UV Absorption Spectra Research Articles

Molecular, spectroscopic and thermochemical characterization of C2Cl3, C2F3 and C2Br3 radicals and related species.

This work reports a detailed theoretical study of the molecular parameters, harmonic vibrational frequencies, UV absorption spectra and standard enthalpies of formation for the radicals C2X3 (with X = F, Cl and Br) and a comparison with the corresponding determinations for the rest of the members of the family C2X n (with n = 2-4). Molecular properties were calculated using different levels of theory: density functional theory employing the B3LYP, X3LYP, BMK, M06-2X and M08-HX functionals combined with the basis sets 6-311++G(3df,3pd) and aug-cc-pVTZ, and the ab initio composite models G3B3 and G4. Structural and spectroscopic characterization of the C2F3, C2Cl3 and C2Br3 radicals, along with the estimation of the enthalpies of formation of C2F3 and C2Cl3, were derived here for the first time, to our knowledge. In particular, values of -220.9 ± 2.9, 230.8 ± 3.8 and 375.4 ± 5.9 kJ mol-1 were computed for enthalpies of formation of C2F3, C2Cl3 and C2Br3, respectively. Additionally, enthalpies of formation for related closed-shell molecules were obtained with less uncertainty compared to those found in the literature. The recommended values of -669.6 ± 3.8, -23.0 ± 4.6 and 155.3 ± 5.0 kJ mol-1 were derived for C2F4, C2Cl4 and C2Br4, while corresponding values of 0.6 ± 6.3, 228.1 ± 2.1 and 319.6 ± 5.4 kJ mol-1 were estimated for C2F2, C2Cl2 and C2Br2, respectively.

A Turn‐On Fluorescence Probe Based on a New Salamo‐Co (II) Coordination Polymer for Tyrosine Detection and Its Application in Water Samples

ABSTRACTA novel salamo‐Co (II) coordination polymer probe CP was synthesized firstly, and its crystal structure, [Co3(L)2(PTA)(H2O)2]n·4nDMF, was determined by X‐ray diffraction analysis. The probe has a rare aggregation‐induced luminescence enhancement (AIEE) effect. When applied to amino acid detection, it was found to have a high selective recognition of tyrosine. With the increase of tyrosine, the fluorescent strength of the probe was enhanced in a short period of time. In addition, the binding ratio of probe to Tyr was determined by fluorescence titration experiment, and the detection limit LOD of probe CP for Tyr was calculated to be 2.57 × 10−9 M, and the binding constant Ka was 2.96 × 105 M−1. According to UV absorption spectrum, FT‐IR spectra, ESI mass spectrometry, and DFT calculation, it was speculated that Tyr can bind to the probe after adding Tyr into the probe solution, triggering FRET and ICT effects, resulting in increased fluorescence intensity and blue shift, and finally achieving the specific recognition of tyrosine by probe CP. Finally, the practical application of probe CP was studied. Through strip test and real water sample test, it was found that the probe can be used for qualitative and quantitative analysis of tyrosine.

The substantial generation of photochemically produced reactive intermediates (PPRIs) in algae-type zones from one large shallow lake promoted the removal of organic pollutants

Photochemically produced reactive intermediates (PPRIs) are ubiquitously present in aquatic systems and hold significant importance in biogeochemical cycles. The photochemical reaction of dissolved organic matter (DOM), known as photosensitizers upon irradiation, is the main pathway for PPRIs generation. However, the PPRIs produced by algal-derived organic matter (ADOM) and their environmental effects remains elusive. This study confirmed that substantial PPRIs were generated by ADOM in the algal-derived areas. UV absorption spectra, fluorescence spectra and Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) were then indicated a significant correlation between the molecular weight of DOM and the quantum yield of PPRIs, with lower molecular weight of DOM exhibiting a higher potential for PPRIs generation. Orthogonal partial least squares (OPLS) were used to build novel multivariate predictive models for indicating the PPRIs production in algae-type zone. Also, the higher concentrations of PPRIs could significantly removal different kinds of organic pollutants, such as bisphenol A (BPA), sulfadiazine (SDZ) and 17α-ethinylestradiol (EE2). Quenching experiments further elucidated that 3DOM⁎ was the key specie for pollutants degradation, serving as the precursor to generate a series of PPRIs. This study highlighted the importance of PPRIs generated from ADOM in the natural attenuation of pollutants and provided a new insight for understanding the self-purification in aquatic system.

