Optoelectronic Response to the Fluor Ion Bond on 4-(4,4,5,5-Tetramethyl-1,3,2-dioxoborolan-2-yl)benzaldehyde

Boronate esters are a class of compounds containing a boron atom bonded to two oxygen atoms in an ester group, often being used as precursors in the synthesis of other materials. The characterization of the structure and properties of esters is usually carried out by UV-visible, infrared, and nuclear magnetic resonance (NMR) spectroscopic techniques. With the aim to better understand our experimental data, in this article, the density functional theory (DFT) is used to analyze the UV-visible and infrared spectra, as well as the isotropic shielding and chemical shifts of the hydrogen atoms 1H, carbon 13C and boron 11B in the compound 4-(4,4,5,5-tetramethyl-1,3,2-dioxoborolan-2-yl)benzaldehyde. Furthermore, this study considers the change in its electronic and spectroscopic properties of this particular ester, when its boron atom is coordinated with a fluoride anion. The calculations were carried out using the LSDA and B3LYP functionals in Gaussian-16, and PBE in CASTEP. The results show that the B3LYP functional gives the best approximation to the experimental data. The formation of a coordinated covalent B-F bond highlights the remarkable sensitivity of the NMR chemical shifts of carbon, oxygen, and boron atoms and their surroundings. Furthermore, this bond also highlights the changes in the electron transitions bands n → π* and π → π* during the absorption and emission of a photon in the UV-vis, and in the stretching bands of the C=C bonds, and bending of BO2 in the infrared spectrum. This study not only contributes to the understanding of the properties of boronate esters but also provides important information on the interactions and responses optoelectronic of the compound when is bonded to a fluorine atom.

Multispectroscopic and computational techniques to study the interaction of anthraquinone appended sensor with calf thymus DNA

An anthraquinone based derivative (AQ) has been designed and synthesized to find its applications for the interactions with calf thymus DNA (ctDNA) involving various spectroscopic techniques, thermodynamic and computational approaches. The UV-vis studies pointed to interaction of AQ with ctDNA via groove binding mode, which has been further supported well by the ionic strength studies, viscosity measurement, circular dichroism and melting temperature (Tm) curves. These findings have been further validated by dye-displacement assay and molecular docking studies. The analysis of thermodynamic parameters supports that the AQ-ctDNA binding is entropy favoured and enthalpy disfavoured and main acting binding interaction is hydrophobic interaction. The outcomes of the molecular modelling suggested that AQ might have entered the A-T abundant area of the ctDNA.Communicated by Ramaswamy H. Sarma.

The Iodine/Iodide/Starch Supramolecular Complex

The nature of the blue color in the iodine-starch reaction (or, in most cases, iodine-iodide-starch reaction, i.e., I2 as well as I- are typically present) has for decades elicited debate. The intensity of the color suggests a clear charge-transfer nature of the band at ~600 nm, and there is consensus regarding the fact that the hydrophobic interior of the amylose helix is the location where iodine binds. Three types of possible sources of charge transfer have been proposed: (1) chains of neutral I2 molecules, (2) chains of poly-iodine anions (complicated by the complex speciation of the I2-I- mixture), or (3) mixtures of I2 molecules and iodide or polyiodide anions. An extended literature review of the topic is provided here. According to the most recent data, the best candidate for the "blue complex" is an I2-I5--I2 unit, which is expected to occur in a repetitive manner inside the amylose helix.

The Antifungal Activities of Silver Nano-Aggregates Biosynthesized from the Aqueous Extract and the Alkaline Aqueous Fraction of Rhazya stricta against Some Fusarium Species

