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The gene sll1454 (narB) encodes a nitrate reductase in Synechocystis sp. PCC 6803. Deletion of sll1454 was performed by insertion of a gene coding for a neomycin phosphate transferase (npt) in both directions to the sll1454 ORF resulting in two different mutant strains named sll1454::npt direct and sll1454::npt complementary. Both strains lost the ability to grow on nitrate as the only source of nitrogen, but instead grew at the same rate as the wild type if ammonium was supplied. Trace metal replacement experiments revealed that tungsten ions inhibited the nitrate reductase in Synechocystis sp. PCC 6803, as no growth occurred with nitrate as the sole nitrogen source, if molybdenum ions were replaced equimolarly by tungsten ions. Vanadium ions, on the other hand, did not exert any negative effect under the same conditions and neither did the omission of molybdenum, tungsten or vanadium ions in the growth medium. The co-addition of molybdenum ions to cultures containing tungsten ions restored growth to the same rate as in cultures containing only molybdenum ions or none of them. [ABSTRACT FROM AUTHOR]

Since the Nobel prize winning discovery that polyacetylene could act as a semiconductor, there has been tremendous efforts dedicated to understanding and harnessing the unusual properties of π‐conjugated polymers. Much of this research has focused on the preparation of oligoynes and polyynes with well‐defined numbers of repeating alkyne units as models for carbyne. These studies are usually hampered by a structure‐property relationship where the stability of the resulting materials decrease with the incorporation of additional alkyne units. Here, we describe a series of oligoynes, with up to 12 alkyne units, where electron‐rich [Pt(PBu3)2]2+ units are incorporated at the center of the oligoyne backbones which are capped by electron‐poor BF2 formazanate dyes. These compounds exhibit excellent stability and solubility, panchromatic absorption, and redox activity characteristic of their structural components. These traits facilitated thin‐film studies of extended oligoyne materials, where it is shown that incorporating [Pt(PBu3)2]2+ units leads to smoother films, decreased conductivity on the microscale, and increased conductivity on the nanoscale when compared to metal‐free analogs. Remarkably, our oligoynes have superior conductivity compared to the ubiquitous poly(3‐hexylthiophene) semiconductor. [ABSTRACT FROM AUTHOR]

Spectroscopic properties are commonly used in the experimental evaluation of ground‐ and excited‐state aromaticity in expanded porphyrins. Herein, we investigate if the defining photophysical properties still hold for a diverse set of hexaphyrins with varying redox states, topologies, peripheral substitutions, and core‐modifications. By combining TD‐DFT calculations with several aromaticity descriptors and chemical compound space maps, the intricate interplay between structural planarity, aromaticity, and absorption spectra is elucidated. Our results emphasize that the general assumption that antiaromatic porphyrinoids exhibit significantly attenuated absorption bands as compared to aromatic counterparts does not hold even for the unsubstituted hexaphyrin macrocycles. To connect the spectroscopic properties to the hexaphyrins' aromaticity behaviour, we analyzed chemical compound space maps defined by the various aromaticity indices. The intensity of the Q‐band is not well described by the macrocyclic aromaticity. Instead, the degeneracy of the frontier molecular orbitals, the HOMO–LUMO gap, and the |ΔHOMO–ΔLUMO|2 values appear to be better indicators to identify hexaphyrins with enhanced light‐absorbing abilities in the near‐infrared region. Regions with highly planar hexaphyrin structures, both aromatic and antiaromatic, are characterized by an intense B‐band. Hence, we advise using a combination of global and local aromaticity descriptors rooted in different criteria to assess the aromaticity of expanded porphyrins instead of solely relying on the absorption spectra. [ABSTRACT FROM AUTHOR]

The aluminum content of concentrated (27 wt%) sodium chloride solutions could be crucial for large‐scale chlor‐alkali‐based industries applying membrane cell electrolysis. Thus, a facile method which enables a fast and reliable protocol to determine the Al content of these solutions on ppb scale in industrial environments is fundamentally important. It was demonstrated that the increased sensitivity of colorful Al‐ECR (eriochrome cyanine R) complex by the use of a cationic surfactant and specific biological buffers could effectively indicate the Al content in an extended pH interval of a concentrated saline medium under industrial conditions. The dependence of the analytical protocol on pH, temperature, time, wavelength, and the salinity of the medium was investigated. It was shown that the absorbance‐based measurements of the solution should be performed at least 2–4 h after its preparation. By applying the selected two Good's buffers (HEPES: 4‐(2‐hydroxyethyl)‐1‐piperazineethanesulfonic acid, MOPS: 3‐(N‐morpholino)‐propanesulfonic acid) and Tris (tris(hydroxymethyl)aminomethane), 32.8–38.1 % increase in the sensitivity was achieved for saturated NaCl solutions. Moreover, the limits of detection and quantification (LOD, LOQ) were also lowered by 19.0–29.8 %, and the salinity dependence of the calibration was also reduced. [ABSTRACT FROM AUTHOR]

Two π‐extended derivatives of boron‐dipyrromethene (BODIPY) – unsymmetrical benzo[b]‐fused BODIPY 1 and symmetrical naptho[b]‐fused BODIPY 2 – were synthesized. Spectroscopic and photophysical properties of the synthesized fluorescent dyes were investigated in various organic media. Both BODIPY 1 and BODIPY 2 distinguished by bathochromically shifted absorption and emission bands compared to their non‐fused derivatives, while possessing green (526–543 nm) and red (664–708 nm) absorbance and fluorescence, respectively. Spectral characteristics of the investigated fluorescent dyes were found to be weakly depended on solvent polarizability in case of BODIPY 1 and greatly influenced by both solvent polarizability and dipolarity in case of BODIPY 2. Quantum chemical calculations were used to clarify the relationships between geometry/electronic structure and spectral properties/solvatochromic behavior of BODIPY 1 and BODIPY 2. [ABSTRACT FROM AUTHOR]