Binding characteristics of the major kratom alkaloid, mitragynine, towards serum albumin: Spectroscopic, calorimetric, microscopic, and computational investigations

Mitragynine (MTG) is a prominent indole alkaloid that is present abundantly in Mitragyna speciosa, commonly referred to as kratom. MTG has garnered significant attention due to its selective agonistic characteristics towards opioid receptors and related analgesic effects. In the circulatory system, the in vivo efficacy of MTG is dictated by its interaction with plasma proteins, primarily human serum albumin (HSA). In the present study, we utilized a broad methodology that included spectroscopic, calorimetric, microscopic, and in silico approaches to characterize the interaction between MTG and HSA. Alterations in the UV absorption spectrum of HSA by the presence of MTG demonstrated a ground-state complexation between the protein and the ligand. The Ka values obtained for the MTG–HSA interaction were in the range 103–104 M−1 based on analysis of fluorescence and ITC data, respectively, indicating an intermediate binding affinity. The binding reaction was thermodynamically favorable as revealed by ΔH, ΔS, and ΔG values of −16.42 kJ mol−1, 39.97 J mol−1 K−1, and −28.34 kJ mol−1, respectively. Furthermore, CD spectroscopy results suggested MTG binding induced minimal effects on the structural integrity of HSA, supported by computational methods. Changes in the dimensions of HSA particles due to aggregation, as observed using atomic force microscopy in the presence of MTG. Competitive drug displacement results seemingly suggested site III of HSA located at subdomain IB as the preferred binding site of MTG, but were in inconclusive. However, docking results showed the clear preference of MTG to bind to site III, facilitated by hydrophobic (alkyl and pi-alkyl) and van der Waals forces, together with carbon hydrogen bonds. Additionally, the MTG–HSA complexation was demonstrated to be stable based on molecular dynamics analysis. The outcomes of this study shed light on the therapeutic potential of MTG and can help in the design of more effective derivatives of the compound.

Three spectrophotometric quantitative analysis of bisoprolol fumarate and telmisartan in fixed-dose combination utilizing ratio spectra manipulation methods

Hypertension is a chronic condition with multiple drug regimens. Limiting these medicines is critical to patient compliance. Therefore, bisoprolol and telmisartan were recently developed in a fixed-dose combination to control blood pressure. The UV absorption spectra of bisoprolol and telmisartan overlapped significantly. Thus, three spectrophotometric methods have been developed for simultaneous determination of bisoprolol and telmisartan without prior separation. Method A is ratio difference of ratio spectra (RD), which measures the amplitude difference between (210–224) nm for bisoprolol and between (255–365) nm for telmisartan. Method B, the first derivative of ratio spectra (1DD), measures amplitude signals at 232 and 243 nm for bisoprolol and telmisartan, respectively. Method C is the mean centering of ratio spectra (MC), which measures the mean-centered ratio spectra's values at 223 nm for bisoprolol and 245 nm for telmisartan. The applied methods showed good linearity 2–20 µg/mL for bisoprolol, 4–32 µg/mL for telmisartan, with sufficient accuracy and precision. The methods were sensitive, with LOD values of 0.243 µg/mL and 0.596 µg/mL in RD method, 0.313 µg/mL and 0.914 µg/mL in 1DD method, and 0.406 and 0.707 µg/mL in MC method for bisoprolol and telmisartan, respectively, the methods were validated per ICH criteria. The novel methods are precise and accurate and can be used for routine analysis and quality control of bisoprolol and telmisartan in pure and dosage form. Furthermore, the greenness of the approaches was evaluated using Analytical Greenness assessment (AGREE), and the suggested method received a high greenness score.

