated the interaction was not affected by the polarity of the fluorophore microenvironment. The reduction of fluorescence intensity at 344 nm was proportional to the increment of delamanid concentration as a fluorescence quencher. UV-absorbance measurement at the maximum wavelength (λmax, 280 nm) was evaluated using inner filter effect correction. The HSA conformation change was explained by the intermolecular energy transfer between delamanid and HSA during complex formation. The study, which was conducted at temperatures of 298 K, 303 K, and 310 K, revealed a static quenching mechanism that correlated with a decreased of bimolecular quenching rate constant (kq) and binding constant (Ka) at increased temperatures. The Ka was 1.75–3.16 × 104 M−1 with a specific binding site with stoichiometry 1:1. The negative enthalpy change, negative entropy change, and negative Gibbs free energy change demonstrated an exothermic-spontaneous reaction while van der Waals forces and hydrogen bonds played a vital role in the binding. The molecular displacement approach and molecular docking confirmed that the binding occurred mainly in subdomain IIA, which is a hydrophobic pocket of HSA, with a theoretical binding free energy of −9.33 kcal/mol. SPR exhibited a real time negative sensorgram that resulted from deviation of the reflex angle due to ligand delamanid-HSA complex forming. The binding occurred spontaneously after delamanid was presented to the HSA surface. The SPR mathematical fitting model revealed that the association rate constant (kon) was 2.62 × 108 s−1M−1 and the dissociation rate constant (koff) was 5.65 × 10−3 s−1. The complexes were performed with an association constant (KA) of 4.64 × 1010 M−1 and the dissociation constant (KD) of 2.15 × 10−11 M. The binding constant indicated high binding affinity and high stability of the complex in an equilibrium. Modified CD spectra revealed that conformation of the HSA structure was altered by the presence of delamanid during preparation of the proliposomes that led to the reduction of secondary structure stabilization. This was indicated by the percentage decrease of α-helix. These findings are beneficial to understanding delamanid-HSA binding characteristics as well as the drug administration regimen.

The mRNACalc webserver accounts for the N1-methylpseudouridine hypochromicity to enable precise nucleoside-modified mRNA quantification

Nucleoside-modified messenger RNA (mRNA) technologies necessarily incorporate N1-methylpseudouridine into the mRNA molecules to prevent the over-stimulation of cytoplasmic RNA sensors. Despite this modification, mRNA concentrations remain mostly determined through the measurement of UV absorbance at 260nm wavelength (A260). Herein, we report that the N1-methylpseudouridine absorbs approximately 40% less UV light at 260nm than uridine, and its incorporation into mRNAs leads to the under-estimation of nucleoside-modified mRNA concentrations, with 5%-15% error, in an mRNA-sequence-dependent manner. We therefore examined the RNA quantification methods and developed the mRNACalc webserver. It accounts for the molar absorption coefficient of modified nucleotides at 260nm wavelength, the RNA composition of the mRNA, and the A260 of the mRNA sample to enable accurate quantification of nucleoside-modified mRNAs.

Investigation on the Validity of in vitro Sun Protection Factor and Ultraviolet-A Protection Factor Evaluation Method for Sunscreen Samples.

Factors affecting the in vitro Sun Protection Factor (SPF) and Ultraviolet-A Protection Factor (UVA-PF) of sunscreens were analyzed for verifying the validity and reliability of the ISO24443 evaluation method. UV absorbance measurements by different spectrophotometers did not lead to the large difference in in vitro SPF/UVA-PF, although the UV absorbance determined by each spectrophotometer exhibited relatively large difference when it was larger than 2. On the other hand, relatively large difference was found in in vitro SPF/UVA-PF by utilizing European Cosmetic and Perfumery Association (Colipa) 1994 or UV-solar simulated radiation (UV-SSR) for the spectral irradiance. Appropriateness of employing the coefficient of adjustment for the determination of in vitro UVA-PF was also found to be reexamined.

Using UV absorption measurements for estimation of laser damage thresholds in ultrafast laser applications

Laser damage for ultrafast pulses is connected to the UV absorption edge via bandgap. This connection may be used to facilitate damage testing and thus coating development. Preliminary results are presented here.