Ten novel 4-esterchalcones, licochalcone analogues, were strategically synthesized to study the effect of electro-donating or electro-withdrawing substituents in the aryl enone moiety on their pharmacological and photoprotective properties. 4-Esterchalcones had their drug-like character evaluated, which demonstrated positive characteristics for the development of novel drug candidates. In the in vitro antimicrobial evaluation, isovaleryl 4-esterchalcones showed activity against strains of Staphylococcus aureus, Candida albicans and C. tropicalis with minimum inhibitory concentration (MIC) in the range of 2.64-3.32 µmol mL−1, and the isobutyryl 4-esterchalcone 5d (4'-Br) presented antimicrobial activity against all strains tested, with a MIC of 2.74 µmol mL−1. In the UV-Vis study, λmax were observed at 312-327 nm, the UVB range, mainly. The best SPF-UVB results ranged from 18.04 to 21.06, with high εmax values, indicating that 4-esterchalcones have the potential to act as sunscreens. Furthermore, along with the environmental concern, halogenated compounds demonstrated slightly toxic on Artemia salina. [ABSTRACT FROM AUTHOR]

Analysis of purple dyestuff from a tin labeled “1 oz. Cudbear, No. 1 N. F. Powdered”, marketed by the American business S. B. Penick & Company, “Manufacturers of fine drugs and chemicals”, confirmed that the material was indeed a lichen dyestuff. It contains the same major orcein components identified in several other lichen dyes and dyed samples dating from the mid-19th century to today. These dyestuffs were analyzed using several analytical techniques. Fluorescence and fiber optic reflectance spectroscopic data for all the samples were similar. High performance liquid chromatography with diode array detection coupled to mass spectrometry confirmed that this commercial American cudbear was very similar to the samples from the United Kingdom but rather different from the archil-dyed reference yarns from Europe. The significance of the observations is discussed, and chemical structures are proposed for several of the unknown dye components detected in this study.

Designing new validated analytical procedures with a focus on many objectives, such as simplicity, environmental friendliness, analytical effectiveness, and sustainability, has grown to be a top priority in quality control departments. Applying green and white analytical chemistry concepts is no longer a luxury. In this report, two new approaches, Capillary Zone Electrophoresis (CZE) with Photo Diode Array (PDA) detection and derivative ratio spectrophotometric methods, are established and validated for the simultaneous analysis of molnupiravir (MLP) and favipiravir (FAV) in bulk, single dosage forms, and their expected combined dosage forms. For the two drugs, linearity ranges of 5–50 μg/mL and 1–30 μg/mL were achieved using the CZE and spectrophotometric methods, respectively. Both techniques have been validated and used for the estimation of the two medications in lab‐made capsules in accordance with the International Council for Harmonization's (ICH) recommendations. Seven assessment models were used to evaluate the greenness and sustainability of the introduced approaches compared to three previously published HPLC, chemometric, and HPTLC techniques. ChlorTox and BAGI tools are applied for the first time for the evaluation of an analytical procedure. Higher green and sustainable qualities were declared by suggested approaches than by earlier ones. [ABSTRACT FROM AUTHOR]

In this paper, a dispersion of glass beads of different sizes in an ammonium nitrate solution is investigated with the aid of Raman spectroscopy. The signal losses caused by the dispersion are quantified by an additional scattered light measurement and used to correct the measured ammonium nitrate concentration. Each individual glass bead represents an interface at which the excitation laser is deflected from its direction causing distortion in the received Raman signal. It is shown that the scattering losses measured with the scattered light probe correlate with the loss of the Raman signal, which means that the data obtained can be used to correct the measured values. The resulting correction function considers different particle sizes in the range of 2–99 µm as well as ammonium nitrate concentrations of 0–20 wt% and delivers an RMSEP of 1.952 wt%. This correction provides easier process access to dispersions that were previously difficult or impossible to measure. [ABSTRACT FROM AUTHOR]

Deprotonation of our pentadentate N‐Heterocyclic Carbene (NHC) ligand with lithium diisopropylamine in tetrahydrofuran and subsequent salt metathesis with CrCl3THF3 readily forms the complex PhCC4MeCrCl (1), a S=3/2 species in moderate yield. DFT calculations reveal three singly occupied molecular orbitals with π‐backbonding character to the square‐capping framework, UV‐Vis spectroscopy reveals 3 bands ascribed to d‐to‐d transitions, and cyclic voltammetry reveals an irreversible and quazi‐reversible reduction events as well as an irreversible oxidation event. We attempted to exchange the chloride ligand of 1 through salt‐metathesis with lithium phenylacetylide without success, the absence of reactivity is rationalized considering our XRD and DFT results. [ABSTRACT FROM AUTHOR]

Green tea extract (GTE) is a supplement derived from the green tea plant which aids in weight loss along with other innumerable health. New analytical methods for determining GTE via its catechins using a design-assisted spectrophotometric methodologies are provided. The procedures are based on the formation of orange-colored products that are detectable at 473 or 455 nm, respectively, when catechins react with MBTH in the presence of FeCl3 (method I) or K2S2O8 (method II). Critical parameters were optimized using design of experiments (DOE). The absorbance-concentration plots were rectilinear over the ranges 4.0–20.0 or 4.0–40.0 µg cm−3 with limits of detection 0.393 or 0.493 µg cm−3 for methods I & II, respectively. Our methods were applied to pure catechins in GTE, namely (-)-epicatechin and (-)-epigallocatechin gallate. Moreover, the proposed methods were perfectly applied to the analysis of GTE in a commercial tablet. Good agreement between the collected data and those of the reported approach demonstrating that there were no significant variations. According to International Council for Harmonization (ICH) Guidelines, the procedures were validated. [ABSTRACT FROM AUTHOR]