Rhazya stricta is a major medicinal species used in indigenous medicinal herbal medications in South Asia, the Middle East, Iran, and Iraq to treat a variety of ailments. The current study aimed to investigate the antifungal properties of biosynthesized silver nanoparticles (AgNPs) made from R. stricta aqueous extract and its alkaline aqueous fraction. Fourier transform infrared spectroscopy (FTIR), UV-vis spectrophotometry, dynamic light scattering (DLS), and transmitted electron microscopy (TEM) were used to characterize AgNPs. The produced extracts and AgNPs were tested for their antifungal efficacy against four Fusarium spp. All of the characterization experiments proved the biosynthesis of targeted AgNPs. FTIR showed a wide distribution of hydroxyl, amino, carboxyl, and alkyl functional groups among all preparations. The DLS results showed that the produced Aq-AgNPs and the Alk-AgNPs had an average size of 95.9 nm and 54.04 nm, respectively. On the other hand, TEM results showed that the Aq-AgNPs and Alk-AgNPs had average diameters ranging from 21 to 90 nm and 7.25 to 25.32 nm. Both AgNPs absorbed UV light on average at 405 nm and 415 nm, respectively. Regarding the fungicidal activity, the highest doses of Aq-extract and Aq-AgNPs inhibited the mycelial growth of F. incarnatum (19.8%, 87.5%), F. solani (28.1%, 72.3%), F. proliferatum (37.5%, 75%), and F. verticillioides (27.1%, 62.5%), respectively (p < 0.001). Interestingly, the Alk-fraction had stronger inhibition than the biosynthesized AgNPs, which resulted in complete inhibition at the doses of 10% and 20% (p < 0.001). Furthermore, microscopic analysis demonstrated that both AgNPs caused obvious morphological alterations in the treated organisms when compared to the control. In conclusion, R. stricta's Aq-extract, alkaline fraction, and their biosynthesized AgNPs show substantial antifungal efficacy against several Fusarium spp. It is the first study to highlight the prospective biological activities of R. stricta Aq-extract and its alkaline fraction against F. incarnatum, F. proliferatum, and F. verticillioides. In addition, it is the first opportunity to deeply investigate the ultrastructural changes induced in the Fusarium species treated with R. stricta crude Aq-extract and its biosynthesized AgNPs. More studies are required to investigate their biological effect against other Fusarium or fungal species.

Mixed-Valence Tetrametallic Iridium Chains

Neutral [X-{Ir2 }-{Ir2 }-X] (X=Cl, Br, SCN, I) and dicationic [L-{Ir2 }-{Ir2 }-L]2+ (L=MeCN, Me2 CO) tetrametallic iridium chains made by connecting two dinuclear {Ir2 } units ({Ir2 }=[Ir2 (μ-OPy)2 (CO)4 ], OPy=2-pyridonate) by an iridium-iridium bond are described. The complexes exhibit fractional averaged oxidation states of +1.5 and electronic delocalization along the metallic chain. While the axial ligands do not significantly affect the metal-metal bond lengths, the metallic chain has a significant impact on the iridium-L/X bond distances. The complexes show free rotation around the unsupported iridium-iridium bond in solution, with a low-energy transition state for the chloride chain. The absorption spectra of these complexes show characteristic bands at 438-504 nm, which can be fine-tuned by varying the terminal capping ligands.

Catalytic Degradation of Triphenylmethane Dyes with an Iron Porphyrin Complex as a Cytochrome P450 Model

The organic dyes used in printing and dyeing wastewater have complex components, diverse structures and strong chemical stability, which make them not suitable for treatment and difficult to degrade in the environment. Porphyrins are macromolecules with 18 π electrons formed by four pyrrole molecules connected with a methylene bridge that has a stable structure. Porphyrin combines with iron to form an active intermediate with a structure similar to the cytochrome P450 enzyme, so they are widely used in the biomimetic field. In the current study, 5,10,15,20-tetra (4-carboxyphenyl) porphine ferric chloride (III) (Fe(III)TCPP) was used as a catalyst and iodosobenzene was used as an oxidant to explore the catalytic degradation of triphenylmethane dyes, such as rhodamine B (RhB) and malachite green (MG). The results of UV-Vis spectral analysis have shown that the conversion rate of the rhodamine B was over 90% when the amount of Fe(III)TCPP was 0.027 mM and the amount of iodosobenzene was eight equivalents. When the catalyst was 0.00681 mM and the amount of the oxidant was five equivalents, the conversion rate of the malachite green reached over 95%. This work provides a feasible method for the degradation of triphenylmethane dyes.

Antibacterial Activity of the Green Synthesized Plasmonic Silver Nanoparticles with Crystalline Structure against Gram-Positive and Gram-Negative Bacteria

Nanoparticles (NPs) have attracted considerable interest in numerous fields, including agriculture, medicine, the environment, and engineering. The use of green synthesis techniques that employ natural reducing agents to reduce metal ions and form NPs is of particular interest. This study investigates the use of green tea (GT) extract as a reducing agent for the synthesis of silver NPs (Ag NPs) with crystalline structure. Several analytical techniques, including UV-visible spectrophotometry, Fourier transform infrared (FTIR) spectroscopy, high-resolution transmission electron microscopy (HR-TEM), and X-ray diffraction (XRD), were used to characterize the synthesized Ag NPs. The results of UV-vis revealed that the biosynthesized Ag NPs exhibited an absorbance plasmonic resonance peak at 470 nm. According to FTIR analyses, the attachment of Ag NPs to polyphenolic compounds resulted in a decrease in intensity and band shifting. In addition, the XRD analysis confirmed the presence of sharp crystalline peaks associated with face-centered cubic Ag NPs. Moreover, HR-TEM revealed that the synthesized particles were spherical and 50 nm in size on average. The Ag NPs demonstrated promising antimicrobial activity against Gram-positive (GP) bacteria, Brevibacterium luteolum and Staphylococcus aureus, and Gram-negative (GN) bacteria, Pseudomonas aeruginosa and Escherichia coli, with a minimal inhibitory concentration (MIC) of 6.4 mg/mL for GN and 12.8 mg/mL for GP. Overall, these findings suggest that Ag NPs can be utilized as effective antimicrobial agents.