A feasibility study on exhaled breath analysis using UV spectroscopy to detect COVID-19

A 23-subject feasibility study is reported to assess how UV absorbance measurements on exhaled breath samples collected from silicon microreactors can be used to detect COVID-19. The silicon microreactor technology chemoselectively preconcentrates exhaled carbonyl volatile organic compounds and subsequent methanol elution provides samples for analysis. The underlying scientific rationale that viral infection will induce an increase in exhaled carbonyls appears to be supported by the results of the feasibility study. The data indicate statistically significant differences in measured UV absorbance values between healthy and symptomatic COVID-19 positive subjects in the wavelength range from 235 nm to 305 nm. Factors such as subject age were noted as potential confounding variables.

Conformation-dependent UV inactivation efficiency of a conjugative, multi-drug resistant plasmid

A conjugative, multi-drug-resistant plasmid was irradiated in-vivo and in-vitro with a 265-nm UV-light emitting diode (UV-LED) to investigate the gene inactivation efficiency of a plasmid deoxyribonucleic acid (pDNA) carrying DNA transfer and replication genes. The clinical-isolate 60 kb RP4 plasmid of the IncPα group containing the traG gene, was irradiated intracellularly in E. coli DH5α and extracellularly in a water medium at pH 8.5. Real-time quantitative polymerase chain reaction (RT-qPCR) measurements of the UV-fluence response gene inactivation rate constants revealed a decreasing pattern via a pseudo-1st-order inactivation kinetics in all forms examined. Our findings showed that the intracellular-supercoiled conformation, with k = 6.1 × 10-3 cm2/mJ, has the lowest UV susceptibility (lowest inactivation rate). UV absorbance measurements and a computational approach showed that the host's RNA provides the photo-shielding, demonstrating this high UV resistance. When UV exposure was measured in-vitro, the condensed DNA exhibited a self-shielding effect over supercoiled and denatured DNA due to the hypochromic-hyperchromic effects. This study has shown that large-sized conjugative plasmids with conformation-dependent UV/UV-LED-based gene inactivation play a significant role in preventing the spread of antibiotic resistance.

Monitoring ascorbic acid oxidation with H2O2 and analyzing the food supplement product using parallel factor analysis model of kinetic UV absorption measurements

Ascorbic acid is a functional compound in maintaining the physiological processes of humans who acquire it from dietary sources, and also functions as an antioxidant. Therefore, the quantitation, and degradation of ascorbic acid in the food matrix and its interaction with coexisting components is a very important issue in terms of food safety and human health. Classical analytical methods may not give the expected results in the analysis of more advanced and complex food products obtained with the developing production technology. In this perspective, the parallel factor analysis (PARAFAC) model using kinetic UV absorption measurements was improved for the co-estimation of the kinetics and quantification of ascorbic acid in a food supplement product, which is a commercial effervescent preparation without requiring a prior separation step. The proposed three-way analysis strategy was validated and applied to the analysis of the relevant samples. For example, in the test samples, percent recovery and relative standard deviation were found to be 99.4 % and 1.36 %, respectively. The proposed chemometric strategy would be an alternative approach with a good selectivity for estimating the kinetics and quantification of ascorbic acid in a commercial supplementary product. The assay results of the PARAFAC model was checked by using ultra-performance liquid chromatography (UPLC).

A High-Performance Antibacterial Nanostructured ZnO Microfluidic Device for Controlled Bacterial Lysis and DNA Release.

In this work, the antibacterial properties of nanostructured zinc oxide (ZnO) surfaces are explored by incorporating them as walls in a simple-to-fabricate microchannel device. Bacterial cell lysis is demonstrated and quantified in such a device, which functions due to the action of its nanostructured ZnO surfaces in contact with the working fluid. To shed light on the mechanism responsible for lysis, E. coli bacteria were incubated in zinc and nanostructured ZnO substrates, as well as the here-investigated ZnO-based microfluidic devices. The unprecedented killing efficiency of E. coli in nanostructured ZnO microchannels, effective after a 15 min incubation, paves the way for the implementation of such microfluidic chips in the disinfection of bacteria-containing solutions. In addition, the DNA release was confirmed by off-chip PCR and UV absorption measurements. The results indicate that the present nanostructured ZnO-based microfluidic chip can, under light, achieve partial inactivation of the released bacterial DNA via reactive oxygen species-mediated oxidative damage. The present device concept can find broader applications in cases where the presence of DNA in a sample is not desirable. Furthermore, the present microchannel device enables, in the dark, efficient release of bacterial DNA for downstream genomic DNA analysis. The demonstrated potential of this antibacterial device for tailored dual functionality in light/dark conditions is the main novel contribution of the present work.