The investigation of reaction mechanisms is a complex task that usually requires the use of several techniques. To obtain as much information as possible on the reaction and any intermediates – possibly invisible to one technique – the combination of techniques is a solution. In this work we present a new setup for combined UV/Vis and NMR spectroscopy and compare it to an established alternative. The presented approach allows a versatile usage of different commercially‐available components like mirrors and fiber bundles as well as different fixed pathlengths according to double transmission or single transmission measurements. While a previous approach is based on a dip‐probe setup for conventional NMR probes, the new one is based on a micro‐Helmholtz coil array (LiquidVoxel™). This makes the use of rectangular cuvettes possible, which ensure well‐defined pathlengths allowing for quantification of species. Additionally, very low quantities of compound can be analyzed due to the microfabrication and small cuvette size used. As proof‐of‐principle this new setup for combined UV/Vis and NMR spectroscopy is used to examine a well‐studied photochromic system of the dithienylethene compound class. A thorough comparison of the pros and cons of the two setups for combined UV/Vis and NMR measurements is performed. [ABSTRACT FROM AUTHOR]

Very recently, N-heterocyclic carbenes (NHCs) have found a wide range of applications in the fields of catalysis and nonlinear optics. Herein, we have employed 1,3-bis-(1(S)-benzyl)-4,5-dihydro-imidazol-based carbene as a reference molecule and substituted one H atom from each CH2 of the benzyl groups in both sides by CH3, NH2, and CF3 to study the thermodynamic and opto-electronic properties of NHCs theoretically. It was observed that the enthalpy (H), Gibb's free energy (G), specific heat capacity (Cv), and entropy (S) increase significantly in the presence of the electron-withdrawing groups compared to the electron-donating groups. The IR active in-plane bending vibrations of the CH (NHC) group are shifted to the higher frequency region for the considered substituted molecules compared to the reference carbene. The analysis of the electronic properties shows that the CH3-substituted carbene is more reactive for catalytic activities compared to other NHCs. The calculated nonlinear optical (NLO) properties reveal that the NH2-substituted NHC has the largest hyperpolarizability value whereas the CH3-substituted NHC has the largest dipole moment and polarizability among all, making them potential candidates for the development of NLO materials. [ABSTRACT FROM AUTHOR]

Analysis of purple dyestuff from a tin labeled "1 oz. Cudbear, No. 1 N. F. Powdered", marketed by the American business S. B. Penick & Company, "Manufacturers of fine drugs and chemicals", confirmed that the material was indeed a lichen dyestuff. It contains the same major orcein components identified in several other lichen dyes and dyed samples dating from the mid-19th century to today. These dyestuffs were analyzed using several analytical techniques. Fluorescence and fiber optic reflectance spectroscopic data for all the samples were similar. High performance liquid chromatography with diode array detection coupled to mass spectrometry confirmed that this commercial American cudbear was very similar to the samples from the United Kingdom but rather different from the archil-dyed reference yarns from Europe. The significance of the observations is discussed, and chemical structures are proposed for several of the unknown dye components detected in this study. [ABSTRACT FROM AUTHOR]

Development of a Membraneless Vanadium Micro Redox Flow Battery (MVMRFB) with an automated closed‐loop control, using micro actuators and micro sensors, is presented for the first‐time during electrolyte preconditioning operation in recirculation mode. The progress of preconditioning is tracked with UV‐vis spectroscopy by 3D printed micro flow cuvettes. Influence of flow rate, reactor internal resistance, and presence of side reactions in the preconditioning process are studied. Optimal flow rate ratio between negative and positive electrolytes is determined and significant performance improvements achieved by operating at lower flow rates are obtained. Influence of reactor internal resistance, which is directly related with the maximum power density, is evaluated demonstrating that operating at a high‐power density can be a source of inefficiency due to the presence of side reactions. Finally, presence of side reactions is evaluated through a dual measurement of electrolytes concentrations in both negative and positive side, and it is demonstrated to be a cause for charge imbalance between the two half‐cells. This work lays a solid foundation for the successful implementation of a charge‐discharge cycle in MVMRFBs operating in recirculation mode. [ABSTRACT FROM AUTHOR]

Physicochemical examinations of very high dilution (UHD) solutions subjected to certain physical factors (such as shaking) are becoming more frequent and are increasingly producing conclusive results. A much less studied phenomenon is the transfer of molecular information (i.e., UHD signals of dilute substances) from one liquid to another without an intermediate liquid phase. The aim of this study was to investigate the possibility of such a transfer of the UHD signal from the UHD solutions to the receiver solution, in particular, if the molecular source used in the donor solutions was the biologically active antibodies to interferon-gamma molecule. We were especially interested in how the transfer of the UHD signal is affected by the time of exposure of the receiver to the donor, the distance between the two, and how the transfer is affected by activation (striking) versus exposure alone. Signal transfer was evaluated by differential measurements of electrical conductivity, ORP, pH, and UV/VIS spectroscopy of the exposed liquid. The results showed that activation strongly influences signal transfer and that this can be compensated to some extent by prolonged direct exposure. In principle, exposure time has a positive effect on signal transfer. Interestingly, the results of different distances between the donor and receiver showed similar changes in the parameters in the range of 0–4 cm, as estimated in this study. While the study mainly confirms the two hypotheses, it also raises a number of new questions and provides clues for further research. [ABSTRACT FROM AUTHOR]

In this work, matrix‐isolation spectroscopy and quantum‐chemical calculations are used together to analyse the structure and properties of weakly bound dimers of the two isomers benzo[a]acridine and benzo[c]acridine. Our measured experimental electronic absorbance spectra agree with simulated spectra calculated for the equilibrium structures of the dimers in gas‐phase, but in contrast, disagree with the simulated spectra calculated for the structures obtained by optimising the experimental solid‐state structures. This highlights the sensitivity of the electronic excitations with respect to the dimer structures. The comparison between the solid‐state and gas‐phase dimers shows how far the intermolecular interactions could change the geometric and electronic structure in a disordered bulk material or at device interfaces, imposing consequences for exciton and charge mobility and other material properties. [ABSTRACT FROM AUTHOR]