Theoretical model study of adsorbed antimalarial-graphene dimers: doping effects, photophysical parameters, intermolecular interactions, edge adsorption, and SERS

Future diagnostics and therapy applications are in part riding on the discovery and implementation of new optical techniques and strategies (which often derive from dyads) for example, prediction of features in surface-enhanced Raman spectroscopy requires the study of chromophore-chromophore interactions involve intermolecular forces, drug delivery, and photo mechanisms which are of great interest. New matches between chromophore systems (i.e. FRET), and π-delocalized surfaces are important to study. We explore low-molecular weight drug molecules and their interaction with the reporter material/surface of graphene. Bonding, charge transfer and orbital interactions for 2-amino-5-(1-methyl-5-nitro-2-imidazolyl)-1,3,4-thiadiazole (megazol or AMIT) on graphene were carried out. The graphene model substrate was monotonically/monatomically substituted (doped) with one neutral heteroatom (N/O/S/B) in place of one carbon center; chemical adsorption of AMIT is due to charge transfer from doped graphene to AMIT (DFT). Our AMIT-nanocluster studies show that the nanoclusters will act as a sensor component for the detection of drugs due to SERS. Our findings identified that the greater the energy of the charge transfer, the stronger the calculated chemical adsorption. Additionally, charge transfer is highest for the N-doped systems and least for pristine graphene, resulting in a stronger adsorption energy for N-doped graphene. Mulliken charge analysis of structures confirms enhancement found in QD-AMIT systems.Communicated by Ramaswamy H. Sarma.

On the Origin of the Blue Color in The Iodine/Iodide/Starch Supramolecular Complex

The nature of the blue color in the iodine-starch reaction is still a matter of debate. Some textbooks still invoke charge-transfer bands within a chain of neutral I₂ molecules inside the hydrophobic channel defined by the interior of the amylose helical structure. However, the consensus is that the interior of the helix is not altogether hydrophobic-and that a mixture of I₂ molecules and iodide anions reside there and are responsible for the intense charge-transfer bands that yield the blue color of the "iodine-starch complex". Indeed, iodide is a prerequisite of the reaction. However, some debate still exists regarding the nature of the iodine-iodine units inside the amylose helix. Species such as I₃^-, I₅^-, I₇^- etc. have been invoked. Here, we report UV-vis titration data and computational simulations using density functional theory (DFT) for the iodine/iodide chains as well as semiempirical (AM1, PM3) calculations of the amylose-iodine/iodide complexes, that (1) confirm that iodide is a pre-requisite for blue color formation in the iodine-starch system, (2) propose the nature of the complex to involve alternating sets of I₂ and I_x^- units, and (3) identify the nature of the charge-transfer bands as involving transfer from the I_x^- σ* orbitals (HOMO) to I₂ σ* LUMO orbitals. The best candidate for the "blue complex", based on DFT geometry optimizations and TD-DFT spectral simulations, is an I₂-I₅-I₂ unit, which is expected to occur in a repetitive manner inside the amylose helix.

Ring Vibrations to Sense Anionic Ibuprofen in Aqueous Solution as Revealed by Resonance Raman

We unravel the potentialities of resonance Raman spectroscopy to detect ibuprofen in diluted aqueous solutions. In particular, we exploit a fully polarizable quantum mechanics/molecular mechanics (QM/MM) methodology based on fluctuating charges coupled to molecular dynamics (MD) in order to take into account the dynamical aspects of the solvation phenomenon. Our findings, which are discussed in light of a natural bond orbital (NBO) analysis, reveal that a selective enhancement of the Raman signal due to the normal mode associated with the C-C stretching in the ring, νC=C, can be achieved by properly tuning the incident wavelength, thus facilitating the recognition of ibuprofen in water samples.

