Evaluation of hydroxyl terminated polybutadiene‐isophorone diisocyanate gel formation during crosslinking process

Crosslinking reaction of hydroxyl‐terminated polybutadiene (HTPB)/isophorone di‐isocyanate (IPDI) was monitored by infrared spectroscopy, dynamic mechanical analysis (DMA), swelling measurements, and by relaxation time (T₂) measurements obtained by low‐field NMR technique. Chemical reaction monitored by FTIR shows that urethane bonds were predominantly formed throughout the whole reaction period while DMA and swelling became only effective once the three‐dimensional network was formed. NMR results allow differentiating between relaxation‐processes associated with different fractions of the reactants in the mixture prior to the network formation. The most important finding in this study is that two of the relaxation processes were found to decline whereas a new fraction with a short relaxation time which emerged specifically at an early stage of reaction and progressed along with advancement of the reaction. All results pointed out to a change in the mixture behavior around 30 h of crosslinking reaction at 60°C, reflecting an important restriction in molecules diffusion and mobilities which were attributed to the gel point formation. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Highly dispersed polyamide‐11/halloysite nanocomposites: Thermal,rheological, optical,dielectric, and mechanical properties

Bio‐based polyamide 11 and natural halloysite nanotubes (HNTs) were used for the preparation of PA‐11/HNT nanocomposites with varying nanotubes concentrations by melt extrusion using a masterbatch dilution process. The prepared nanocomposites were analyzed for microstructural changes, transparency, thermal stability, rheological behavior, dielectric, and mechanical properties. The HNT nanotubes are well dispersed in PA‐11 matrix in the studied composition range as shown by microscopy and spectrophotometry. Interestingly, good halloysite dispersion in PA‐11 matrix increases the tensile strength and Young modulus of PA‐11 without sacrificing the ductility. Highly dispersed nanotubes also bring favorable changes in the thermal stability, dielectric, and rheological characteristics of PA‐11. Additionally, glass transition temperature, crystallization temperature, and degree of crystallinity of the nanocomposites tend to increase with increase in nanotubes loading. Thus, PA‐11 can become a tailor‐made material with multifunctional characteristics, thanks to the addition of HNTs. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Flavour compound production by Yarrowia lipolytica, Saccharomyces cerevisiae and Debaryomyces hansenii in a cheese-surface model

A simple cheese model mimicking a cheese surface was developed for the detection of cheese flavour formation of yeasts. A total of 56 flavour compounds were detected by dynamic headspace sampling followed by gas chromatography–mass spectrometry analysis. Yarrowia lipolytica CBS 2075 primarily produced sulphides, furans and short-chain ketones; Saccharomyces cerevisiae D7 primarily produced esters and Debaryomyces hansenii D18335 primarily produced branched-chain aldehydes and alcohols. For several of the detected flavour compounds, an increase in production was observed upon exposure to dairy-relevant environmental stress conditions including high NaCl concentration and low temperature. The predominant yeasts on the cheese surface may be important for development of flavour, and thus the use of yeasts as ripening cultures has the potential to affect the flavour of cheese.     

Post-mortem degradation of myosin heavy chain in intact fish muscle: Effects of pH and enzyme inhibitors

Fish muscle is rapidly degraded during post-mortem storage, due to proteolytic enzymes acting probably both on muscle cells and connective tissue. In this work we have developed a model system which may be used to study the enzymatic degradation occurring in intact post-mortem fish muscle. Degradation of myosin heavy chain (MHC) was monitored in muscle with pH adjusted to 6.05, 6.3 and 6.9 and in the presence of the enzyme inhibitors PMSF, EDTA, phenanthroline, pepstatin A, antipain, E-64 and the cysteine proteinase activator dithiothreithol (DTT). After storage, myofibrillar proteins were isolated and MHC-specific antibodies used to study the degradation in the different samples. MHC from muscle with pH 6.05 and 6.3 was degraded, while no severe degradation was observed at pH 6.9. Introduction of enzyme inhibitors into the muscle tissue clearly showed that mainly cysteine and aspartic proteinases are responsible for the in situ MHC degradation. This is supported by the severe breakdown of MHC in the muscle samples containing DTT.     

Jostling for Position: Optimizing Linker Location in the Design of Estrogen Receptor‐Targeting PROTACs

Estrogen receptor‐α (ER) antagonists have been widely used for breast cancer therapy. Despite initial responsiveness, hormone‐sensitive ER‐positive cancer cells eventually develop resistance to ER antagonists. It has been shown that in most of these resistant tumor cells, the ER is expressed and continues to regulate tumor growth. Recent studies indicate that tamoxifen initially acts as an antagonist, but later functions as an ER agonist, promoting tumor growth. This suggests that targeted ER degradation may provide an effective therapeutic approach for breast cancers, even those that are resistant to conventional therapies. With this in mind, we previously demonstrated that proteolysis targeting chimeras (PROTACs) effectively induce degradation of the ER as a proof‐of‐concept experiment. Herein we further refined the PROTAC approach to target the ER for degradation. The ER‐targeting PROTACs are composed of an estradiol on one end and a hypoxia‐inducing factor 1α (HIF‐1α)‐derived synthetic pentapeptide on the other. The pentapeptide is recognized by an E3 ubiquitin ligase called the von Hippel Lindau tumor suppressor protein (pVHL), thereby recruiting the ER to this E3 ligase for ubiquitination and degradation. Specifically, the pentapeptide is attached at three different locations on estradiol to generate three different PROTAC types. With the pentapeptide linked through the C7α position of estradiol, the resulting PROTAC shows the most effective ER degradation and highest affinity for the estrogen receptor. This result provides an opportunity to develop a novel type of ER antagonist that may overcome the resistance of breast tumors to conventional drugs such as tamoxifen and fulvestrant (Faslodex).     

Combining selected immunomodulatory Propionibacterium freudenreichii and Lactobacillus delbrueckii strains: Reverse engineering development of an anti‐inflammatory cheese

Scope : Inflammatory bowel disease (IBD) constitutes a growing public health concern in western countries. Bacteria with anti‐inflammatory properties are lacking in the dysbiosis accompanying IBD. Selected strains of probiotic bacteria with anti‐inflammatory properties accordingly alleviate symptoms and enhance treatment of ulcerative colitis in clinical trials. Such properties are also found in selected strains of dairy starters such as Propionibacterium freudenreichii and Lactobacillus delbrueckii (Ld). We thus investigated the possibility to develop a fermented dairy product, combining both starter and probiotic abilities of both lactic acid and propionic acid bacteria, designed to extend remissions in IBD patients. Methods and results : We developed a single‐strain Ld‐fermented milk and a two‐strain P. freudenreichii and Ld‐fermented experimental pressed cheese using strains previously selected for their anti‐inflammatory properties. Consumption of these experimental fermented dairy products protected mice against trinitrobenzenesulfonic acid induced colitis, alleviating severity of symptoms, modulating local and systemic inflammation, as well as colonic oxidative stress and epithelial cell damages. As a control, the corresponding sterile dairy matrix failed to afford such protection. Conclusion : This work reveals the probiotic potential of this bacterial mixture, in the context of fermented dairy products. It opens new perspectives for the reverse engineering development of anti‐inflammatory fermented foods designed for target populations with IBD, and has provided evidences leading to an ongoing pilot clinical study in ulcerative colitis patients.