Photoprotective properties of four structure propolis from Heterotrigona itama stingless beehive: Fractionation, bioactivity analysis, and chemical profiling

Heterotrigona itama stingless bee propolis extract is known for its diverse bioactive compounds, making it a potential natural shield against UV radiation. This research assesses the photoprotective potential of crude ethanol extract from H. itama propolis collected from four structures (involucrum, pillar, pot, and entrance) of five bee hives (H1-H5), totalling 20 samples. Initially, the samples underwent testing for SPF value and UV absorption spectra. The crude ethanol extract (E) from the involucrum (H4) with the highest SPF value and broadest spectrum was selected for fractionation using hexane and water. Subsequently, the extract (E) and its hexane (H) and water (W) fractions were subjected to SPF analysis, UVA/UVB absorption assessment, determination of total phenolic and flavonoid content, free radical scavenging capacity, anti-collagenase effects, and cytotoxicity assessment. Additionally, LC-MS/MS analysis was performed to identify chemical constituents in the active fraction (W). The extract E demonstrated an SPF of 8.23 ± 0.09 and UV absorption. Notably, its fraction W exhibited the highest SPF (16.55 ± 0.24) at 100 μg/mL, surpassing the H fraction (SPF 5.7 ± 0.45). Phenolic content was highest in the H fraction (388.95 ± 4.54 mg/g GAE DW), followed by the W fraction (286.76 ± 6.48 mg/g GAE DW) and crude E (91.83 ± 4.12 mg/g GAE DW) from the involucrum. Regarding flavonoids, the fraction W led with 79.82 ± 6.21 mg/g QE DW, followed by the H fraction (45.56 ± 0.05 mg/g QE DW) and E (34.57 ± 1.11 mg/g QE DW). The extract E also exhibited modest DPPH scavenging (EC50 = 120 μg/mL), while the H fraction demonstrated stronger activity (EC50 = 4.37 μg/mL), and the W fraction displayed moderate effects (EC50 = 17.55 μg/mL). Notably, the W fraction showed remarkable anti-collagenase activity, outperforming the positive control, EG. HaCaT cell cytotoxicity revealed that the extract E was cytotoxic, whereas the H and W fractions showed no toxicity. LC-MS/MS analysis identified bioactive flavonoids (e.g., pratensein, quercetin) in the W fraction. These findings highlight the superior photoprotective properties of the water fraction from the involucrum of H. itama stingless bee propolis extract, suggesting its potential as a natural and effective ingredient for sunscreen and skincare formulations.

Simultaneous spectrophotometric and chromatographic determination of Ketorolac and Dexamethasone: Overall assessment regarding environmental Impact, Practicality, and functionality principles