Data on physicochemical properties of natural clay and natural clay/multiwalled carbon nanotubes composite materials for various applications possibilities

Natural materials can provide cost-effective way in the development of various products for specific applications. On the hand, physicochemical properties of composite materials can be enhanced to perform a specific process of interest such as wastewater treatment. Clay materials have been used for many applications including brick making and wastewater treatment. To enhance the properties of natural materials such as clay, multiwalled carbon nanotubes (MWCNTs) were used to enhance the properties of natural clays. Natural clays and MWCNTs composites were characterized to provide insights as a starting point for various applications. There are two sets of data presented in this study: i) raw material, unheated and heated (at 900 °C); ii) natural clay, MWCNTs and natural clay/MWCNTs composites. The chemical composition and phase identification analyzes were carried out using X-ray Fluorescence (XRF) and X-Ray Diffraction (XRD), respectively. A Fourier-transform infrared (FTIR) spectrometer was used to determine the functional groups of the samples. The UV-vis analyzes were carried out to investigate the reflectance percentage of the natural clays and the composites samples. The Thermogravimetric analysis (TGA) analyzes were performed to investigate the weight loss and dehydration process of the samples. The presented data showed that natural clays and natural clays/MWCNTs composites can be used for various applications such as construction industry, for cosmetic usages and for the removal of pollutants in aqueous solutions.

Comparison of Solution Chemical Properties and Biological Activity of Ruthenium Complexes of Selected β-Diketone, 8-Hydroxyquinoline and Pyrithione Ligands

In this work, the various biological activities of eight organoruthenium(II) complexes were evaluated to reveal correlations with their stability and reactivity in aqueous media. Complexes with general formula [Ru(η6-p-cymene)(X,Y)(Z)] were prepared, where (X,Y) represents either an O,O-ligand (β-diketone), N,O-ligand (8-hydroxyquinoline) or O,S-pyrithione-type ligands (pyrithione = 1-hydroxypyridine-2(1H)-thione) with Cl- or 1,3,5-triaza-7-phosphaadamantane (PTA) as a co-ligand (Z). The tested complexes inhibit the chlamydial growth on HeLa cells, and one of the complexes inhibits the growth of the human herpes simplex virus-2. The chlorido complexes with N,O- and O,S-ligands displayed strong antibacterial activity on Gram-positive strains including the resistant S. aureus (MRSA) and were cytotoxic in adenocarcinoma cell lines. Effect of the structural variation on the biological properties and solution stability was clearly revealed. The decreased bioactivity of the β-diketone complexes can be related to their lower stability in solution. In contrast, the O,S-pyrithione-type complexes are highly stable in solution and the complexation prevents the oxidation of the O,S-ligands. Comparing the binding of PTA and the chlorido co-ligands, it can be concluded that PTA is generally more strongly coordinated to ruthenium, which at the same time decreased the reactivity of complexes with human serum albumin or 1-methylimidazole as well as diminished their bioactivity.

Determination of free sulfhydryl contents for proteins including monoclonal antibodies by use of SoloVPE

Free sulfhydryls are important properties of protein products including monoclonal antibodies (mAbs). Here, a new technology, variable pathlength extension (SoloVPE), is employed to quantify the amount of free sulfhydryl in monoclonal antibodies (mAbs) using the well-known Ellman reagent. Briefly, the unbound thiols (free sulfhydryls) of proteins including mAbs react with Ellman reagent to produce a 2-nitro-5-thiobenzoate (TNB^2-) which is detected at visible wavelength of 412 nm and quantified. The method does not require dilution of antibody samples, is simple, reproducible and takes less than one hour to complete. Values obtained by the new method are compared to literature values from traditional UV or fluorescence methods with agreements. Qualification and trending data over two years of method utilization in our labs support that assay variability is minimal with an intermediate precision of relative standard deviation (RSD) ≤ 10 % and a limit of quantification (LOQ) of 0.1 mol/mol, which is sufficient to measure free sulfhydryl content in proteins including mAbs.

Drying-Time Study in Graphene Oxide

Graphene oxide (GO) exhibits different properties from those found in free-standing graphene, which mainly depend on the type of defects induced by the preparation method and post-processing. Although defects in graphene oxide are widely studied, we report the effect of drying time in GO and how this modifies the presence or absence of edge-, basal-, and sp³-type defects. The effect of drying time is evaluated by Raman spectroscopy, UV-visible spectroscopy, and transmission electron microscopy (TEM). The traditional D, G, and 2D peaks are observed together with other less intense peaks called the D', D*, D**, D+G, and G+D. Remarkably, the D* peak is activated/deactivated as a direct consequence of drying time. Furthermore, the broad region of the 2D peak is discussed as a function of its deconvoluted 2D_1A, 2D_2A, and D+G bands. The main peak in UV-visible absorption spectra undergoes a redshift as drying time increases. Finally, TEM measurements demonstrate the stacking of exfoliated GO sheets as the intercalated (water) molecules are removed.

