Degradation Characteristics of Cellulose Acetate in Different Aqueous Conditions.

Cellulose acetate (CA) is widely used in cigarette filters and packaging films, but due to its acetylation, it is difficult to degrade in the natural environment, and the problem of pollution has become a serious challenge. Understanding the degradation behavior and performance of CA in different environments is the basis and prerequisite for achieving its comprehensive utilization and developing efficient degradation methods. In this study, we investigated the degradation performance of CA in different aqueous environments to evaluate the effects of pH, salinity and microorganisms on CA degradation. The CA tows and films were immersed in HCl, NaOH solution, river water, seawater or homemade seawater for 16 weeks and the degradation mechanism was investigated by the changes in weight loss rate, degree of substitution, hydrophilicity, molecular structure and surface morphology. The results showed that the degradation of CA tow and film were the fastest in NaOH solution; the weight loss rates after 16 weeks were 40.29% and 39.63%, respectively, followed by HCl solution, and the degradation performance of CA tow was better than that of film. After 16 weeks of degradation in river water, seawater and homemade seawater, all the weight loss rates were less than 3%. In summary, this study illustrated that the environmental acidity, basicity and high concentration of inorganic salts had a critical promotion effect on the non-enzymatic hydrolysis of CA, whereas the number and type of microorganisms were the key factors affecting the biodegradation of CA.

Effects of xanthan gum, konjac glucomannan, and arabinogalactan on the in vitro digestion and fermentation characteristics of biscuits.

Background: Diabetes and its complications have a significant economic impact on individuals and their families. A diet with a low glycemic index (GI) and high fiber content is considered to be associated with the control of blood glucose. Scope and approach: This study explored the effect of polysaccharides, i.e., xanthan gum (BXG), konjac glucomannan (BKG), and arabinogalactan (BAG), on the digestive and prebiotic characteristics of biscuits using a simulated digestion and fermentation model in vitro. Also, the rheological property and structural properties of the polysaccharides were measured to clarify their structure-activity relationships. Key findings and conclusions: During simulated gastrointestinal digestion, the results showed that three types of biscuits containing polysaccharides were low GI foods (estimated GI < 55), in which BAG had the lowest estimated GI value. During in vitro fermentation with diabetic or healthy subjects' fecal microbiota, the three types of biscuits containing polysaccharides (after digestion) decreased the fermentation pH, increased the level of short-chain fatty acids, and modulated the microbiota composition over time. Among the three types of biscuits, BAG increased the abundance of Bifidobacterium and Lactobacillus during fermentation in diabetic and healthy subjects' fecal microbiota. These results showed that the addition of a lower-viscosity polysaccharide (arabinogalactan) may be more beneficial for the blood glucose control of biscuits.

Gut microbial utilization of xylan and its implication in gut homeostasis and metabolic response.

Xylan as the second most abundant indigestible carbohydrate found in nature attracts great interests of researchers, nutritionist and consumers due to its various health benefits. However, accumulated studies indicate the interactions with gut microbiota greatly affect these benefits, and significant progress has been made over the past few years to understand how microbes utilize xylan at gene level. In this review, we focused on gut xylanolytic microbes and xylan's physico-chemical features, summarized the xylanases needed for complete xylan decomposition, their substrate specificity and the presence in gut microbes, as well as microbial degradation of xylan in single strain mode and cooperation mode. Xylan utilization system were discussed with different phyla. Furthermore, the implications on intestinal homeostasis and metabolic response were reviewed with clinical effects emphasized, and highlight is placed on specific gut microbes and the complexity of xylan structure to provide a clue for the inconsistent results in human studies. CHEMICAL COMPOUNDS: xylan; arabinoxylan, glucuronoxylans; glucuronoarabinoxylans; xylo-oligosaccharides; arabinoxylo-oligosaccharides.

A biotin-guided two-photon fluorescent probe for detection of hydrogen peroxide in cancer cells ferroptosis process.

Hydrogen peroxide (H2O2) plays a vital role in organism due to its strong oxidizability, especially in resisting the invasion of pathogens. Cancer cells have abnormal concentrations of hydrogen peroxide due to their disordered reproduction. In complex biological systems, however, conventional fluorescent probes based solely on their fluorescent response to abnormal H2O2 overexpression in cancer cells are not enough to distinguish cancer cells from other unhealthy or immune cells. Therefore, it is necessary to develop other methods to allow the probe to selectively enter the cancer cells and perform fluorescence imaging of the hydrogen peroxide in the cancer cells. Herein, we developed a biotin-guided, two-photon fluorescent probe (BT-HP) for sensitive detection of H2O2 in cancer cells. Through the study on the properties of the probe, it was found that the probe can selectively enter cancer cells. The depth penetration imaging of H2O2 in cancer cells and tumor tissues by two-photon microscope proves the potential of the probe BT-HP as a tumor targeting H2O2 biosensor. The probe was further applied to detect hydrogen peroxide in cancer cells during the ferroptosis process.

A highly tunable stereoselective olefination of semistabilized triphenylphosphonium ylides with N-sulfonyl imines.

The Wittig reaction involving direct olefination of triphenylphosphonium ylides (Ph(3)P horizontal lineCHR) with aldehydes is arguably the most often used method for alkene synthesis, but in general it yields mixtures of Z- and E-alkenes for semistabilized triphenylphosphonium ylides (R = aryl or vinyl). We have developed a simple and efficient protocol to improve the stereoselectivity significantly by replacing the aldehydes used in the Wittig reaction with N-sulfonyl imines, which possess distinct electronic and steric properties relative to aldehydes. A broad range of aromatic, alpha,beta-unsaturated, and aliphatic imines bearing appropriate N-sulfonyl groups smoothly undergo olefination reaction with various benzylidenetriphenylphosphoranes or allylidenetriphenylphosphoranes under mild reaction conditions to afford an array of both Z- and E-isomers of conjugated alkenes in good to excellent yields and with greater than 99:1 stereoselectivity. Moreover, this tunable protocol has been successfully applied to the highly stereoselective synthesis of two anticancer agents, DMU-212 and its Z-isomer.

An expeditious entry to benzylic and allylic sulfones through byproduct-catalyzed reaction of alcohols with sulfinyl chlorides.

In the absence of external catalysts and additives, a broad range of benzylic and allylic alcohols react with various sulfinyl chlorides to afford structurally diversified benzylic and allylic sulfones in moderate to excellent yields, and importantly, a catalysis with byproduct HCl is involved in this new protocol for sulfone synthesis.

Rhodium-catalyzed enantioselective hydrogenation of ß-acylamino nitroolefins: a new approach to chiral ß-amino nitroalkanes.

An efficient and highly enantioselective catalytic asymmetric hydrogenation of ß-acylamino nitroolefins has been realized by using Rh-TangPhos as the catalyst. A series of ß-amino nitroalkane products, which are versatile intermediates in organic synthesis, were obtained with high yield and good enantioselectivity.

Tunable stereoselective alkene synthesis by treatment of activated imines with nonstabilized phosphonium ylides.

A broad range of readily accessible N-sulfonyl imines undergo olefination reaction with nonstabilized phosphonium ylides under mild conditions to afford an array of both Z- and E-isomers of 1,2-disubstituted alkenes, allylic alcohols, and allylic amines in good yields and with greater than 99 : 1 stereoselectivity.