Polymer Microcapsules with Carbohydrate‐Sensitive Properties

Carbohydrate‐sensitive polymer multilayers are assembled onto flat substrates and colloidal CaCO₃ particles via reversible covalent ester formation between the polysaccharide mannan and phenylboronic acid moieties grafted onto poly(acrylic acid) (PAA). The resulting multilayer films are sensitive to several carbohydrates, and show the highest sensitivity to fructose. The response to carbohydrates arises from the competitive binding of small molecular weight sugars and mannan to boronic acid groups within the films, and is observed as a rapid dissolution of the multilayers upon contact with a sugar‐containing solution above a critical concentration. In addition, carbohydrate‐sensitive multilayer capsules are prepared, and their sugar‐dependent stability is investigated by following the release of encapsulated tetramethylrhodamine isothiocyanate‐bovine serum albumin (TRITC‐BSA).     

Norepinephrine Inhibits Lipopolysaccharide-Stimulated TNF-α but Not Oxylipin Induction in n-3/n-6 PUFA-Enriched Cultures of Circumventricular Organs

Sensory circumventricular organs (sCVOs) are pivotal brain structures involved in immune-to-brain communication with a leaky blood–brain barrier that detect circulating mediators such as lipopolysaccharide (LPS). Here, we aimed to investigate the potential of sCVOs to produce n-3 and n-6 oxylipins after LPS-stimulation. Moreover, we investigated if norepinephrine (NE) co-treatment can alter cytokine- and oxylipin-release. Thus, we stimulated rat primary neuroglial sCVO cultures under n-3- or n-6-enriched conditions with LPS or saline combined with NE or vehicle. Supernatants were assessed for cytokines by bioassays and oxylipins by HPLC-MS/MS. Expression of signaling pathways and enzymes were analyzed by RT-PCR. Tumor necrosis factor (TNF)α bioactivity and signaling, IL-10 expression, and cyclooxygenase (COX)2 were increased, epoxide hydroxylase (Ephx)2 was reduced, and lipoxygenase 15-(LOX) was not changed by LPS stimulation. Moreover, LPS induced increased levels of several n-6-derived oxylipins, including the COX-2 metabolite 15d-prostaglandin-J2 or the Ephx2 metabolite 14,15-DHET. For n-3-derived oxylipins, some were down- and some were upregulated, including 15-LOX-derived neuroprotectin D1 and 18-HEPE, known for their anti-inflammatory potential. While the LPS-induced increase in TNFα levels was significantly reduced by NE, oxylipins were not significantly altered by NE or changes in TNFα levels. In conclusion, LPS-induced oxylipins may play an important functional role in sCVOs for immune-to-brain communication.     

Effect of thermal oxidative ageing on the morphology of natural rubber networks as viewed by ESR

The change of network morphology of unfilled sulfur crosslinked natural rubber exposed to thermal oxidative ageing has been studied. Three model networks with different sulfur contents (efficient network, semi‐efficient and conventional vulcanizate) have been analysed by applying spin probe ESR, equilibrium swelling measurements and mechanical measurements. By combining the density distribution deduced from the complex ESR spectra and the equilibrium swelling density, it is shown that the major network changes occur in the networks with predominantly polysulfidic bonds (conventional network) after 96 h of ageing at 373 K. The effect of ageing on the network with predominantly monosulfidic bonds is much less pronounced. Both effects (main chain scission and additional local crosslinking) have been analysed in the course of prolonged ageing up to 240 h. A correlation between network structure and its mechanical performance is established. © 2000 Society of Chemical Industry     

Electronic Nose Technology in Quality Assessment: Predicting Volatile Composition of Danish Blue Cheese During Ripening

This work describes for the 1st time the use of an electronic nose (e‐nose) for the determination of changes of blue cheeses flavor during maturation. Headspace analysis of Danish blue cheeses was made for 2 dairy units of the same producer. An e‐nose registered changes in cheeses flavor 5, 8, 12, and 20 wk after brining. Volatiles were collected from the headspace and analyzed by gas chromatography‐mass spectrometry (GC‐MS). Features from the chemical sensors of the e‐nose were used to model the volatile changes by multivariate methods. Differences registered during ripening of the cheeses as well as between producing units are described and discussed for both methods. Cheeses from different units showed significant differences in their e‐nose flavor profiles at early ripening stages but with ripening became more and more alike. Prediction of the concentration of 25 identified aroma compounds by e‐nose features was possible by partial least square regression (PLS‐R). It was not possible to create a reliable predictive model for both units because cheeses from 1 unit were contaminated by Geotrichum candidum, leading to unstable ripening patterns. Correction of the e‐nose features by multiple scatter correction (MSC) and mean normalization (MN) of the integrated GC areas made correlation of the volatile concentration to the e‐nose signal features possible. Prediction models were created, evaluated, and used to reconstruct the headspace of unknown cheese samples by e‐nose measurements. Classification of predicted volatile compositions of unknown samples by their ripening stage was successful at a 78% and 54% overall correct classification for dairy units 1 and 2, respectively. Compared with GC‐MS, the application of the rapid and less demanding e‐nose seems an attractive alternative for this type of investigation.     