Fabrication of Alternating Copolymers Based on Cyclopentadithiophene-Benzothiadiazole Dicarboxylic Imide with Reduced Optical Band Gap: Synthesis, Optical, Electrochemical, Thermal, and Structural Properties

A series of alternating copolymers containing cyclopentadithiophene (CPDT) flanked by thienyl moieties as electron-donor units and benzothiadiazole dicarboxylic imide (BTDI) as electron-acceptor units were designed and synthesized for solar cell applications. Different solubilizing side chains, including 2-ethylhexyl chains and n-octyl chains were attached to CPDT units, whereas 3,7-dimethyloctyl chains and n-octyl chains were anchored to the BTDI moieties. The impact of these substituents on the solubilities, molecular weights, optical and electrochemical properties, and thermal and structural properties of the resulting polymers was investigated. PCPDTDTBTDI-EH, DMO was synthesized via Suzuki polymerization, whereas PCPDTDTBTDI-8, DMO, and PCPDTDTBTDI-EH, 8 were prepared through direct arylation polymerization. PCPDTDTBTDI-8, DMO has the highest number average molecular weight (Mn = 17,400 g mol-1) among all polymers prepared. The PCPDTDTBTDI-8, DMO and PCPDTDTBTDI-8, 8 which have n-octyl substituents on their CPDT units have comparable optical band gaps (Eg ~ 1.3 eV), which are around 0.1 eV lower than PCPDTDTBTDI-EH, DMO analogues that have 2-ethylhexyl substituents on their CPDT units. The polymers have their HOMO levels between -5.10 and -5.22 eV with PCPDTDTBTDI-EH, DMO having the deepest highest occupied molecular orbital (HOMO) energy level. The lowest unoccupied molecular orbital (LUMO) levels of the polymers are between -3.4 and -3.5 eV. All polymers exhibit good thermal stability with decomposition temperatures surpassing 350 °C. Powder X-ray diffraction (XRD) studies have shown that all polymers have the amorphous nature in solid state.

Improvement in Cobalt Phosphate Electrocatalyst Activity toward Oxygen Evolution from Water by Glycine Molecule Addition and Functional Details

Electrochemical water splitting using renewable energy shows promise for the development of sustainable hydrogen production methods. The process requires a highly active electrocatalyst for oxygen evolution to improve the overall water splitting efficiency. The present study showed that oxygen evolution improved dramatically upon the addition of glycine to cobalt phosphate, when the glycine was added to the electrolyte solution during electrodeposition. The functionality of the organic molecules was investigated using in situ UV-vis absorption, in situ X-ray absorption fine structure, and in situ infrared (IR) absorption spectroscopy in the attenuated total reflection mode. The results demonstrated that the glycine molecules assembled cobalt oxide clusters composed of CoO₆ (CoOOH) octahedrons a few nanometers in diameter upon the electrodeposition of cobalt catalysts. This suggests that the cobalt-glycine catalyst can decompose water to oxygen gas efficiently, because the number of cobalt oxide clusters increased as active reaction sites upon the addition of glycine molecules.

Methods for thermal denaturation studies of nucleic acids in complex with fluorogenic dyes

Thermal denaturation is a common technique in the biophysical study of nucleic acids. These experiments are typically performed by monitoring the increase in absorbance (hyperchromism) of a sample at 260nm with temperature (Mergny & Lacroix, 2003; Puglisi & Tinoco, 1989). This wavelength is chosen as nucleic acids of mixed sequence typically exhibit their maximum absorbance here. Exceptions exist, however, some noncanonical nucleic acid structures exhibit differing spectral changes with temperature, resulting in other wavelengths being convenient reporters of secondary structure. In the case of nucleic acids that bind visible light-absorbing ligands, such as fluorogenic aptamers, another wavelength can be a convenient reporter of secondary structure stability and RNA-ligand recognition. As it can be difficult, if not impossible, to know which wavelength to employ a priori, we have developed a system for obtaining the full UV-visible spectrum of a sample at each wavelength, allowing for the subsequent extraction of the absorbance-temperature profile at the desired wavelength. Here, we describe the apparatus and software used to do so. We also describe another technique for the use of a qPCR instrument for measuring secondary structure stability of fluorescent nucleic acid-ligand complexes.