Three-dimensional strategies in the quantitative resolution of kinetic UV absorbance measurements for monitoring the oxidation of quercetin by oxidant agents and analyzing dietary supplement product

Three-dimensional strategies involving the application of parallel factor analysis (PARAFAC) to the kinetic UV absorbance measurements were elaborated to monitor the oxidation of quercetin with oxidant agents (K2Cr2O7 and KIO3) and to quantify analyte in a dietary supplement product. Loadings (spectral, kinetic and concentration profiles) were obtained by the PARAFAC deconvolution. Spectral identification, kinetics and quantification of the relevant analyte in the presence of interferent(s) were performed. The elaborated chemometric strategies were carefully validated to demonstrate the capability of the method. Assay results of the PARAFAC strategies were statistically compared to that of the newly developed UPLC method.

Scaling-Up Seeded Hydrothermal Nanowire Synthesis on Non-planar Surfaces Using a Flow Reactor

While many nanomaterial synthesis processes have been demonstrated at the laboratory scale, grand challenges remain at the nanomanufacturing frontier, where it is necessary to maintain tunable material structure and properties at large length scales using high-throughput, low-cost, and sustainable processes. Seeded hydrothermal synthesis is widely used to generate tunable nanostructures with controlled geometric parameters. In this study, we used atomic layer deposition to deposit precise and conformal seed layers which were subsequently processed using a customized hydrothermal flow reactor. The reactor design allows for control of the solution temperature profile in space and time, as well as the solution flow profile. Recirculation of the hydrothermal growth solution enables reduction of the chemical waste by 77–92% compared to a single pass flow reactor. This “surface-directed assembly” process allows for the growth of vertically aligned zinc oxide (ZnO) nanowires (NWs) directly onto macroscopic (cm-scale) non-planar surfaces. We quantify the uniformity of the NW morphology using scanning electron microscopy and UV absorption measurements. The NWs were further functionalized to form superhydrophobic and optically transparent surface coatings along a curved glass dome substrate. The surface coatings were shown to significantly reduce the rate of biofouling from marine algae by ∼75%. This demonstrates a pathway for the scale-up of hydrothermal synthesis processes with a variety of applications in the biological and environmental fields, including medical devices and optical and oceanographic sensors.

UV spectroscopy: A novel method for determination of degree of substitution of phthaloyl group as amine protector in chitosan

Abstract The purpose of this study is to introduce and develop a new experimental method based on UV spectroscopy for measuring the degree of substitution (DS) of phthaloyl group used for protecting amine group in chitosan, a biopolymer derived from chitin that has a wide variety of applications including drug delivery in pharmaceutical products. N-phthaloylated chitosan was synthesized and the UV absorption measurements were performed on its solutions with different DS with concentrations of 6.25, 12.5, 25, 50, and 100 μg/mL in DMSO at 295 nm. The accuracy of the method was checked with H-NMR and there was consistency between the results obtained by two methods. This suggests that the UV spectroscopy can be a potential method for the characterization of the polymer and can replace the difficult methods of analysis used for the chemical structure.

Effect and Mechanism of Eliminating Staphylococcus aureus by Electron Beam Irradiation and Reducing the Toxicity of Its Metabolites.

The purpose of this study was to evaluate the mechanism of sterilization of Staphylococcus aureus by electron beam irradiation (0.5-, 1-, 2-, 4-, and 6-kGy treatments) and whether it reduces the toxicity of its fermentation supernatant. In this study, we investigated the mechanism of sterilization of S. aureus by electron beam irradiation using colony count, membrane potential, intracellular ATP, and UV absorbance measurements; we used hemolytic, cytotoxic, and suckling mouse wound models to verify that electron beam irradiation reduced the toxicity of the S. aureus fermentation supernatant. The results showed that 2 kGy of electron beam irradiation treatment completely inactivated S. aureus in suspension culture, and 4 kGy inactivated cells in S. aureus biofilms. This study suggests that the bactericidal effect of electron beam irradiation on S. aureus may be attributed to reversible damage to the cytoplasmic membrane, resulting in its leakage and the significant degradation of genomic DNA. The combined results of hemolytic, cytotoxic, and suckling mouse wound models demonstrated that the toxicity of S. aureus metabolites was significantly reduced when the electron beam irradiation dose was 4 kGy. In summary, electron beam irradiation has the potential to control S. aureus and reduce its toxic metabolites in food. IMPORTANCE Electron beam irradiation of >1 kGy damaged the cytoplasmic membrane, and reactive oxygen species (ROS) penetrated the cells. Electron beam irradiation of >4 kGy reduces the combined toxicity of virulent proteins produced by Staphylococcus aureus. Electron beam irradiation of >4 kGy can be used to inactivate Staphylococcus aureus and biofilms on milk.