A magnetic nano biocomposite was developed by coating the surface of pressed Nigella sativa press cakes agricultural waste with Fe3O4 nanoparticles. The uptake of methylene blue from an aqueous solution was evaluated. pH, adsorbent dosage, interaction time, and other parameters were investigated. Equilibrium, kinetic, and thermodynamic models were analyzed. Desorption studies were performed using various solvents. The uptake efficiency of methylene blue reached 93.22% at pH 11. The adsorbent dosage was determined as 0.6 g/L. The uptake efficiency reached 99.40% at 24 h. Adsorption mechanism is found to be both endothermic and spontaneous. The rate-determining step of adsorption is chemical sorption. The adsorption capacity was 454.55 mg/g. Desorption was performed by ethanol and reached 49.21%. The adsorption performances of the adsorbent were also evaluated by real water samples. Toxic and hazardous reagents were not handled in the preparation of the adsorbent. An environmentally friendly, easily prepared, cheap adsorbent has been developed. [ABSTRACT FROM AUTHOR]

Optical methods such as ultraviolet/visible (UV/Vis) and fluorescence spectroscopy are well-established analytical techniques for in situ water quality monitoring. A broad range of bio-logical and chemical contaminants in different concentration ranges can be detected using these methods. The availability of results in real time allows a quick response to water quality changes. The measuring devices are configured as portable multi-parameter probes. However, their specification and data processing typically cannot be changed by users, or only with difficulties. Therefore, we developed a submersible sensor probe, which combines UV/Vis and fluorescence spectroscopy together with a flexible data processing platform. Due to its modular design in the hardware and software, the sensing system can be modified to the specific application. The dimension of the waterproof enclosure with a diameter of 100 mm permits also its application in groundwater monitoring wells. As a light source for fluorescence spectroscopy, we constructed an LED array that can be equipped with four different LEDs. A miniaturized deuterium–tungsten light source (200–1100 nm) was used for UV/Vis spectroscopy. A miniaturized spectrometer with a spectral range between 225 and 1000 nm permits the detection of complete spectra for both methods. [ABSTRACT FROM AUTHOR]

The goal of this study is to better understand the effect of grinding on the Eg of polypyrrole (PPy)/commercial graphene nanoplatelets (xGnP) composites with varying amounts of xGnP. The Eg for direct transition as a function of the xGnP amount was calculated from the Tauc plot. While the average particle size of the composites decreased between 6% and 30%, there was a slight decrement in the Egs. These values changed between 4.02 to 3.87 eV with the increasing amount of xGnP before grinding, and they reached between 3.97 to 3.88 eV after grinding. Moreover, it was determined that the EU was inversely proportional to Eg. These findings suggest that the PPy/xGnP composites could be suitable for several applications, such as photocatalytic and optoelectronic. [ABSTRACT FROM AUTHOR]

UV/VIS spectroscopy was used in conjunction with a calibration method to determine the mixing ratio of samples of beer-mixed drinks with mineral water (sour Radler beers) from the food service industry. For this purpose, calibration lines were constructed based on absorptions at the two wavelengths 380 nm and 430 nm. To create these calibration lines, blending ratios were prepared from beers from three southwestern German brands and mineral water. The samples of the sour Radler beers were taken from restaurants and bars, which are all located in Baden-Württemberg. It has been shown that the calibration lines can be used to determine mixing ratios with an average deviation of approximately 7% and 9%. Thereby, the calibration line based on the absorption at 430 nm represents a higher accuracy. Using this calibration line, the sour Radler beer samples have percentage ranges of beer of approximately 50% to 90%. This method could serve as a rapid quantitative quality control of the mixing ratios of sour Radler or other beer-mixed drinks. It could be used in breweries for routine control. [ABSTRACT FROM AUTHOR]

The ZnAl1.999Ho0.001O4 phosphor, prepared by the solid-state method, crystallizes in the cubic spinel structure. Morphology and chemical composition homogeneity were determined via Energy Dispersive X-ray and SEM analysis. The (Eg) optical band gap was evaluated from the UV/vis absorption spectrum, confirming direct transition behavior according to Tauc's law. The Urbach energy (Eu) in the ZnAl1.999Ho0.001O4 spinel was higher than that in the ZnAl2O4 spinel, indicating increased disorder and a higher concentration of defects due to Ho3+ ions. The penetration depth (δ(λ)), optical extinction (k(λ)), and refractive index (n(λ)) were assessed across wavelengths (λ). The room temperature absorption spectrum revealed several peaks corresponding to the 4f-4f transitions of Ho3+ ions.

The relationship between extractant stereochemistry and their extraction performance has only poorly been established. In order to address a part of this concern, we investigated the Pu(IV) liquid‐liquid extraction (LLE) by using the N,N‐di‐(2‐ethylhexyl)butyramide (DEHBA), as well as those of its position isomers. DEHBA (ββ‐isomer) and N‐(2‐ethylhexyl)‐N‐(oct‐3‐yl)butyramide (EHOBA or αβ‐isomer) were synthesized as a mixture of stereoisomer or stereoenriched (R,S)‐ and (S,S)‐diastereoisomers, and were all assessed for PuIV LLE. The results showed that both the position and the stereoisomerism of the aliphatic substituents affect PuIV complexation and extraction. We found that Pu extraction is lowered by factor 2 to 4 when the ethyl branching group is closer to the complexing site. UV‐vis spectroscopy showed that this extraction decrease was affected by steric hindrance inducing a deprivation of Pu inner sphere complex. Effect of stereoisomerism is highlighted for branching closer to the complexing site (α‐position). Enantiopure DEHBA stereoisomers provided similar Pu extraction, whereas a slight decrease could be noticed for the more cluttered stereoenriched (αβ)‐isomers, which was also concomitant with a smaller population of inner sphere complex. In contrast, the stereoisomers mixture led to a strong decrease of Pu extraction because of an antagonistic association in the mixed complexes. [ABSTRACT FROM AUTHOR]

The synthesis of three novel imidazolyl‐substituted sulfur‐containing heteroacenes is reported. These heteroacenes consisting of annelated benzo‐ and naphthothiophenes serve as precursors for the generation of open‐shell quinoid heteroacenes by oxidation with alkaline ferric cyanide. Spectroscopic and computational experiments support the formation of reactive open‐shell quinoids, which, however, quickly produce paramagnetic polymeric material. [ABSTRACT FROM AUTHOR]