Investigating Stability and Tautomerization of Gossypol-A Spectroscopy Study

The stability of gossypol was investigated by the spectroscopic method. Gossypol was dissolved in three different solvents (CHCl₃, DMSO, and CH₃OH) under different storage conditions (dark and with nitrogen protection, natural light and with nitrogen protection, ambient air conditions) for different time intervals (0 days, 3 days, 5 days, 7 days, 15 days, 30 days, and 45 days) at room temperature. Then, the stability of gossypol was investigated by ¹H NMR, UV-vis, and HPLC-QTOF-MS spectrometry. Results showed that gossypol existed in aldehyde–aldehyde form in chloroform within five days. Then, both aldehyde–aldehyde and lactol–lactol tautomeric forms existed and maintained a stable solution for 45 days. Gossypol dissolved in methanol mainly existed in aldehyde–aldehyde form. Only a tiny amount of lactol–lactol was found in freshly prepared methanol solution. Gossypol was found to only exist in lactol–lactol form between 30–45 days. Gossypol existed in aldehyde–aldehyde, lactol–lactol, and ketol–ketol forms in dimethyl sulfoxide, and there was a competitive relationship between aldehyde–aldehyde and lactol–lactol form during the 45 days. Among all the solvents and conditions studied, gossypol was found to be highly stable in chloroform. Under the tested conditions, the natural light and atmospheric oxygen had little effect on its stability. Although the spectroscopy data seemed to be changed over time in the three different solvents, it was actually due to the tautomeric transformation rather than molecular decomposition.

Separation and size characterization of zinc oxide nanoparticles in environmental waters using asymmetrical flow field-flow fractionation

There are few studies on separation and size characterization of zinc oxide nanoparticles (ZnO-NPs), which have wide applications in several science and technology areas, in the environment. In this work, we report a method for the separation and size characterization of ZnO-NPs by asymmetrical flow field-flow fractionation (AF4) coupled to UV-vis detector. Experimental conditions such as composition of the carrier solution, focus time, crossflow, detector flow rate and injection volume were systematically studied in terms of NPs separation, recovery, and repeatability. Size characterization was achieved using polystyrene nanoparticles as a size standard and a mixture of < 35 nm (NP-A) and < 100 nm (NP-B) ZnO-NPs were separated and size characterized posterior preconcentration using ultracentrifugation. The method was also employed to characterize the size of homemade ZnO-NPs, and the results were in concordance with dynamic light scattering (DLS) analysis and thus, the method can be used as an alternate method. Upon application on environmental water samples, the two ZnO-NPs, NP-A and NP-B, have been separated and size characterized. The estimated hydrodynamic sizes of the NP-A and NP-B were found to be in the range of 83-97 nm and 188-202 nm, respectively, with good precision (RSD, <11%), suggesting that the current method can satisfactorily separate and generate information about sizes of the NPs in samples with a complex matrix. Therefore, the developed technique can be used as a baseline to investigate size related environmental processes of the NPs in environmental water samples.

Resonance Raman Spectro-Electrochemistry to Illuminate Photo-Induced Molecular Reaction Pathways

Electron transfer reactions play a key role for artificial solar energy conversion, however, the underlying reaction mechanisms and the interplay with the molecular structure are still poorly understood due to the complexity of the reaction pathways and ultrafast timescales. In order to investigate such light-induced reaction pathways, a new spectroscopic tool has been applied, which combines UV-vis and resonance Raman spectroscopy at multiple excitation wavelengths with electrochemistry in a thin-layer electrochemical cell to study [Ru^II(tbtpy)₂]²⁺ (tbtpy = tri-tert-butyl-2,2':6',2''-terpyridine) as a model compound for the photo-activated electron donor in structurally related molecular and supramolecular assemblies. The new spectroscopic method substantiates previous suggestions regarding the reduction mechanism of this complex by localizing photo-electrons and identifying structural changes of metastable intermediates along the reaction cascade. This has been realized by monitoring selective enhancement of Raman-active vibrations associated with structural changes upon electronic absorption when tuning the excitation wavelength into new UV-vis absorption bands of intermediate structures. Additional interpretation of shifts in Raman band positions upon reduction with the help of quantum chemical calculations provides a consistent picture of the sequential reduction of the individual terpyridine ligands, i.e., the first reduction results in the monocation [(tbtpy)Ru(tbtpy^•)]⁺, while the second reduction generates [(tbtpy^•)Ru(tbtpy^•)]⁰ of triplet multiplicity. Therefore, the combination of this versatile spectro-electrochemical tool allows us to deepen the fundamental understanding of light-induced charge transfer processes in more relevant and complex systems.

A Simple and Effective Colorimetric Assay for Glucose Based on MnO₂ Nanosheets

Simple and effective methods for the detection of the level of blood glucose are closely linked to the monitoring of people's health. In the study, MnO₂ nanosheets with absorption range of 300 nm~500 nm and obvious yellow color were easily prepared and applied to detect glucose through their absorbance and color. The proposed method is based on the fact that a specific concentration of glucose can be quantitatively transformed into hydrogen peroxide (H₂O₂) under the catalytic effect of glucose oxidase. Based on the redox reaction of MnO₂ with H₂O₂, yellow MnO₂ can be converted into colorless Mn²⁺ to monitor the concentration of glucose. Under optimal conditions, a simple and effective visual assay for the sensitive and reliable detection of glucose was developed. The linear range was estimated to the range from 0 μM to 100 μM, with a detection limit of 12.8 μM. Furthermore, the proposed colorimetric assay based on MnO₂ nanosheets can effectively detect blood glucose of clinical serum samples with accuracy and convenience.