Insertion of Ga-MoO3 thin film at Cu/p-Si interface for the fabrication of MIS structure Schottky barrier diodes

The fabrication of a metal-insulator-semiconductor diode with a pure MoO3 and different weight % of Ga-MoO3 (5, 10, and 15 wt%) thin film insulator layer grown by JNSP techniques. The obtained films were characterized for structural analysis by XRD exposing multiphase of orthorhombic and monoclinic with 10 wt% of Ga-based film with higher crystallite size. FE-SEM images display plate-like structures. UV absorption measurements recorded a band gap of 3.15 eV for 10 wt% Ga doped film. X-ray photoelectron spectroscopy (XPS) investigates is described by the utmost oxidation state. The DC electrical conductivity of the films increased for higher wt% of Ga up to 10 wt%. The I-V characteristic curve of the Cu/Ga-MoO3/p-Si diode parameters n, ФB, PS, R, QE, and D* shows that, current flows predominantly across the interfaces as a result of carrier missioning. In addition, we observed significantly high photocurrent performance from the Cu/Ga-MoO3/p-Si diode under visible light illumination.

Stability and activity of titanium oxynitride thin films for the electrocatalytic reduction of nitrogen to ammonia at different pH values.

The production of ammonia for agricultural and energy demands has accelerated research for more environmentally-friendly synthesis options, particularly the electrocatalytic reduction of molecular nitrogen (nitrogen reduction reaction, NRR). Catalyst activity for NRR, and selectivity for NRR over the competitive hydrogen evolution reaction (HER), are critical issues for which fundamental knowledge remains scarce. Herein, we present results regarding the NRR activity and selectivity of sputter-deposited titanium nitride and titanium oxynitride films for NRR and HER. Electrochemical, fluorescence and UV absorption measurements show that titanium oxynitride exhibits NRR activity under acidic conditions (pH 1.6, 3.2) but is inactive at pH 7. Ti oxynitride is HER inactive at all these pH values. In contrast, TiN - with no oxygen content upon deposition - is both NRR and HER inactive at all the above pH values. This difference in oxynitride/nitride reactivity is observed despite the fact that both films exhibit very similar surface chemical compositions - predominantly TiIV oxide - upon exposure to ambient, as determined by ex situ X-ray photoelectron spectroscopy (XPS). XPS, with in situ transfer between electrochemical and UHV environments, however, demonstrates that this TiIV oxide top layer is unstable under acidic conditions, but stable at pH 7, explaining the inactivity of titanium oxynitride at this pH. The inactivity of TiN at acidic and neutral pH is explained by DFT-based calculations showing that N2 adsorption at N-ligated Ti centers is energetically significantly less favorable than at O-ligated centers. These calculations also predict that N2 will not bind to TiIV centers due to a lack of π-backbonding. Ex situ XPS measurements and electrochemical probe measurements at pH 3.2 demonstrate that Ti oxynitride films undergo gradual dissolution under NRR conditions. The present results demonstrate that the long-term catalyst stability and maintenance of metal cations in intermediate oxidation states for pi-backbonding are critical issues worthy of further examination.

Compositional Analysis of ssDNA-Coated Single-Wall Carbon Nanotubes through UV Absorption Spectroscopy.

Aqueous suspensions of single-wall carbon nanotubes (SWCNTs) coated by ssDNA are analyzed using UV absorption and total carbon measurements. The results give absolute average concentrations of both components in samples without free ssDNA. From those values, the average mid-UV SWCNT absorptivity is deduced for three different batches of relatively small diameter nanotubes: two HiPco and one CoMoCAT. The absorptivity values enable the use of simple spectrophotometry to measure absolute concentrations of similar SWCNT samples in aqueous SDS. The results also quantify the mass ratio of ssDNA to SWCNT, defining the average number of nanotube carbon atoms suspended by one ssDNA strand of T15GT15 or T30G. Comparing this experimental parameter with results from replica exchange molecular dynamics simulations of one ssDNA strand freely adsorbed on a (6,5) segment shows close agreement between the computed number of SWCNT atoms covered per strand and the measured number of SWCNT atoms suspended per strand.

