A study has been conducted on the sintering of a ceramic ferrite having the composition (Cu0.25Ni0.25Zn0.50)Fe2O4. The study analyzes the evolution of ferrite relative to density and microstructure with peak sintering temperature and dwell time at peak temperature. The densification and grain-growth rates are correlated with average grain size, relative density, and temperature. Corresponding rate-controlling diffusion mechanisms are proposed. 相似文献
Considering nearly 80 years of research regarding one of the enzymes responsible for catalyzing the formation of pigments in higher animals, plants, fungi and bacteria, this review will focus on collecting and categorizing the existing information about polyphenol oxidase (PPO) in fruits, with particular emphasis on the information in relation to avocado, which is one of the hardiest species in terms of inactivation, has documented dual activity (EC 1.14.18.1/EC 1.10.3.1), and represents one of the oldest challenges for food science research and fruit processors.
It is expected that this review will contribute to the further development of the field by highlighting the questions that have arisen during the characterization of PPO, the progress that has been made and the questions that remain today, in addition to new methodologies that are being applied to study this system. Holistic methodologies offer unexplored potential for advancing our understanding of the complex phenomena that govern PPO activity in fruits, because these methodologies will enable the characterization of this family of enzymes in all of its complexity. Subsequently, it will be possible to develop better techniques for controlling enzymatic browning in this valuable fruit. 相似文献
Araucaria (Araucaria araucana) is a conifer tree, endemic of Chile. The seed of this tree, named piñon are composed principally of starch. In this work, piñon seeds and the starch isolated from them were evaluated. The piñon seeds are composed of starch (64%), dietary fibre (25%), total sugar (7%) and very low concentrations of phenolic compounds, lipids, proteins and crude fibre. The process performed to isolate the starch from piñon was simple and easy to realize at laboratory scale, with a yield of 36%. Starch represents a 77% of the isolated starch. The amylose content was 42%. Lipids, protein and crude fibre were very low. The starch hydration properties increased with the temperature. In the 6% suspension of starch, viscosity increases during the cooling period. The starch granules of piñon were small and round shaped. The aspects evaluated in this research, suggests that piñon seeds can be considered an interesting new starch source for the food industry. 相似文献
Centrins are a family of small, EF hand-containing proteins that are found in all eukaryotes and are often complexed with centrosome-related structures. Since their discovery, centrins have attracted increasing interest due to their multiple, diverse cellular functions. Centrins are similar to calmodulin (CaM) in size, structure and domain organization, although in contrast to CaM, the majority of centrins possess at least one calcium (Ca2+) binding site that is non-functional, thus displaying large variance in Ca2+ sensing abilities that could support their functional versatility. In this review, we summarize current knowledge on centrins from both biophysical and structural perspectives with an emphasis on centrin-target interactions. In-depth analysis of the Ca2+ sensing properties of centrins and structures of centrins complexed with target proteins can provide useful insight into the mechanisms of the different functions of centrins and how these proteins contribute to the complexity of the Ca2+ signaling cascade. Moreover, it can help to better understand the functional redundancy of centrin isoforms and centrin-binding proteins. 相似文献
Angiopoietin-like protein 8 (ANGPTL8) is an hepatokine altered in several metabolic conditions, such as obesity, type 2 diabetes, dyslipidemia and nonalcoholic fatty liver disease (NAFLD). We sought to explore whether ANGPTL8 is involved in NAFLD amelioration after bariatric surgery in experimental models and patients with severe obesity. Plasma ANGPTL8 was measured in 170 individuals before and 6 months after bariatric surgery. Hepatic ANGPTL8 expression was evaluated in liver biopsies of patients with severe obesity undergoing bariatric surgery with available liver pathology analysis (n = 75), as well as in male Wistar rats with diet-induced obesity subjected to sham operation, sleeve gastrectomy or Roux-en-Y gastric bypass (RYGB) (n = 65). The effect of ANGPTL8 on lipogenesis was assessed in human HepG2 hepatocytes under palmitate-induced lipotoxic conditions. Plasma concentrations and hepatic expression of ANGPTL8 were increased in patients with obesity-associated NAFLD in relation to the degree of hepatic steatosis. Sleeve gastrectomy and RYGB improved hepatosteatosis and reduced the hepatic ANGPTL8 expression in the preclinical model of NAFLD. Interestingly, ANGPTL8 inhibited steatosis and expression of lipogenic factors (PPARG2, SREBF1, MOGAT2 and DGAT1) in palmitate-treated human hepatocytes. Together, ANGPTL8 is involved in the resolution of NAFLD after bariatric surgery partially by the inhibition of lipogenesis in steatotic hepatocytes. 相似文献
Despite some progress, the overall survival of patients with glioblastoma (GBM) remains extremely poor. In this context, there is a pressing need to develop innovative therapy strategies for GBM, namely those based on nanomedicine approaches. Towards this goal, we have focused on nanoparticles (AuNP-SP and AuNP-SPTyr8) with a small gold core (ca. 4 nm), carrying DOTA chelators and substance P (SP) peptides. These new SP-containing AuNPs were characterized by a variety of analytical techniques, including TEM and DLS measurements and UV-vis and CD spectroscopy, which proved their high in vitro stability and poor tendency to interact with plasma proteins. Their labeling with diagnostic and therapeutic radionuclides was efficiently performed by DOTA complexation with the trivalent radiometals 67Ga and 177Lu or by electrophilic radioiodination with 125I of the tyrosyl residue in AuNP-SPTyr8. Cellular studies of the resulting radiolabeled AuNPs in NKR1-positive GBM cells (U87, T98G and U373) have shown that the presence of the SP peptides has a crucial and positive impact on their internalization by the tumor cells. Consistently, 177Lu-AuNP-SPTyr8 showed more pronounced radiobiological effects in U373 cells when compared with the non-targeted congener 177Lu-AuNP-TDOTA, as assessed by cell viability and clonogenic assays and corroborated by Monte Carlo microdosimetry simulations. 相似文献
Bacillus subtilisBsDyP belongs to class I of the dye-decolorizing peroxidase (DyP) family of enzymes and is an interesting biocatalyst due to its high redox potential, broad substrate spectrum and thermostability. This work reports the optimization of BsDyP using directed evolution for improved oxidation of 2,6-dimethoxyphenol, a model lignin-derived phenolic. After three rounds of evolution, one variant was identified displaying 7-fold higher catalytic rates and higher production yields as compared to the wild-type enzyme. The analysis of X-ray structures of the wild type and the evolved variant showed that the heme pocket is delimited by three long conserved loop regions and a small α helix where, incidentally, the mutations were inserted in the course of evolution. One loop in the proximal side of the heme pocket becomes more flexible in the evolved variant and the size of the active site cavity is increased, as well as the width of its mouth, resulting in an enhanced exposure of the heme to solvent. These conformational changes have a positive functional role in facilitating electron transfer from the substrate to the enzyme. However, they concomitantly resulted in decreasing the enzyme’s overall stability by 2 kcal mol−1, indicating a trade-off between functionality and stability. Furthermore, the evolved variant exhibited slightly reduced thermal stability compared to the wild type. The obtained data indicate that understanding the role of loops close to the heme pocket in the catalysis and stability of DyPs is critical for the development of new and more powerful biocatalysts: loops can be modulated for tuning important DyP properties such as activity, specificity and stability. 相似文献