Self‐assembled monolayers of mercaptosuccinic acid monolayers on silver and gold surfaces designed for protein binding. Part II: vibrational spectroscopy studies on cytochrome c immobilization

An attempt has been made for using MSA‐modified electrodes as linkage monolayers for electrostatic and covalent binding of cytochrome c (Cc). For MSA monolayers grown from an aqueous solution on Ag, attachment of Cc in its native state is proved in the case of covalent bonding. Electrostatic immobilization of Cc at pH 7 results in presence of at least some amount of Fe²⁺ high‐spin configuration and/or Fe³⁺ oxidation state. Native protein Fe²⁺ low‐spin state of Cc is observed after applying a negative potential to the Ag electrode. The influence of the solvent used for the preparation of the MSA monolayer and thiol surface coverage of the Ag surface was studied. It was shown that the key factor to obtain the native structure of Cc is the successful blocking of the metal surface by the MSA linking layer. IRRAS measurements of MSA on monocrystalline gold (111) at neutral pH confirm the successful electrostatic Cc immobilization, which preserves the Fe²⁺ oxidation state of the chromophore on this substrate. Copyright © 2007 John Wiley & Sons, Ltd.     

Chiroptical Properties – Structure Relationship in Bicyclic Isoxazolidin‐5‐one Derivatives

The relationship between chiroptical properties of substituted bicyclic isoxazolidin‐5‐one derivatives and their molecular structures was investigated. The chromophoric system in isoxazolidinones was found to be nonplanar with a shallow pyramidal configuration at the N‐atom. The deviation from planarity can be attributed to the strain imposed by the bicyclic skeleton. Due to the nonplanarity, the isoxazolidinone system becomes inherently dissymmetric, which is supported by the high magnitude of the CD band occurring around 210 nm. In addition, the helicity of lactone moiety in investigated bicyclic isoxazolidinones is controlled by the absolute configuration at C(6). On this basis, a helicity rule correlating a positive (negative) helicity expressed by the OC(8) O(9) N(1) torsional angle with a positive (negative) sign of the CD band around 210 nm was formulated.     

Effect of Vitamin C Source on Its Stability during Storage and the Properties of Milk Fermented by Lactobacillus rhamnosus

The enrichment of commonly consumed foods with bioactive components might be helpful in promoting health and reducing the risk of disease, so the enrichment of probiotic fermented milk with vitamin C can be considered appropriate. The effect of vitamin C addition depends on the source of origin (rosehip, acerola and ascorbic acid in powder form) on the growth and survival of Lactobacillus rhamnosus and the quality of fermented milk on the 1st and 21st day of storage was analyzed. The pH, total acidity, vitamin C, syneresis, color, texture profile and numbers of bacterial cells in fermented milk were determined. The organoleptic evaluation was also performed. The degradation of vitamin C in milk was shown to depend on its source. The lowest reduction of vitamin C was determined in milk with rosehip. The least stable was vitamin C naturally found in control milk. The addition of rosehip and acerola decreased syneresis and lightness of milk color, increasing the yellow and red color proportion. In contrast, milk with ascorbic acid was the lightest during the whole experimental period and was characterized by a very soft gel. The growth of Lactobacillus rhamnosus during fermentation was most positively affected by the addition of rosehip. However, the best survival of Lactobacillus rhamnosus was demonstrated in milk with acerola. On the 21st day of storage, the number of L. rhamnosus cells in the control milk and the milk with vitamin C was >8 log cfu g⁻¹, so these milks met the criterion of therapeutic minimum. According to the assessors, the taste and odor contributed by the addition of rosehip was the most intense of all the vitamin C sources used in the study.     

Discrimination of Adulterated Ginkgo Biloba Products Based on 2T2D Correlation Spectroscopy in UV-Vis Range

Ginkgo biloba is a popular medicinal plant widely used in numerous herbal products, including food supplements. Due to its popularity and growing economic value, G. biloba leaf extract has become the target of economically motivated adulterations. There are many reports about the poor quality of ginkgo products and their adulteration, mainly by adding flavonols, flavonol glycosides, or extracts from other plants. In this work, we developed an approach using two-trace two-dimensional correlation spectroscopy (2T2D COS) in UV-Vis range combined with multilinear principal component analysis (MPCA) to detect potential adulteration of twenty G. biloba food supplements. UV-Vis spectral data are obtained for 80% methanol and aqueous extracts in the range of 245–410 nm. Three series of two-dimensional correlation spectra were interpreted by visual inspection and using MPCA. The proposed relatively quick and straightforward approach successfully differentiated supplements adulterated with rutin or those lacking ginkgo leaf extract. Supporting information about adulteration was obtained from the difference between the DPPH radical scavenging capacity of both extracts and from chromatographic (HPLC-DAD) fingerprints of methanolic samples.     

Investigation of the reaction of N-substituted indolylborates: Palladium catalyzed cross-coupling reactions and intramolecular alkyl migration reactions

The palladium catalyzed cross-coupling reaction of indolylborates with various N-protecting groups was investigated, where N-Methyl, N-methoxy, and N-tert-butoxycarbonyl groups were found to be useful. However, triethyl(1-methoxymethylindol-2-yl)borate could not be used for this reaction. It was also found that the alkyl migration reaction of trialkyl(1-methoxymethylindol-2-yl)borate produced 2-alkyl-1-methyl-indole accompanied by the unexpected reduction of 1-methoxymethyl group to 1-methyl group.     