Obtaining understanding of a photochemical reaction relies on the observation, identification and quantification of the compounds involved. The photochemical properties of the individual components are of particular importance, and their determination, however, is not always trivial. This is also true for the quantitative measure on the ability to absorb light, the extinction coefficient εi if more than one species i is present and two or more species absorb light of the same wavelength. In this work, it is demonstrated how pure component spectra can be obtained with a simple combination of successive and repeated ex situ illumination, UV/Vis and NMR spectroscopy. From the complementary information accessible, the wavelength-dependent extinction coefficients of all species can be calculated yielding the pure component spectra. A comparison with published data shows excellent agreement and thus proves that this approach is highly reliable. [ABSTRACT FROM AUTHOR]

Fruit juices, and especially lime juice, belong to the most targeted food commodities for fraud. Therefore, reliable and cost-effective analytical methodologies need to be developed to guarantee lime juice authenticity and quality. The manifestation of machine learning techniques (MLT) has paved the way for fast and reliable processing and analysis of food and juice data for more effective use of inexpensive, readily available, and easy-to-use equipment such as UV/Vis spectrometers for quality control. The study aimed to investigate UV/Vis spectrometry and MLT to detect at least 10% of water, acid, and sugar added to lime juice. For this purpose, 26 lime samples, including Mexican and Persian lime, were collected from the orchards of four main lime-cultivated areas in Iran to prepare pure lime juice samples (as authentic samples). To investigate adulterated lime juice, four types of treatment were defined by adding acid, sugar, a mix of acid and sugar solution, and water at different volume proportions (10, 20, 30, 40, and 50 % v/v) to pure lime juice samples. Each treatment was repeated eight times. The absorption rate of different adulterated and pure lime juice samples was measured at different wavelengths in the 210-550 nm range. The evaluation results of different MLTs showed that the accuracy of separating samples using absorption data by decision tree (DT), k-nearest neighbor (k-NN), random forest (RF), multilayer perceptron (MLP), and support vector machine (SVM) were 75%, 79%, 80%, 87%, and 92%, respectively. SVM had the highest level of accuracy in separating adulterated lime juice samples. Also, this model's performance criteria (sensitivity and F-score) were higher than other models for identifying adulterated samples using absorption data. This is the first time that the common adulterations in lime juice were identified by rapid and accessible screening methods using UV/Vis spectroscopy and MLT with high accuracy, precision, and sensitivity. [ABSTRACT FROM AUTHOR]

Nickel phthalocyanine complex containing 3-methoxybenzoic acid groups was acquired and specified by way of Fourier Transform Infrared, NMR and UV-Visble spectroscopy procedures. Interaction of PcNi with the DNA molecule was examined via electronic absorption spectra, fluorescence spectra, melting point, viscosity, and the electrophoresis technics, respectively. The interaction activity of PcNi against the DNA was examined by way of absorption spectra titrations and the fluorescence spectra, farther by conducting melting point, viscosity procedures in the buffer of a pH 7.02. The obtained outcomes from these methods demonstrated that PcNi indicated substantial binding affinity to the DNA via intercalating by Kb of 1.31 x 106 m-1. Further, the interacting activity of PcNi on the DNA was analyzed by which electrophoresis technique and this procedure indicated that PcNi complex exhibits strong binding affinity on the DNA. [ABSTRACT FROM AUTHOR]

With the goal to better process the monitoring of occurring fouling, a backscatter probe was developed to perform in-line measurements in a half-shell reactor during the reaction of N-vinylpyrrolidone (NVP) to polyvinylpyrrolidone (PVP). The measurement technique detects the changes of bands in the UV range, which allows a direct correlation with the concentration. Thus, the measured absorbance signal allows a conclusion on the accumulation of fouling in the reactor and on changes in the conversion at the measurement location.

Abstract The synthesis of three novel imidazolyl‐substituted sulfur‐containing heteroacenes is reported. These heteroacenes consisting of annelated benzo‐ and naphthothiophenes serve as precursors for the generation of open‐shell quinoid heteroacenes by oxidation with alkaline ferric cyanide. Spectroscopic and computational experiments support the formation of reactive open‐shell quinoids, which, however, quickly produce paramagnetic polymeric material.

The absorption and emission properties of a series of 44 aromatic molecules have been investigated in Time Dependent Density Functional Theory (TDDFT) using different exchange‐correlation functionals. Solvent effects have been included within linear response (LR) and state specific (SS) polarisable continuum model (PCM). The comparison with experimental UV‐Vis data showed reasonable agreement for all the aromatic molecules when ωB97XD with SS‐PCM is used. In particular, we found an accurate linear correlation between experimental and theoretical results which is revealed in an equation for absorption and another equation for emission derived from a linear fitting between theoretical and experimental data. Through these linear equations we propose a simple, pragmatic and effective approach able to describe and predict the absorption and the emission of aromatic molecules with a reasonable computational cost. [ABSTRACT FROM AUTHOR]

The pharmacopoeial test method "Intrinsic Dissolution" (Ph.Eur. 2.9.29) is used to study the rate of dissolution for powders of active pharmaceutical ingredients normalized by the surface area. Therefore, powders are compacted into a special metal die holder, which is immersed into a dissolution vessel of the dissolution test apparatus (described in Ph.Eur. 2.9.3). However, in some cases, the test cannot be performed because the compacted powder would not stay in the die holder when in contact with the dissolution medium. In this study, we investigated the removable adhesive gum (RAG) as an alternative to the official die holder. Intrinsic dissolution tests were carried out to exemplify the use of the RAG for this purpose. As model substances, acyclovir and its co-crystal with glutaric acid were used. The RAG was validated for compatibility, release of extractables, unspecific adsorption and the ability to block drug release through the covered surfaces. The results showed that the RAG leaked no unwanted substances, showed no adsorption of acyclovir and blocked its release from covered surfaces. The intrinsic dissolution tests revealed, as expected, a constant release of drug with a small standard deviation between replicates. It was possible to distinguish the acyclovir release from the co-crystal and from the pure drug compound. In conclusion, the findings of this study suggest to consider removable adhesive gum as an easy-to-use and inexpensive alternative to the compendial die holder in intrinsic dissolution tests. [Display omitted] [ABSTRACT FROM AUTHOR]