Determination of a drug combination that contains a minor component that is also a poorly UV absorbing analyte represents greet challenges in drug analysis. A fixed-dose ophthalmic combination of ketorolac tromethamine (KET) and dexamethasone sodium phosphate (DEX) (in the ratio of 5:1) is used to relieve post-surgical inflammation and seasonal allergic conjunctivitis due to their analgesic and anti-inflammatory activity. Five spectrophotometric methods and a reversed phase chromatographic separation method were developed and validated for simultaneous determination of both drugs in lab-prepared eye drops. Direct spectrophotometric determination of KET (the major, highly UV absorbing analyte) was achieved from the zero-order UV absorption spectra at 323 nm while DEX (which is the minor, poorly UV absorbing analyte) was quantified after applying several spectrophotometric methods. Either fundamental zero-order spectra or ratio spectra were used, and measurements were done at either single or dual wavelengths. The developed methods were: isosbestic point method, absorption factor method, dual wavelength method, ratio difference UV spectrophotometric method, and simultaneous equation method. The developed spectrophotometric methods determine KET in the linearity range of 2.0–12.0 μg/mL and DEX in the range of 5.0 – 35.0 μg/mL. For accurate spectrophotometric determination of DEX in the ratio of the dosage form, multiple standard addition method was applied. HPLC technique was also applied for separation and quantification of both drugs. Chromatographic separation was attained by using Hypersil ODS-C18 (150 x 4.6 mm, 5 μm) column. The mobile phase was composed of 50 % methanol: 50 % phosphate buffer (pH 2.5). The column compartment was maintained at 25 °C. Flow rate was adjusted at 1.2 mL/min and detection was performed by DAD at 254 nm. The linearity of HPLC method was 5.0–100.0 μg/mL, and 5.0–50.0 μg/mL for KET and DEX, respectively. Simultaneous determination of both drugs was applied to lab-prepared eye drops that contain also benzalkonium chloride as inactive ingredient. The developed methods determined the cited drugs with good and acceptable % recovery. The results of the developed methods and a reported HPLC method were compared using one-way ANOVA test, F-test and student’s t-test at confidence level 95 %, and they show no significant statistical difference. Assessment of greenness of the developed methods in comparison with reported HPLC method was performed using different tools, including analytical eco-scale, GAPI and AGREE. HPLC-EAT was also performed to ensure greenness of developed HPLC method. Moreover, assessment of practicality, applicability, and functionality of developed and reported methods was evaluated by BAGI metric tool and WAC calculator, respectively. The developed methods allow simple, rapid, and accurate analysis of quality control samples that contain KET and DEX.

Harnessing the potency of eco-friendly calcium oxide derived from eggshells for enhanced photocatalytic activity and biocompatibility evaluation in HepG2 cell line

Efforts towards sustainable development and pollution prevention are driving the exploration of bio-Calcium oxide (CaO) production from eggshell waste. This work investigates the thermal conversion of eggshell derived CaCO3 into CaO. Powder X-ray diffraction and Fourier transform infrared spectroscopy confirm CaO composition, displaying a cubic structure with 2.405 Å bond length and a mid-bond electron density of 0.2298 e/ų. Electron density studies corroborate this, revealing a three-dimensional distribution and one-dimensional profile. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) confirms spherical CaO particles and EDAX spectra displays the presence of calcium and oxygen. UV absorption spectra reveal a 3.3 eV energy bandgap, showcasing CaO's photocatalytic potential. It demonstrates exceptional photocatalytic against congo red and methylene blue dyes, degrading them by 96.4 % and 98 %, respectively, via pseudo first-order kinetics. Additionally, CaO demonstrates promising anticancer activity against HepG2 liver cancer cells, with an IC50 value of 31.2 μg/mL, positioning it as a cost-effective and potent agent for both wastewater treatment and cancer therapy.

Photocatalytic properties of ZnO semiconductor nanoparticles green synthesized employing Ipomoea stans leave extracts