Rapid and Accurate Approach for Honeybee Pollen Analysis Using ED-XRF and FTIR Spectroscopy

Since honeybee pollen is considered a “perfectly complete food” and is characterized by many beneficial properties (anti-inflammatory, antioxidant, anti-bacterial, etc.), it has begun to be used for therapeutic purposes. Consequently, there is a high need to develop methods for controlling its composition. A thorough bee pollen analysis can be very informative regarding its safety for consumption, the variability of its composition, its biogeographical origin, or harvest date. Therefore, in this study, two reliable and non-destructive spectroscopy methods, i.e., ED-XRF and ATR–FTIR, are proposed as a fast approach to characterize bee pollen. The collected samples were derived from apiaries located in west-central Poland. Additionally, some commercially available samples were analyzed. The applied methodology was optimized and combined with sophisticated chemometric tools. Data derived from IR analyses were also subjected to two-dimensional correlation spectroscopy. The developed ED-XRF method allowed the reliable quantification of eight macro- and micro-nutrients, while organic components were characterized by IR spectroscopy. Principal component analysis, cluster analysis, and obtained synchronous and asynchronous maps allowed the study of component changes occurring dependently on the date and location of harvest. The proposed approach proved to be an excellent tool to monitor the variability of the inorganic and organic content of bee pollen.     

2,3‐Dihydro‐1,3‐benzothiazol‐2‐iminium hydrogen oxydiacetate: a combined structural and theoretical study

In the title compound, C₇H₇N₂S⁺·C₄H₅O₅⁻, the ions are connected by N—H...O hydrogen bonds. The hydrogen oxydiacetate residues are linked together by O—H...O hydrogen bonds disordered about centres of inversion into hydrogen‐bonded ribbon layers crosslinked by weak C—H...O and stacking interactions. The cation exists mainly in the 2,3‐dihydro‐1,3‐benzothiazol‐2‐iminium form, with a small participation of the 2‐aminobenzothiazolium form, based on the structural data and quantum mechanical calculations. This study provides structural insights relevant to the biochemical activity of benzothiazole molecules.     

Adjusting the Structure of β-Cyclodextrin to Improve Complexation of Anthraquinone-Derived Drugs

β-Cyclodextrin (CD) derivatives containing an aromatic triazole ring were studied as potential carriers of the following drugs containing an anthraquinone moiety: anthraquinone-2-sulfonic acid (AQ2S); anthraquinone-2-carboxylic acid (AQ2CA); and a common anthracycline, daunorubicin (DNR). UV-Vis and voltammetry measurements were carried out to determine the solubilities and association constants of the complexes formed, and the results revealed the unique properties of the chosen CDs as effective pH-dependent drug complexing agents. The association constants of the drug complexes with the CDs containing a triazole and lipoic acid (βCDLip) or galactosamine (βCDGAL), were significantly larger than that of the native βCD. The AQ2CA and AQ2S drugs were poorly soluble, and their solubilities increased as a result of complex formation with βCDLip and βCDGAL ligands. AQ2CA and AQ2S are negatively charged at pH 7.4. Therefore, they were less prone to form an inclusion complex with the hydrophobic CD cavity than at pH 3 (characteristic of gastric juices) when protonated. The βCDTriazole and βCDGAL ligands were found to form weaker inclusion complexes with the positively charged drug DNR at an acidic pH (pH 5.5) than in a neutral medium (pH 7.4) in which the drug dissociates to its neutral, uncharged form. This pH dependence is favorable for antitumor applications.     

Covariant formulation of BPS black holes and the scalar weak gravity conjecture

We find through a systematic analysis that all but 29,223 of the 473.8 million 4D reflexive polytopes found by Kreuzer and Skarke have a 2D reflexive subpolytope. Such a subpolytope is generally associated with the presence of an elliptic or genus one fibration in the corresponding birational equivalence class of Calabi-Yau threefolds. This extends the growing body of evidence that most Calabi-Yau threefolds have an elliptically fibered phase.     

Nanofibers as optical sensors for model VOCs dispersed in aqueous phase

Nanofibers mats, prepared from poly(vinyl chloride) (PVC) containing dispersed dye Nile red (NR) were applied in a proof of concept study as optical sensors for Volatile Organic Compounds (VOCs) dispersed in an aqueous phase. Benefiting from the solubility of the dye, and in some cases, also of the polymer in model solvents belonging to the group of VOCs, an increase of emission was observed for increasing solvent concentration in the sample. The optical signal formation was observed regardless if only the dye or both dye and PVC were soluble in the tested solvent. In both cases, high sensitivity emission increases for increasing VOCs present in the aqueous phase were observed within the range of concentration of model analytes: from 200 ppm of m-xylene or from 300 ppm of styrene, to up to ca 1500 ppm. The obtained higher detection limit was lower compared to films of PVC containing the dye due to the lower availability of the material to be dissolved by analyte – solvent. The large surface area of nanofibers was useful in the detection, leading to higher signal changes compared to films.