Physicochemical investigations of (UHD) solutions subjected to certain physical factors (like shaking) are becoming more frequent and increasingly yielding convincing results. A much less studied phenomenon is the transfer of molecular information (UHD signals) from one fluid to another without an intermediate liquid phase. The purpose of this study was to investigate the possibility of such a UHD signal transfer from UHD solutions into the receiver fluid, especially when the molecular source used in solutions was a biologically active molecule of antibodies to interferon-gamma. We used physicochemical measurements and UV spectroscopy for this purpose. The results of this large pilot study confirm the possibility of such a transfer and a rough similarity to the original UHD signal donors, the weaker signal detection relative to the original donor fluids, and that exposure time improves the effect. [ABSTRACT FROM AUTHOR]

The expansion of d‐orbitals as a result of metal‐ligand bond covalence, the so‐called nephelauxetic effect, is a well‐established concept of coordination chemistry, yet its importance for the design of new photoactive complexes based on first‐row transition metals is only beginning to be recognized. Until recently, much focus has been on optimizing the ligand field strength, coordination geometries, and molecular rigidity, but now it becomes evident that the nephelauxetic effect can be a game changer regarding the photophysical properties of 3d metal complexes in solution at room temperature. In CrIII and MnIV complexes with the d3 valence electron configuration, the nephelauxetic effect was exploited to shift the well‐known ruby‐like red luminescence to the near‐infrared spectral region. In FeII and CoIII complexes with the low‐spin d6 electron configuration, charge‐transfer excited states were stabilized with respect to detrimental metal‐centered excited states, to improve their properties and to enhance their application potential. In isoelectronic (3d6) isocyanide complexes of Cr0 and MnI, the nephelauxetic effect is likely at play as well, enabling luminescence and other favorable photoreactivity. This minireview illustrates the broad applicability of the nephelauxetic effect in tailoring the photophysical and photochemical properties of new coordination compounds made from abundant first‐row transition metals. [ABSTRACT FROM AUTHOR]

A series of thienoindolizine structural isomers have been synthesized in a one‐pot, two‐step procedure starting from easily accessible gem‐difluoroalkene functionalized bromothiophenes. The developed method gives easy access to a range of thienoindolizine products containing thieno[3,2‐g]‐, thieno[3,4‐g]‐ and thieno[2,3‐g]indolizine core structures. The described synthesis strategy consists of a base mediated, transition metal free nucleophilic substitution of fluorine atoms by nitrogen containing heterocycles followed by a Pd catalyzed intramolecular cyclization. A series of 22 final product examples has been obtained with yields ranging from 29 % to 95 %. UV/Vis absorption, fluorescence spectroscopy, fluorescence lifetime measurements and cyclic voltammetry were carried out with selected final products to evaluate structural effects on photophysical and electrochemical properties. (TD)DFT and NICS calculations were performed to provide insight into the electronic properties of the four core molecular structures. [ABSTRACT FROM AUTHOR]

The interaction of a number of gold(III) complexes: Au(phen)X2+, Au(bipy)X2+ (X=Cl, OH, phen=1,10‐phenanthroline, bipy=2,2'‐bipyridile), Au(en)23+ and Au(dien)Cl2+ with anions of thiol‐containing acids (thiomalate, cysteine and glutathione) in an aqueous solution at pH 2.0 and 7.4, CNaCl=0.2 M was studied. In all cases, the products of gold(III) reduction were highly stable gold(I) thiolate complexes: polymeric Aum(RS)n or monomeric Au(RS)2, depending on the conditions. For bipy and phen complexes, the processes were fast and usually completed in less than 1 minute. For the complex with dien, the stage of inner‐sphere reduction was the slowest among the complexes under consideration. For this complex, at pH 7.4 and with a large excess of glutathione, the formation of a relatively long‐lived gold(III) complex was observed, which, according to MS data, has the composition Au(GSH)45–. At ordinary temperature, it decomposes by about 90 % in 20 hours. For other thiols, similar complexes are also formed, but the rate of their decomposition is about 10 times higher. [ABSTRACT FROM AUTHOR]

Mathematical models for the concentration‐, temperature‐ and solvent‐dependent analysis of self‐assembly equilibria are derived for the most simple case of dimer formation, to highlight the assumptions these models and the thus determined thermodynamic parameters are based on. The three models were applied to UV/Vis absorption data for the dimerization of a highly dipolar merocyanine dye in 1,4‐dioxane. Isothermal titration calorimetry (ITC) dilution experiments were performed as an independent reference technique. While the concentration‐dependent analysis is according to our studies the most reliable method, also the less time‐consuming temperature‐dependent evaluation can give accurate results in the present example, despite small thermochromic effects. In contrast, the strong negative solvatochromism of the merocyanine tampers with the results from the solvent‐dependent evaluation. Even though the studies presented in this work are limited to the monomer‐dimer equilibrium of a dipolar dye, the basic principles can be transferred to other chromophores and different self‐assembly models, including those for supramolecular polymerization. [ABSTRACT FROM AUTHOR]

Nanodiamonds (NDs) are advantageous for targeted cancer treatment with payload medications due to their good biocompatibility. Herein, a nanodrug delivery system, ND‐fucoxanthin (ND‐FX), was generated by combining FX and acyl chloride‐functionalized NDs, which were created by dispersing and surface‐modifying NDs. The structure and characteristics of NDs were examined via X‐ray diffraction, transmission electron microscopy, and Fourier transform infrared spectroscopy. Subsequently, the drug‐loading and ‐release rates of ND‐FX under different pH conditions were calculated using ultraviolet‐visible spectrophotometeric analysis. The drug‐loading rate of the ND‐FX system was 13.17 %; release rate of FX at pH 7.4 and 6.5 was 27.79 % and 54.65 %, respectively; and cumulative release rate of ND‐FX reached 79.98 % over a release duration of 72 h at pH 5.0. Meanwhile, in vitro cytotoxicology experiments demonstrated that ND‐FX effectively inhibited the activity of HeLa and HepG2 cells. These results demonstrate the potential value of NDs in the field of nanodrug delivery applications. [ABSTRACT FROM AUTHOR]