Unmodified and esterified Kraft lignin‐filled polyethylene composites: Compatibilization by free‐radical grafting

In this study, the effectiveness of free‐radical grafting as a compatibilization method applied to composites containing Kraft lignin (KL) and esterified lignin was comparatively investigated. Maleated lignin (ML) was first obtained via esterification of KL with maleic anhydride. KL and ML were respectively incorporated into high density polyethylene (HDPE) up to 60% wt and dicumyl peroxide was used as a free‐radical generator. The influence of lignin esterification and free‐radical grafting on the morphological, mechanical, and thermal properties of lignin‐based composites was studied. The incorporation of lignins into HDPE resulted in poor mechanical strength because of low compatibility. Morphological and mechanical evidences indicate improved compatibility between lignins and HDPE following free‐radical grafting. The free‐radical scavenging properties of KL allowed better compatibilization of KL‐based composites compared with ML‐based composites. In addition, thermal analysis results showed that free‐radical grafting increases the thermal stability of ML‐based composites. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41484.     

DNA G-Quadruplexes Contribute to CTCF Recruitment

G-quadruplex (G4) sites in the human genome frequently colocalize with CCCTC-binding factor (CTCF)-bound sites in CpG islands (CGIs). We aimed to clarify the role of G4s in CTCF positioning. Molecular modeling data suggested direct interactions, so we performed in vitro binding assays with quadruplex-forming sequences from CGIs in the human genome. G4s bound CTCF with Kd values similar to that of the control duplex, while respective i-motifs exhibited no affinity for CTCF. Using ChIP-qPCR assays, we showed that G4-stabilizing ligands enhance CTCF occupancy at a G4-prone site in STAT3 gene. In view of the reportedly increased CTCF affinity for hypomethylated DNA, we next questioned whether G4s also facilitate CTCF recruitment to CGIs via protecting CpG sites from methylation. Bioinformatics analysis of previously published data argued against such a possibility. Finally, we questioned whether G4s facilitate CTCF recruitment by affecting chromatin structure. We showed that three architectural chromatin proteins of the high mobility group colocalize with G4s in the genome and recognize parallel-stranded or mixed-topology G4s in vitro. One of such proteins, HMGN3, contributes to the association between G4s and CTCF according to our bioinformatics analysis. These findings support both direct and indirect roles of G4s in CTCF recruitment.     

Isotope-Guided Metabolomics Reveals Divergent Incorporation of Valine into Different Flavor Precursor Classes in Chives

Plants of the genus Allium such as chives, onions or garlic produce S-alk(en)yl cysteine sulfoxides as flavor precursors. Two major representatives are S-propenyl cysteine sulfoxide (isoalliin) and S-propyl cysteine sulfoxide (propiin), which only differ by a double bond in the C₃ side chain. The propenyl group of isoalliin is derived from the amino acid valine, but the source of the propyl group of propiin remains unclear. Here, we present an untargeted metabolomics approach in seedlings of chives (Allium schoenoprasum) to track mass features containing sulfur and/or ¹³C from labeling experiments with valine-¹³C₅ guided by their isotope signatures. Our data show that propiin and related propyl-bearing metabolites incorporate carbon derived from valine-¹³C₅, but to a much lesser extent than isoalliin and related propenyl compounds. Our findings provide new insights into the biosynthetic pathways of flavor precursors in Allium species and open new avenues for future untargeted labeling experiments.     

Activation Profile of TAS2R2, the 26th Human Bitter Taste Receptor

Scope

To avoid ingestion of potentially harmful substances, humans are equipped with about 25 bitter taste receptor genes (TAS2R) expressed in oral taste cells. Humans exhibit considerable variance in their bitter tasting abilities, which are associated with genetic polymorphisms in bitter taste receptor genes. One of these variant receptor genes, TAS2R2, is initially believed to represent a pseudogene. However, TAS2R2 exists in a putative functional variant within some populations and can therefore be considered as an additional functional bitter taste receptor.

Methods and results

To learn more about the function of the experimentally neglected TAS2R2, a functional screening with 122 bitter compounds is performed. The study observes responses with eight of the 122 bitter substances and identifies the substance phenylbutazone as a unique activator of TAS2R2 among the family of TAS2Rs, thus filling one more gap in the array of cognate bitter substances.

Conclusions

The comprehensive characterization of the receptive range of TAS2R2 allows the classification into the group of TAS2Rs with a medium number of bitter agonists. The variability of bitter taste and its potential influences on food choice in some human populations may be even higher than assumed.