Fluorescence Dynamics of Monocyclodextrin– and Bis(thiol‐cyclodextrin)–Coumarin C153 Complexes

The solvation and confinement of coumarin C153 within supramolecular host/guest complexes based on β‐cyclodextrin (β‐CD) and 6‐deoxy‐6‐thio‐β‐cyclodextrin (β‐CD‐SH) in water are studied by fluorescence spectroscopy. For β‐CD/C153, the 1:1 complex is proposed, and for β‐CD‐SH/C153 both the 1:1 and 2:1 complexes are believed to be formed. The 2:1 β‐CD‐SH/C153 complex has an association constant of 4.2×10⁵ M ^?1 and a C153 population of 82 %, which are interestingly high values, indicating that the proposed β‐CD‐SH dimers structure are connected by covalent disulfide bonds; this is supported by mass spectrometry. Solvation related to fast hydrogen‐bond rearrangement as a part of fluorescence relaxation is determined by the ultrafast components of time‐resolved spectroscopy to be 3 and 7 ps for the 1:1 β‐CD/C153 and 2:1 β‐CD‐SH/C153 complexes, respectively.     

Effect of indium doping on thermal stability and dielectric property in sodium beta alumina solid electrolyte

Journal of Solid State Electrochemistry - We report the effect of indium doping on thermal stability and ionic conductivity of beta alumina NaInxAl11-xO17 solid electrolyte which is synthesized by...     

Effect of positron density and temperature on the electron acoustic waves in a magnetized dissipative plasma

Zakharov–Kuznetsov–Burgers (ZKB) equation is derived for electron acoustic shock waves in magnetized e–p–i plasma. In the present model, magnetized plasma containing two electron population with kappa distributed positrons has been considered. The propagation characteristics of three dimensional electron acoustic (EA) shock waves have been studied under the influence of magnetic field. Our present plasma model supports the negative potential shocks. Combined action of dissipation (η), superthermality (κ), concentration of positrons (β), temperature ratio of cold electrons to positrons (σ), and magnetic field (ω_c) significantly modify the properties of EA shock waves. The width and amplitude of the shock structures are modified by various physical parameters. It is found that shock wave width decreases with increase in β, η₀, and ω_c whereas it becomes wider for κ and σ. Further, potential of the shock wave decreases as one departs away from superthermal distribution.     

Magnesium deposition in brain of pregnant patients administered intramuscular magnesium sulphate

We present three cases of T1 hyperintense signal in the MRI scans of the brains of pregnant patients who were administered magnesium sulphate intramuscularly for control of hypertension during eclampsia. The increase in signal is symmetric and is seen in the globus pallidi of these patients. We postulate it to be secondary to deposition of magnesium in the brain parenchyma. The signal intensity was found to be directly varying according to the level of magnesium in the blood. It decreased over a period of time coming to normalcy after approximately 6 months. To the best of our knowledge, this is the first case report which has documented this finding. It has to be determined whether deposition of magnesium in the brain parenchyma could have implications in the use of magnesium sulphate in pregnant patients.     

Ultraviolet photocatalytic degradation of cholesterol on TiO2: secondary ion mass spectrometry

Cholesterol (C₂₇H₄₆O stated as M) is used as a model of bio‐organic contamination, because this compound is in almost every living organism, and its photocatalytic degradation on titanium oxide (TiO₂) surface with UV exposure is investigated. Secondary ion mass spectrometry as a surface‐sensitive technique is suited to study this degradation process with focus on intermediates. A fragment of M–OH represents the intact molecule of cholesterol and provides its relative concentration on the surface. The intensity of M–OH decreases after 24‐h UV irradiation, and the level of degradation is 89% with the pseudo‐first kinetic constant of 0.0207 min^?1 within 2 h. A fragment of MO–H represents an intermediate as one of the cholesterol oxidation products. The irradiation from a bottom in comparison with a top reveals the differences in the mechanism of the intermediate formation through the intensity and the kinetics with values of factor of 1/3 and 30 min, respectively. The roles of electrons and holes, primarily generated in TiO₂ by UV, and also of superoxide anion radical and hydroxyl radical, as the secondary reactive species, are discussed to illustrate the bottom/top mechanisms. Copyright © 2016 John Wiley & Sons, Ltd.     

Preconcentration based on paramagnetic microparticles for the separation of sarcosine using hydrophilic interaction liquid chromatography coupled with coulometric detection

Sarcosine has been identified as a potential prostate cancer marker. To provide determination of this compound, a number of methods are developing. In this study, we optimized a method for its separation by hydrophilic interaction LC with electrochemical detection (ED). Due to the fact that mobile phases commonly used for this type of separation altered the LODs measured by electrochemical detectors, we applied postcolumn dosing of buffer suitable for ED. The optimized conditions were mobile phase A acetonitrile, mobile phase B water in the ratio A/B 70:30, with postcolumn addition of mobile phase C (200 mM phosphate buffer pH 9). The optimal mixing ratio was A + B/C 1:1 with a flow rate of 0.80 mL/min (0.40 + 0.40 mL/min) and detection potential of 1000 mV. Due to the optimization of the parameters for effective separation, which had to meet the optimal parameters of ED, we reached a good resolution for separation also with a good LOD (100 nM). In addition, we successfully carried out sarcosine analysis bound on our modified paramagnetic microparticles with the ability to preconcentrate sarcosine isolated from artificial urine.     