One of the biggest problems in the ecosystem is wastewater contaminated with industrial dyes. These pollutants have a very stable chemical structure, which causes complicated removal. However, a possible alternative for wastewater treatment is zinc oxide semiconductor nanoparticles (ZnO NPs). The approach of this study was the implementation of a green synthesis methodology for the obtention of ZnO nanoparticles employing Ipomoea stans (TV) leaves as extracts. The properties of the ZnO nanoparticles synthesized at 1 %, 2 %, and 4 % w/v (weight/volume) concentration of the extract were obtained from the characterization using different techniques. The FTIR analysis determined the presence of the active functional groups attached to the surface, which capped and stabilized the ZnO NPs; a band located in the range of 500-390 cm−1 confirms the presence of the Zn–O bond. The UV absorption spectra of all ZnO NPs samples were determined by executing the ultraviolet–visible spectroscopy technique, with a characteristic signal located at ∼370 nm and energy gap values between 3.036 eV and 3.101 eV. In addition, XRD patterns determined the average crystallite sizes to be 30.78 nm for ZnO-TV 1 %, 18.68 nm ZnO-TV 2 %, and 11.96 nm ZnO-TV 4 %, respectively. Furthermore, the results from transmission electron microscopy (TEM) displayed the following values of mean particle size of 21 nm, 24.4 nm, and 10.16 nm for ZnO-TV 1 %, ZnO-TV 2 % and ZnO-TV 4 % with S.D. 9.10, 12.5 and 3.6. Finally, the photocatalytic activity was evaluated utilizing the industrial dyes Methyl Orange, Methylene Blue, Rhodamine B, Malachite Green, and Congo Red. Obtaining outstanding results in the degradation of all industrial dyes. All syntheses achieved degradation greater than 91 % for methyl orange, methylene blue, and rhodamine B.

Exploring the uncharted seas: Metabolite profiling unleashes the anticancer properties of Oscillatoria salina

Marine cyanobacteria offer a rich source of varied natural products with both chemical and biological diversity. Oscillatoria salina (O. salina) is a filamentous non-heterocystous marine cyanobacterium from Oscillatoriaceae family. In this investigation, we have unveiled bioactive extracts from O. salina using two distinct solvent systems, revealing significant anticancer properties. Our assessment of the organic and aqueous extracts (MCE and AE) of O. salina demonstrated pronounced antiproliferative and antimetastatic effects. Notably, this study is the first to elucidate the anticancer and anti-metastatic potential of O. salina extracts in both 2D and 3D cell culture models. Both MCE and AE induced apoptosis, hindered cell proliferation, invasion, and migration in A549 non-small cell lung cancer cells, accompanied by alterations in cell morphology and cytoskeleton collapse. Moreover, MCE and AE induced spheroid disintegration in A549 cells. Transcriptomics analysis highlighted the significant involvement of Rap1 and p53 signaling pathways in mediating the observed antitumor effects. Mass spectroscopy characterization of these extracts identified 11 compounds, some known for their anticancer potential. HPLC analysis of AE revealed six peaks with UV absorption spectra resembling phycocyanin, a cyanobacterial pigment with well-known anticancer activity. Collectively, these findings underscore the anticancer potential of MCE and AE, containing bioactive metabolites with anticancer and antimetastatic properties.

Substituent effects in 2-hydroxybenzophenone-based ultraviolet absorbers

2-Hydroxybenzophenone is the simplest molecule among benzophenone-based UV absorbers. Changing the position and type of substituents affects the strength of intramolecular hydrogen bonding and thus modulates the UV absorption properties. In this work, 132 2-hydroxybenzophenone-based UV absorbers with different substituent positions and species were designed to investigate the substituent effect in their UV absorption properties. The results show that when the substituent positions are the same, the characteristic peaks of the compounds containing substituents of the same group of atoms or homologous groups correspond to similar wavelengths. When the substituent groups are the same, the wavelength redshift of the characteristic peaks of the UV absorption spectra of the compounds of the NX and NZ classes is more pronounced than that of the remaining species, and the substituent group containing N atoms causes the molecule to have a more pronounced wavelength redshift. The redshift of the characteristic absorption peaks corresponding to the wavelengths decreases with the increase of the energy level difference. Atoms-in-molecules (AIM) analysis showed that the electron-absorbing group in the compound enhances the hydrogen bond strength to a lesser extent than the electron-donating group. Natural Bond Orbital (NBO) analysis further revealed that the type and position of the substituent groups in the molecular structure influenced the strength of the intramolecular hydrogen bonding by affecting the distribution of the charges among individual atoms in the 2-hydroxybenzophenone molecules. This work aims to reveal the effect of substituents on the UV absorption properties of 2-hydroxybenzophenone-based molecules and to provide theoretical guidance for the design of such UV absorber molecules absorbing UV light at specific wavelengths.