A new series of 4H-1,3-benzothiazine dyes were prepared and fully characterized in an aqueous medium. Benzothiazine salts were synthesized either through the classical synthetic pathway using Buchwald–Hartwig amination or through economical and environmentally friendly electrochemical synthesis. The latest synthetic approach employs successful electrochemical intramolecular dehydrogenative cyclization of N-benzylbenzenecarbothioamides to form 4H-1,3-benzothiazines. 4H-1,3-Benzothiazines were evaluated as novel DNA/RNA probes. Through the use of several methods such as UV/vis spectrophotometric titrations, circular dichroism and thermal melting experiments, the binding of four benzothiazine-based molecules to polynucleotides was examined. Compounds 1 and 2 acted as DNA/RNA groove binders, thus suggesting the potential of these compounds as novel DNA/RNA probes. This is a proof-of-concept study and will be expanded to include SAR/QSAR studies. [ABSTRACT FROM AUTHOR]

Several different evaluation methods (EM) to obtain the band gap energy (Eg) of semiconductors via UV/Vis diffuse reflectance spectroscopy (DRS) are used in literature and no clear consensus which EM to use is established. By using P25 as a model semiconductor, evaluating 32 literature sources and our own experiments, we show that the determined Eg energy is heavily influenced by the EM (differences in Eg of up to 0.87 eV). For P25 loaded with CuO even contradictive effects of metal loading on the Eg are observed using different EM. Different phase compositions of TiO2 are also shown to yield EM‐dependent results. This paper thus comprehensively investigates the most common EM on different relevant photocatalyst material classes, illustrates their mathematical and graphical determination, gives recommendations which method to use based on a quantitative indicator and illustrates common pitfalls in determining Eg via UV/Vis DRS. [ABSTRACT FROM AUTHOR]

Due to their excellent prospects in biological applications, Schiff bases and their complexes are a source of continuing interest. The present study examines the formation of four cobalt(II) complexes with the reduced Schiff base N-(2-hydroxybenzyl)phenylalanine (PhAlaSal) in alkaline aqueous solution by pH-metry. UV–Vis and ESI–MS studies confirmed the model of proposed species. Kinetic analysis indicated that the single- and bi-ligand cobalt(II) complexes transitioned from octahedral to tetrahedral structures. The Schiff base and its complexes detected under physiological pH were tested for antimicrobial abilities and compared with analogous structures of the Schiff base derivative, N-(2-hydroxybenzyl)alanine (AlaSal). The ability of these structures to influence cell growth was tested on L929 mouse fibroblasts and on cervix and gastric adenocarcinoma cancer cell lines. N-(2-hydroxybenzyl)phenylalanine demonstrates greater antimicrobial efficacy than N-(2-hydroxybenzyl)alanine but also higher cytotoxicity; however, it is nonetheless effective against cancer cells. In turn, AlaSal demonstrates low cytotoxicity for fibroblasts and high cytotoxicity for gastric adenocarcinoma epithelial cells at bacteriostatic concentration for Helicobacter pylori and Candida strains. The presence of these microorganisms in the gastric milieu supports the development of gastritis and gastric cancer; AlaSal therapy may be simultaneously effective against both. Due to their cytotoxicity, Schiff base complexes are not suitable for use against fungal and bacterial infections, but may effectively prevent cancer cell growth. Data availability: Data will be made available on request.

Folic acid (FA) is used as target drug delivery for cancer cells by adding to copper/chitosan nanocomposite (Cu/CNC) to form FA-Cu-CS complex. Chitosan is a promising polymeric that has received a lot of attention recently. Chitosan nanoparticles have wide applications as a nanocarrier for different organic and inorganic substances. In the present study, chitosan nanoparticles (CNP), Cu/CNC, and FA-Cu-CS had been prepared and characterized. Structural, morphological, optical and anticancer activities of the nanoparticles were studied. X-ray diffraction study showed the formation of CNP, Cu/CNC, and FA-Cu-CS. FE-SEM showed the CNPs have spherical shape. While, FE-SEM image of Cu/CNC has aggregated and semi-spherical shapes, but the image of FA-Cu-CS showed aggregated, agglomerated, and irregular shapes. FTIR analysis resulted peak at 1026.13 cm–1 refer to the CNPs bonded with folic acid. UV/VIS spectroscopy showed absorbance peak at 530 nm due to presence of FA-Cu-CS. Moreover, anticancer activity of CNPs, Cu/CNC and FA-Cu-CS was tested by MTT assay against fibroblast, MCF-7 and ovarian cancer, then it was stained by DAPI to show the morphology of nucleus. FA-Cu-CS has higher cytotoxicity from other nanoparticles which was 54%, 65% and 83% against fibroblast, MCF-7 and ovarian cancer, respectively at concentration of 0.175 μL/mL. To our knowledge, there is no report on enhancing the anticancer activity of copper/chitosan nanocomposite by conjugated with folic acid and comparison of anticancer activity among CNPs, Cu/CNC and FA-Cu-CS.

This study reports the evaluation of 2-acetylpyridine based chalcone structure as a useful sensing material for Hg2+ ion detection by the means of UV-visible spectroscopy. In this context, firstly, the most common twenty metal ions were treated by the chalcone structure which was synthesized from 2-acetylpyridine and 4-diphenylaminobenzaldehyde according to the known procedures. As result, the studied chalcone compound exhibited good sensing activity towards Hg2+ ion in acetonitrile/water medium with significant red-shift phenomenon. In addition, some photophysical/electronic parameters of the chalcone and its Hg2+ complex were determined experimentally and theoretically. B3LYP, PBE0 methods and SVP, TVZP, and TVZPP basis sets were used for theoretical calculations in acetonitrile media. Finally, experimental results were explained and the proposed sensing mechanism was supported via density functional theory (DFT) outputs.