Impact of Synergistic Association of ZnO-Nanorods and Symbiotic Fungus Piriformospora indica DSM 11827 on Brassica oleracea var. botrytis (Broccoli)

In the present work, novel nanotool called 'nano-embedded fungus' formed by impact of synergistic association of ZnO-nanorods and fungus Piriformospora indica DSM 11827, for growth of Brassica oleracea var. botrytis (Broccoli) is reported. ZnO-nanorods were synthesized by mechanical assisted thermal decomposition process and characterized by scanning electron microscopy (SEM) for morphology, X-ray diffraction for structural studies and UV-vis absorption spectroscopy for band gap determination. Nanoembedded fungus is prepared by optimizing ZnO-nanorods concentration (500 ppm) which resulted in the increased biomass of P. indica, as confirmed by dry weight method, spore count, spread plate and microscopy techniques viz. SEM and confocal microscopy. Enhancement in B. oleracea var. botrytis is reported on treatment with nanoembedded fungus. According to the authors, this is the first holistic study focusing on the impact of ZnO-nanorods in the enhancement of fungal symbiont for enhanced biomass productivity of B. oleracea plant.

[Optical Characteristics of Dissolved Organic Matter from Two Different Full Mixed Reservoirs in Winter Based on UV-vis and EEMs]

The differences in the resource and characteristics of DOM between Zhoucun Reservoir and Jinpen Reservoir were studied by fluorescence ultraviolet-visible (UV-vis) and excitation-emission matrix spectra combined with parallel analysis (EEMs-PARAFAC). The results showed that three fluorescent components were identified by PARAFAC model in Zhoucun Reservoir and Jinpen Reservoir, including long wave humus-like component (C1: 350/460 nm), visible fulvic-like (C2: 335/410 nm) and protein-like (C3: 260,285/360 nm). However, the fluorescence intensity and the relative proportions of DOM exhibited significant difference (P<0.01) in two reservoirs. Moreover, the concentration of protein-like component in Zhoucun Reservoir was higher than that in Jinpen Reservoir, while the concentration of humus-like component presented the opposite trend. Based on the comparison of fluorescence index, biological index, humification index and the freshness index, the DOM of Zhoucun Reservoir where the land-use type was cultivated, livestock and residential, the internal pollution of sediments was serious, indicating a strong autochthonous component and aquatic bacterial origin, whereas the DOM of Jinpen Reservoir dominated by forest system had a higher terrigenous contribution in winter. From all the results, hydrological conditions of the reservoir and the characteristics of coastal ecological environment were important factors to influence the DOM sources and characteristics.

SAXS Combined with UV-vis Spectroscopy and QELS: Accurate Characterization of Silver Sols Synthesized in Polymer Matrices

The present work demonstrates a validation of small-angle X-ray scattering (SAXS) combining with ultra violet and visible (UV-vis) spectroscopy and quasi-elastic light scattering (QELS) analysis for characterization of silver sols synthesized in polymer matrices. Polymer matrix internal structure and polymer chemical nature actually controlled the sol size characteristics. It was shown that for precise analysis of nanoparticle size distribution these techniques should be used simultaneously. All applied methods were in good agreement for the characterization of size distribution of small particles (less than 60 nm) in the sols. Some deviations of the theoretical curves from the experimental ones were observed. The most probable cause is that nanoparticles were not entirely spherical in form.

Real-time colorimetric detection of DNA methylation of the PAX1 gene in cervical scrapings for cervical cancer screening with thiol-labeled PCR primers and gold nanoparticles

Background

DNA methylation can induce carcinogenesis by silencing key tumor suppressor genes. Analysis of aberrant methylation of tumor suppressor genes can be used as a prognostic and predictive biomarker for cancer. In this study, we propose a colorimetric method for the detection of DNA methylation of the paired box gene 1 (PAX1) gene in cervical scrapings obtained from 42 patients who underwent cervical colposcopic biopsy.

Methods

A thiolated methylation-specific polymerase chain reaction (MSP) primer was used to generate MSP products labeled with the thiol group at one end. After bisulfite conversion and MSP amplification, the unmodified gold nanoparticles (AuNPs) were placed in a reaction tube and NaCl was added to induce aggregation of bare AuNPs without generating polymerase chain reaction products. After salt addition, the color of AuNPs remained red in the methylated PAX1 gene samples because of binding to the MSP-amplified products. By contrast, the color of the AuNP colloid solution changed from red to blue in the non-methylated PAX1 gene samples because of aggregation of AuNPs in the absence of the MSP-amplified products. Furthermore, PAX1 methylation was quantitatively detected in cervical scrapings of patients with varied pathological degrees of cervical cancer. Conventional quantitative MSP (qMSP) was also performed for comparison.