Chemical Composition Assessment of Structural Parts (Seeds,Peel, Pulp) of Physalis alkekengi L. Fruits

In recent years there has been an extensive search for nature-based products with functional potential. All structural parts of Physalis alkekengi (bladder cherry), including fruits, pulp, and less-explored parts, such as seeds and peel, can be considered sources of functional macro- and micronutrients, bioactive compounds, such as vitamins, minerals, polyphenols, and polyunsaturated fatty acids, and dietetic fiber. The chemical composition of all fruit structural parts (seeds, peel, and pulp) of two phenotypes of P. alkekengi were studied. The seeds were found to be a rich source of oil, yielding 14–17%, with abundant amounts of unsaturated fatty acids (over 88%) and tocopherols, or vitamin E (up to 5378 mg/kg dw; dry weight). The predominant fatty acid in the seed oils was linoleic acid, followed by oleic acid. The seeds contained most of the fruit’s protein (16–19% dw) and fiber (6–8% dw). The peel oil differed significantly from the seed oil in fatty acid and tocopherol composition. Seed cakes, the waste after oil extraction, contained arginine and aspartic acid as the main amino acids; valine, phenylalanine, threonine, and isoleucine were present in slightly higher amounts than the other essential amino acids. They were also rich in key minerals, such as K, Mg, Fe, and Zn. From the peel and pulp fractions were extracted fruit concretes, aromatic products with specific fragrance profiles, of which volatile compositions (GC-MS) were identified. The major volatiles in peel and pulp concretes were β-linalool, α-pinene, and γ-terpinene. The results from the investigation substantiated the potential of all the studied fruit structures as new sources of bioactive compounds that could be used as prospective sources in human and animal nutrition, while the aroma-active compounds in the concretes supported the plant’s potential in perfumery and cosmetics.     

Surface Nanostructures Composed of Thiolated Cyclodextrin/Au and Fe Species: Gas‐ and Liquid‐Phase Preparation

Supramolecular surface nanostructures have application potential as functional devices. The complex combination of thiolated cyclodextrin, chemisorbed on an Au surface (Au‐S‐CD), with deposited Fe species is studied by secondary ion mass spectrometry. The Fe species are prepared by pulsed laser ablation in water and thermal effusion in vacuum. Using laser ablation in water, the solution of Fe species is dropped on Au‐S‐CD, where mass peaks at 1227 m/z, 1243 m/z, and 1260 m/z are observed and assigned to C₄₂H₆₈O₃₄SNa‐Fe⁺, C₄₂H₆₈O₃₄SK‐Fe⁺ together with C₄₂H₆₈O₃₄SNa‐FeO⁺, and C₄₂H₆₈O₃₄SK‐FeO⁺, respectively. On the other hand, laser ablation directly linked to the Au‐S‐CD surface results in desorption of CD‐S. Thermal effusion, even with a cooled surface, was negative with respect to the complex observation. Laser ablation results in the formation of a supramolecular host–guest complex of the form Au‐S‐CD‐Fe, and in the formation of an adduct of the form Au‐S‐CD‐FeO.     

Tryptophan in Multicomponent Petasis Reactions for Peptide Stapling and Late-Stage Functionalisation

Peptide stapling is a robust strategy for generating enzymatically stable, macrocyclic peptides. The incorporation of biologically relevant tags (such as cell-penetrating motifs or fluorescent dyes) into peptides, while preserving their binding interactions and enhancing their stability, is highly sought after. Despite the unique opportunities offered by tryptophan‘s indole scaffold for targeted functionalisation, its utilisation in peptide stapling has been limited as compared to other amino acids. Herein, we present an approach for peptide stapling using the tryptophan-mediated Petasis reaction. This method enables the synthesis of both stapled and labelled peptides and is applicable to both solution and solid-phase synthesis. Importantly, the use of the Petasis reaction in combination with tryptophan facilitates the formation of stapled peptides in a straightforward, multicomponent fashion, while circumventing the formation of undesired by-products. Furthermore, this approach allows for efficient and diverse late-stage peptide modifications, thereby enabling rapid production of numerous conjugates for biological and medicinal applications.     

Determination of phenolic compounds and hydroxymethylfurfural in meads using high performance liquid chromatography with coulometric-array and UV detection

The objective of this study was the determination of 25 phenolic compounds in different mead samples (honeywines) using high performance liquid chromatography (HPLC) with coulometric-array detection and in case of hydroxymethylfurfural with UV detection. Our method was optimized in respect to both the separation selectivity of individual phenolic compounds and the maximum sensitivity with the electrochemical detection. The method development included the optimization of mobile phase composition, the pH value, conditions of the gradient elution and the flow rate using a window-diagram approach. The developed method was used for the determination of limits of detection and limits of quantitation for individual compounds. The linearity of calibration curves, accuracy and precision (intra- and inter-day) at three concentration levels (low, middle and high concentration range) were verified. Mead samples were diluted with the mobile phase at 1:1 to 1:50 ratio depending on the concentration and filtered through a PTFE filter without any other sample pre-treatment. Phenolic compounds concentration was determined in 50 real samples of meads and correlated with meads composition and hydroxymethylfurfural concentration. The most frequently occurred compounds were protocatechuic acid and vanillic acid (both of them were present in 98% samples), the least occurred compounds were (+)-catechin (10% samples) and sinapic acid (12% samples). Vanillin and ethylvanillin, which are used as artificial additives for the taste improvement, were found in 60% and 42% samples, respectively. Hydroxymethylfurfural concentration, as an indicator of honey quality, was in the range from 2.47 to 158 mg/L. Our method is applicable for the determination of 25 phenolic compounds in mead, honey and related natural samples.