Protein crystallization is nowadays performed at the micro to macro scale in academia and industry, being particularly interesting for pharmaceutical applications. Protein crystallization offers an attractive alternative to chromatography as a downstream processing step in the biotechnology industry, but also in the food and chemical industries. Monitoring of the protein crystallization process is required to understand the crystal growth mechanism and to obtain the information necessary for efficient process control, which needs to comply with the critical quality attributes of the product. Since a wide range of monitoring techniques have already been developed and established, this review focuses on the recent advances of selected techniques in monitoring protein crystallization processes such as the focused beam reflectance method (FBRM), and machine learning-based image analysis for solid-phase monitoring, as well as the spectroscopic methods for liquid-phase monitoring, such as attenuated total reflectance Fourier transform infrared (ATR-FTIR) and UV/Vis spectroscopy. [ABSTRACT FROM AUTHOR]

Possible routes for intra‐cluster bond formation (ICBF) in protonated serine dimers have been studied. We found no evidence of ICBF following low energy collision‐induced dissociation (in correspondence with previous works), however, we do observe clear evidence for ICBF following photon absorption in the 4.6–14 eV range. Moreover, the comparison of photon‐induced dissociation measurements of the protonated serine dimer to those of a protonated serine dipeptide provides evidence that ICBF, in this case, involves peptide bond formation (PBF). The experimental results are supported by ab initio molecular dynamics and exploration of several excited state potential energy surfaces, unraveling a pathway for PBF following photon absorption. The combination of experiments and theory provides insight into the PBF mechanisms in clusters of amino acids, and reveals the importance of electronic excited states reached upon UV/VUV light excitation. [ABSTRACT FROM AUTHOR]

In this work, we have developed a real-time UV/VIS spectroscopy method using a broadband Xenon Arc lamp to detect photocatalytic reactions in real time. A CMOS camera was used instead of an output slit to capture all spectral information simultaneously, which can enable a real-time detection of the UV/VIS absorption of the analytes within a single frame of the camera. To verify real-time spectroscopy, a wavelength calibration process was performed using three laser line filters and a didymium glass filter sample. To demonstrate that this real-time spectroscopic setup can be used for rapid measurements, MB samples were used to observe the real-time photocatalytic degradation of MB by TiO2 nanoparticles. For real-time measurement, four samples with different TiO2 nanoparticle quantities showed different photocatalytic degradation mechanisms. By plotting the spectra every 20 ms, the series of spectra clearly showed the degradation of MB in real time. [ABSTRACT FROM AUTHOR]

Photoreceptors containing the light‐oxygen‐voltage (LOV) domain elicit biological responses upon excitation of their flavin mononucleotide (FMN) chromophore by blue light. The mechanism and kinetics of dark‐state recovery are not well understood. Here we incorporated the non‐canonical amino acid p‐cyanophenylalanine (CNF) by genetic code expansion technology at 45 positions of the bacterial transcription factor EL222. Screening of light‐induced changes in infrared (IR) absorption frequency, electric field and hydration of the nitrile groups identified residues CNF31 and CNF35 as reporters of monomer/oligomer and caged/decaged equilibria, respectively. Time‐resolved multi‐probe UV/visible and IR spectroscopy experiments of the lit‐to‐dark transition revealed four dynamical events. Predominantly, rearrangements around the A'α helix interface (CNF31 and CNF35) precede FMN‐cysteinyl adduct scission, folding of α‐helices (amide bands), and relaxation of residue CNF151. This study illustrates the importance of characterizing all parts of a protein and suggests a key role for the N‐terminal A'α extension of the LOV domain in controlling EL222 photocycle length. [ABSTRACT FROM AUTHOR]

The accurate measurement of redox potentials of small molecules is a relatively straightforward task using electrochemical methods such as cyclic voltammetry. However, proteins, in most cases, are not amenable to the same approach due to slow heterogeneous electron transfer and the possibility of denaturing at the electrode surface. This necessitates the use of small molecular weight redox mediators to facilitate electron transfer. This leads to spectroelectrochemical techniques where the applied electrochemical potential is coupled to a spectroscopic signal of the protein. Traditionally this is done at different applied (fixed) potentials akin to an electrochemical titration, but the time required for electrochemical equilibrium to be established, and its consistent application, are major sources of experimental error. Here we have utilised a continuously scanning potential synchronised with time‐resolved UV‐vis spectroscopy to provide an automated approach that can be used to measure protein redox potentials accurately in an expedient manner. The test cases are the heme proteins cytochrome c and myoglobin. The scope and limitations of the method are discussed. [ABSTRACT FROM AUTHOR]

The applications of surfactants in various fields are gaining more attention, which makes full characterization of surfactants of growing interest. It is fundamental to measure the critical micelle concentration (CMC) as a parameter for characterizing surfactants. Spectroscopic methods for determination of CMC are more common, easier to perform, and in certain applications more accurate. In this review, different spectroscopic techniques and methods used for determination of CMC are discussed. These methods include direct UV/VIS Spectroscopy, which studies liquid surface curvature in thin wells using vertical detecting light beam with the wavelength set at 900 nm. The indirect UV/VIS Spectroscopic methods include using surface plasmon resonance or surface-enhanced Raman scattering of metal nanoparticles. Direct spectrofluorometric methods measure CMC based on the intrinsic fluorescence of the tested surfactants, and it was reserved for surfactants with intrinsic fluorescence such as Triton-X100. Indirect spectrofluorometric methods include measuring the change in fluorescence intensity, spectral shape, lifetime, polarization, or the solvatochromic shift of surfactant-dye solution. Other spectroscopic methods have been reported such as X-ray diffraction, nuclear magnetic resonance spectroscopy and small-angle neutron scattering. This review article discusses the spectroscopic methods developed for CMC determination with emphasis on the principle, applications, advantages, and limitations of each method. [ABSTRACT FROM AUTHOR]

With the goal to better process the monitoring of occurring fouling, a backscatter probe was developed to perform in-line measurements in a half-shell reactor during the reaction of N-vinylpyrrolidone (NVP) to polyvinylpyrrolidone (PVP). The measurement technique detects the changes of bands in the UV range, which allows a direct correlation with the concentration. Thus, the measured absorbance signal allows a conclusion on the accumulation of fouling in the reactor and on changes in the conversion at the measurement location. [ABSTRACT FROM AUTHOR]