Determination of the protein content of complex samples by aromatic amino acid analysis, liquid chromatography-UV absorbance, and colorimetry

Fast and accurate determination of the protein content of a sample is an important and non-trivial task of many biochemical, biomedical, food chemical, pharmaceutical, and environmental research activities. Different methods of total protein determination are used for a wide range of proteins with highly variable properties in complex matrices. These methods usually work reasonably well for proteins under controlled conditions, but the results for non-standard and complex samples are often questionable. Here, we compare new and well-established methods, including traditional amino acid analysis (AAA), aromatic amino acid analysis (AAAA) based on the amino acids phenylalanine and tyrosine, reversed-phase liquid chromatography of intact proteins with UV absorbance measurements at 220 and 280 nm (LC-220, LC-280), and colorimetric assays like Coomassie Blue G-250 dye-binding assay (Bradford) and bicinchoninic acid (BCA) assay. We investigated different samples, including proteins with challenging properties, chemical modifications, mixtures, and complex matrices like air particulate matter and pollen extracts. All methods yielded accurate and precise results for the protein and matrix used for calibration. AAA, AAAA with fluorescence detection, and the LC-220 method yielded robust results even under more challenging conditions (variable analytes and matrices). These methods turned out to be well-suited for reliable determination of the protein content in a wide range of samples, such as air particulate matter and pollen.

Synthesis, Structure, and Properties of Unsaturated Thiacrown Ethers Possessing Sulfonium Groups.

Thiacrown ethers have attracted much attention in host-guest chemistry. Herein, we present the polymethylation reactions of unsaturated thiacrown ethers. Unsaturated thiacrown ethers having sulfonium groups were synthesized by the reaction of corresponding unsaturated thiacrown ethers with methyl triflate. The obtained methylated unsaturated thiacrown ethers were characterized by single-crystal X-ray diffraction analysis, UV absorption measurement, and cyclic voltammetry. The occupied and unoccupied molecular orbitals of the obtained methylated unsaturated thiacrown ethers are essentially localized respectively around the sulfide groups and the sulfonium groups. Furthermore, the results of electrostatic potential maps indicated that positive charges were distributed throughout the entire unsaturated thiacrown ether moieties.

Application of UV absorbance and electron-donating capacity as surrogates for micropollutant abatement during full-scale ozonation of secondary-treated wastewater

Ozonation of secondary-treated wastewater for the abatement of micropollutants requires a reliable control of ozone doses. Changes in the UV absorbance of dissolved organic matter (DOM) during ozonation allow to estimate micropollutant abatement on-line and were therefore identified as feed-back control parameter. In this study, the suitability of the electron-donating capacity (EDC) as an additional surrogate parameter which is independent of optical DOM properties was evaluated during full-scale ozonation. For this purpose, a recently developed EDC analyzer was enhanced to enable continuous on-line EDC and UV absorbance measurements. During a multi-week monitoring campaign at the wastewater treatment plant of Zurich, Switzerland, specific ozone doses were varied from 0.13 to 0.91 mgO3⋅mgDOC−1 and selected micropollutants with different ozone reactivities were analyzed by LC-MS in conjunction with bromate analysis by IC-MS. In agreement with previous laboratory studies, the relative residual UV absorbance and EDC both decreased exponentially as a function of the specific ozone dose and, in comparison to the residual UV absorbance, residual EDC values showed a more pronounced decrease at low specific ozone doses ≤0.34 mgO3⋅mgDOC−1. Logistic regression models allowed to estimate relative residual micropollutant concentrations in the ozonation effluent using either the residual UV absorbance or EDC as explanatory variable. Averaging those models along the explanatory variables allowed to estimate target values in relative residual UV absorbances and EDC for specific micropollutant abatement targets. In addition, both parameters allowed to identify conditions with elevated conversions of bromide to bromate. Taken together, these findings show that the integration of relative residual EDC values as a second control parameter can improve existing absorbance-based ozonation control systems to meet micropollutant abatement targets, particularly for treatment systems where low ozone doses are applied.

Emission Intensity Enhancement for Iridium(III) Complex in Dimethyl Sulfoxide under Photoirradiation.

We found emission intensity enhancement for fac-Ir(ppy)3 (ppy = 2-(2'-phenyl)pyridine) in aerated dimethyl sulfoxide (DMSO) during photoirradiation for the first time. This phenomenon was concluded to be responsible for the consumption of 3O2 dissolved in DMSO through dimethyl sulfone production by photosensitized reaction using fac-Ir(ppy)3. A 3O2 adduct of DMSO molecule was detected by UV absorption measurement and theoretical calculation. We proposed a mechanism for the emission enhancement reaction including 1,3O2 molecules and 1,3O2-DMSO adducts and validated it through a simulation of emission intensity change using an ordinary differential equation solver.