Computational simulations on the taste mechanism of steviol glycosides based on their interactions with receptor proteins.

Steviol glycoside (SG) is a potential natural sugar substitute. The taste of various SG structures differ significantly, while their mechanism has not been thoroughly investigated. To investigate the taste mechanism, molecular docking simulations of SGs with sweet taste receptor TAS1R2 and bitter taste receptor TAS2R4 were conducted. The result suggested that four flexible coils (regions) in TAS1R2 constructed a geometry open pocket in space responsible for the binding of sweeteners. Amino acids that form hydrogen bonds with sweeteners are located in different receptor regions. In bitterness simulation, fewer hydrogen bonds were formed with the increased size of SG molecules. Particularly, there was no interaction between RM and TAS2R4 due to its size, which explains the non-bitterness of RM. Molecular dynamics simulations further indicated that the number of hydrogen bonds between SGs and TAS1R2 was maintained during a simulation time of 50 ns, while sucrose was gradually released from the binding site, leading to the break of interaction. Conclusively, the high sweetness intensity of SG can be attributed to its durative concurrent interaction with the receptor's binding site, and such behavior was determined by the structure feature of SG.

The digestive behavior of pectin in human gastrointestinal tract: a review on fermentation characteristics and degradation mechanism.

Pectin is widely spread in nature and it develops an extremely complex structure in terms of monosaccharide composition, glycosidic linkage types, and non-glycosidic substituents. As a non-digestible polysaccharide, pectin exhibits resistance to human digestive enzymes, however, it is easily utilized by gut microbiota in the large intestine. Currently, pectin has been exploited as a novel functional component with numerous physiological benefits, and it shows a promising prospect in promoting human health. In this review, we introduce the regulatory effects of pectin on intestinal inflammation and metabolic syndromes. Subsequently, the digestive behavior of pectin in the upper gastrointestinal tract is summarized, and then it will be focused on pectin's fermentation characteristics in the large intestine. The fermentation selectivity of pectin by gut bacteria and the effects of pectin structure on intestinal microecology were discussed to highlight the interaction between pectin and bacterial community. Meanwhile, we also offer information on how gut bacteria orchestrate enzymes to degrade pectin. All of these findings provide insights into pectin digestion and advance the application of pectin in human health.

Preparation of lignin containing cellulose nanofibers and its application in PVA nanocomposite films.

Lignin containing cellulose nanofibers (LCNFs) were successfully prepared from wheat straw using an acid hydrotrope of p-toluene sulfonic acid (p-TsOH) combined with ultrasonication. p-TsOH pretreatment was applied below 80 °C to selectively remove hemicellulose and lignin and generate purified cellulose fibers containing approximately 15% lignin. Subsequently, high-intensity ultrasonication was used for <6 min to effectively defibrillate the p-TsOH-pretreated cellulose fibers to nanoscale fibers. AFM and TEM analyses showed that the diameter distribution of the resultant nanofibers decreased with the increase in ultrasonic intensity. The FTIR and XRD results indicated that the molecular structures and cellulose crystallinity were not changed during the ultrasonic process. An amount of 5 wt% of the obtained LCNFs was introduced into a polyvinyl alcohol (PVA) matrix. The resulting nanocomposite products exhibited improved thermal performance and surface properties compared with the pure PVA matrix. The mechanical properties, including the tensile stress and Young's modulus, were enhanced significantly, although the elongation at the break was slightly decreased. PVA composites with the addition of LCNFs are expected to be used in a variety of fields, such as biodegradable plastics, pharmaceutical carrier, filtration media and packaging materials.

Tim-4 expression increases in ischemic stroke patients and is associated with poor outcome.

T cell immunoglobin and mucin domain (Tim)-4 on monocytes is involved in immune regulation. Here, we investigated Tim-4 expression on circulating monocytes and in plasma of ischemic stroke. Tim-4 expression was significantly increased on day 2 and day 5 after stroke. Furthermore, stroke severity was positively correlated with Tim-4 expression on monocytes or in plasma. Increased Tim-4 expression was related to stroke associated with infection (SAI) on day 2. Up-regulated Tim-4 expression on monocytes or in plasma on day 2 was a risk predictor of outcome. Our findings suggest that Tim-4 can act as a prognostic biomarker of ischemic stroke.