Core Hole Effect to Valence Excitations: Tracking and Visualizing the Same Excitation in XPS Shake-Up Satellites and UV Absorption Spectra.

Introducing a core hole significantly alters the electronic structure of a molecule, and various X-ray spectroscopy techniques are available for probing the valence electronic structure in the presence of a core hole. In this study, we visually demonstrate the influence of a core hole on valence excitations by computing the ultraviolet absorption spectra and the shake-up satellites in X-ray photoelectron spectra for pyrrole, furan, and thiophene, as complemented by the natural transition orbital (NTO) analysis over transitions with and without a core hole. Employing equivalent core hole time-dependent density functional theory (ECH-TDDFT) and TDDFT methods, we achieved balanced accuracy in both spectra for reliable comparative analysis. We tracked the same involved valence transition in both spectra, offering a vivid illustration of the core hole effect via the change in corresponding particle NTOs introduced by a 1s core hole on a Cα, Cβ, or O atom. Our analysis deepens the understanding of the core hole effect on valence transitions, a phenomenon ubiquitously observed in general X-ray spectroscopic analyses.

Photocatalytic activities of Fe2O3 coated ZnO nanowires grown by electrochemical anodization method

In this study, the visible light photocatalytic activities of the ZnO and ZnO/Fe2O3 structures were investigated. Anodization of Zn plates to obtain ZnO nanowires was carried out by applying 35 V between 1 and 30 min durations. Fe2O3 layers were coated on initially obtained ZnO nanowires through a sol-gel spin-coating process. All samples were examined for morphological, structural, optical, and photocatalytic activities in detail. The results showed that the conducted anodization process was successful where up to micrometer-length nanowires were obtained. SEM images confirmed the presence of Fe2O3 deposits surrounding the nanowires, while UV and visible absorption spectra indicated increased absorption due to Fe2O3, leading to enhanced photocatalytic performance. The best-performing ZnO nanowire anodized for 5 min almost doubled its photocatalytic activity after Fe2O3 coating, in which an apparent reaction rate of 12.24 × 10−3 min−1 and degrading 90.32 % of the initial MB concentration was recorded.

Synthesis of Cu2+ doped ZnO@ZnCdS thin film: Optical and electrochemical characterization

Doping strategies modify the optical and electrochemical characteristics of materials. In this research, we investigated the impact of Cu2⁺ doping in ZnO@ZnCdS nanocomposites synthesized via the co-precipitation approach. A comprehensive analysis was conducted on the structural, morphological, optical, and electrochemical features of the samples using various techniques, including scanning electron microscopy (SEM), atomic force microscopy (AFM), Energy Dispersive X-ray analysis (EDX), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), UV–Visible absorption, and photoluminescence (PL). Notably, Cu2⁺ doping induces changes in morphology, crystal size, absorption spectra, and band gap energy. Surface investigations reveal a flower-like structure, while XRD analysis indicates an increase in crystal size from 25.5 to 35.2 in thin films with copper content. The absorption spectra of UV–visible-doped ZnO@ZnCdS thin films exhibit reduced peak intensity upon Cu2⁺ addition. Also, optical absorption analysis shows a shift towards longer wavelengths in the emission of ZnO@ZnCdS due to Cu2⁺ inclusion during doping. Likewise, the band gap energy ranges from 1.37 eV to 2.22 eV for ZnO@ZnCdS and Cu2⁺ doped ZnO@ZnCdS, respectively, as determined using Tauc plots. PL spectrum of the Cu2⁺ doped ZnO@CdS nanocomposite indicates emissions in the blue and green regions. Specifically, under 325 nm excitation, the copper-doped material displays a prominent blue and a less intense red emission at 420 nm at 685 nm, respectively. Furthermore, the electrochemical analysis revealed that doping caused a reduction in Rct and an elevation in CSP. These results offer important considerations for the development of cutting-edge functional optoelectronic materials.