Results

The two methods showed a significant correlation of the methylation frequency of the PAX1 gene in cervical scrapings with severity of cervical cancer (n=42, P<0.05). The results of the proposed method showed that the areas under the receiver operating characteristic curve (AUCs) of PAX1 were 0.833, 0.742, and 0.739 for the detection of cervical intraepithelial neoplasms grade 2 and worse lesions (CIN2+), cervical intraepithelial neoplasms grade 3 and worse lesions (CIN3+), and squamous cell carcinoma, respectively. The sensitivity and specificity for detecting CIN2+ lesions were 0.941 and 0.600, respectively, with a cutoff value of 31.27%. The proposed method also showed superior sensitivity over qMSP methods for the detection of CIN2+ and CIN3+ (0.941 vs 0.824 and 1.000 vs 0.800, respectively). Furthermore, the novel method exhibited higher AUC (0.833) for the detection of CIN2+ than qMSP (0.807).

Conclusion

The results of thiol-labeled AuNP method were clearly observed by the naked eyes without requiring any expensive equipment. Therefore, the thiol-labeled AuNP method could be a simple but efficient strategy for cervical cancer screening.

Application of a Smartphone Metabolomics Platform to the Authentication of Schisandra sinensis

INTRODUCTION

Herbal medicines have been used for a long time all around the world. Since the quality of herbal preparations depends on the source of herbal materials, there has been a strong need to develop methods to correctly identify the origin of materials.

OBJECTIVE

To develop a smartphone metabolomics platform as a simpler and low-cost alternative for the identification of herbal material source.

METHODOLOGY

Schisandra sinensis extracts from Korea and China were prepared. The visible spectra of all samples were measured by a smartphone spectrometer platform. This platform included all the necessary measures built-in for the metabolomics research: data acquisition, processing, chemometric analysis and visualisation of the results. The result of the smartphone metabolomics platform was compared to that of NMR-based metabolomics, suggesting the feasibility of smartphone platform in metabolomics research.

RESULTS

The smartphone metabolomics platform gave similar results to the NMR method, showing good separation between Korean and Chinese materials and correct predictability for all test samples.

CONCLUSION

With its accuracy and advantages of affordability, user-friendliness, and portability, the smartphone metabolomics platform could be applied to the authentication of other medicinal plants. Copyright © 2016 John Wiley & Sons, Ltd.

Synthesis, chiroptical properties and density functional theory calculations of 3,3'-biphenyl-2,2'-bitropone

The synthesis of new bitropone derivatives, namely, 3,3'-biphenyl-2,2'-bitropone and 7,7'-biphenyl-2,2'-bitropone, are reported. Isolation of enantiomers arising from restricted rotation around the C-C bond connecting the tropone moieties was attempted by means of chiral high performance liquid chromatography (HPLC). No separation was obtained for 7,7'-biphenyl-2,2'-bitropone. For 3,3'-biphenyl-2,2'-bitropone, difficulties were encountered because of the low separation factor of the peaks and the presence of a rapid racemization process. However, quantitative chiroptical data on the antipodes were obtained by linking a circular dichroism (CD) spectrometer and a UV-vis spectrophotometric detector in series to the HPLC instrument. The analysis of the CD and UV-vis spectra in terms of absolute conformations was done with the help of theoretical calculations performed at the Density Functional Theory (DFT) level. The most stable conformations of the 3,3'-biphenyl-2,2'-bitropone in its ground state were obtained. Starting from these minimum energy conformations, it was possible to compute theoretical CD and UV absorption spectra that fit well with the experimental ones. From this comparison the absolute configuration to the antipodes was assigned. Finally, the effect of the presence of the two lateral phenyl substituents on the structure of the bitropone and hence on the CD spectrum is discussed.

Using a Matlab implemented algorithm for UV-vis spectral resolution for pKa determination and multicomponent analysis

A Matlab implemented computer code for spectral resolution is presented. The code enables the user to resolve the UV-visible absorption spectrum of a mixture of up to 3 previously known components, to the individual components, thus, evaluating their quantities. The resolving procedure is based on searching the combination of the components which yields the spectrum which is the most similar (minimal RMSE) to the measured spectrum of the mixture. Examples of using the software for pK_a value estimation and multicomponent analysis are presented and other implementations are suggested.