Aggregation of N-Heteropolycyclic Aromatic Molecules: The Acridine Dimer and Trimer.

Polycyclic aromatic hydrocarbons and their nitrogen-substituted analogues are of great interest for various applications in organic electronics. The performance of such devices is determined not only by the properties of the single molecules, but also by the structure of their aggregates, which often form via self-aggregation. Gaining insight into such aggregation processes is a challenging task, but crucial for a fine-tuning of the materials properties. In this work, an efficient approach for the generation and characterisation of aggregates is described, based on matrix-isolation experiments and quantum-chemical calculations. This approach is exemplified for aggregation of acridine. The acridine dimer and trimer are thoroughly analysed on the basis of experimental and calculated UV and IR absorption spectra, which agree well with each other. Thereby a novel structure of the acridine dimer is found, which disagrees with a previously reported one. The calculations also show the changes from excitonic coupling towards orbital interactions between two molecules with decreasing distance to each other. In addition, a structure of the trimer is determined. Finally, an outlook is given on how even higher aggregates can be made accessible through experiment.

Sequence-Dependent Surface Coverage of ssDNA Coatings on Single-Wall Carbon Nanotubes.

A combination of experimental measurements and molecular dynamics (MD) simulations was used to investigate how the surfaces of single-wall carbon nanotubes (SWCNTs) are covered by adsorbed ssDNA oligos with different base compositions and lengths. By analyzing the UV absorption spectra of ssDNA-coated SWCNTs before and after coating displacement by a transparent surfactant, the mass ratios of adsorbed ssDNA to SWCNTs were determined for poly-T, poly-C, GT-containing, and AT-containing ssDNA oligos. Based on the measured mass ratios, it is estimated that an average of 20, 22, 26, or 32 carbon atoms are covered by one adsorbed thymine, cytosine, adenine, or guanine nucleotide, respectively. In addition, the UV spectra revealed electronic interactions of varying strengths between the nucleobase aromatic rings and the nanotube π-systems. Short poly-T DNA oligos show stronger π-π stacking interactions with SWCNT surfaces than do short poly-C DNA oligos, whereas both long poly-C and poly-T DNA oligos show strong interactions. These experiments were complemented by MD computations on simulated systems that were constrained to match the measured ssDNA/SWCNT mass ratios. The surface coverages computed from the MD results varied with oligo composition in a pattern that correlates higher measured yields of nanotube fluorescence with greater surface coverage.

Associating LOFAR Galactic Faraday structures with the warm neutral medium

Faraday tomography observations with the Low Frequency Array (LOFAR) have unveiled a remarkable network of structures in polarized synchrotron emission at high Galactic latitudes. The observed correlation between LOFAR structures, dust polarization, and HI emission suggests a connection to the neutral interstellar medium (ISM). We investigated this relationship by estimating the rotation measure (RM) of the warm neutral (partially ionized) medium (WNM) in the local ISM. Our work combines UV spectroscopy from FUSE and dust polarization observations from Planck with LOFAR data. We derived electron column densities from UV absorption spectra toward nine background stars, within the field of published data from the LOFAR two-meter sky survey. The associated RMs were estimated using a local magnetic field model fitted to the dust polarization data of Planck. A comparison with Faraday spectra at the position of the stars suggests that LOFAR structures delineate a slab of magnetized WNM and synchrotron emission, located ahead of the bulk of the warm ionized medium. This conclusion establishes an astrophysical framework for exploring the link between Faraday structures and the dynamics of the magnetized multiphase ISM. It will be possible to test it on a larger sample of stars when maps from the full northern sky survey of LOFAR become available.

The Gas Phase Protonation Sites of Six Naturally Occurring Nicotinoids.

The gas phase protonation sites of six naturally occurring nicotinoids, namely nicotine (NIC), nornicotine (NOR), anabasine (ANB), anatabine (ANT), cotinine (COT), and myosmine (MYO), consisting of a common Pyridine and differing non-Pyridine rings, have been determined for the first time at the physiological temperature from cryogenic ion trap infrared spectroscopy and electronic structure calculations. The protonation site on either of these two rings is related to the nicotinoid's biological activity. At room temperature, NIC is a mixture of Pyridine and Pyrrolidine (non-Pyridine) protomers, whereas NOR, ANB, ANT, and COT are pure Pyridine protomers and finally MYO is mostly a Pyroline (non-Pyridine) protomer. The nearly planar structure of MYO-H+, induced by the presence of a conjugated π system and confirmed from calculations and the UV absorption spectra, breaks from the trends observed for NIC, NOR, and ANB, since its structure is drastically different from the structures of the other nicotinoids.

A ratiometric fluorescent probe for cysteine and glutathione differentiation and its application for cysteine detection in foods

Cysteine (Cys) and glutathione (GSH) are crucial biothiols implicated in cellular redox balance, necessitating accurate detection methods. Herein, we developed a novel fluorescent probe based on the fluorescent dye pyronin (PYR), capable of monitoring both Cys-and GSH using ratiometric fluorescence signals. The probe, named PYR-CG, where "C" stands for Cys-and "G" stands for GSH, demonstrates selective detection capabilities for Cys-and GSH. UV absorption and fluorescence emission spectra changes revealed distinct shifts upon interaction with Cys-and GSH. Theoretical and experimental studies validated PYR-CG's responsiveness to Cys-and GSH, elucidating its mechanism as a ratiometric probe. Notably, PYR-CG exhibited rapid response kinetics for Cys-and GSH, with low detection limits of 88 nM and 164 nM, respectively. Importantly, PYR-CG demonstrated exceptional selectivity for Cys-and GSH over interfering analytes. Screening of molecules with similar structures to Cys-further affirmed PYR-CG's specificity, particularly towards N-terminal Cys-in peptides. Furthermore, recovery experiments underscored PYR-CG's reliability for quantitative Cys-detection in complex food samples. Our findings highlight the innovative design and practical applicability of PYR-CG, offering a valuable tool for sensitive and selective detection of Cys-in diverse biological and food samples.

The study of interaction between human serum albumin and alternaria toxins using multi-spectroscopy, molecular docking and molecular dynamic

Alternaria Toxins (ATs) is a kind of mycotoxin widely existed in fruits, vegetables and processed foods. Four ATs including alternariol monomethyl ether (AME), 3′-hydroxyalternariol monomethyl ether (3HME), altenuisol (ALI) and altenuene (ALT) isolated from Alternaria interacting with human serum albumin (HSA) were studied. The fluorescence quenching method proved that the four ATs and HSA were all statically quenched and formed stable complexes. The binding constant of each AT was calculated after experiment, which were AME: 1.26 × 1013 M−1s−1; 3HME: 2.00 × 1013 M−1s−1; ALI: 4.43 × 1012 M−1s−1 and ALT: 3.64 × 1012 M−1s−1 in 298 K, respectively. The interaction force of each AT and HSA was determined by thermodynamic calculation, which shown that the four systems all had van der Waals forces and hydrogen bonds involved in their interaction, but in AME and ALI, electrostatic action was also involved and in 3HME and ALT, hydrophobic action was also involved. It was proved that combination processes were spontaneous heat release process. 3HME and ALT were confirmed to be located at binding site I, wheras the other two were at site II. Synchronous fluorescence, three-dimensional (3D) fluorescence, UV absorption and CD spectra were used to investigate the effect of ATs interaction with HSA on the structure and function of HSA. Molecular docking provided a visual understanding and validation of the conclusions, while explaining the preliminary conclusions of the experiment. The root mean square deviation (RMSD), root mean square fluctuation (RMSF), radius of gyration (Rg) were calculated by molecular dynamics simulation.