Effects of elevated nitrogen fertilizer on the multi-level structure and thermal properties of rice starch granules and their relationship with chalkiness traits.

BACKGROUND: Chalkiness in rice reduces its market value and affects consumer acceptance. Research on the mechanism of chalkiness formation has focused primarily on the activity of key enzymes of carbon metabolism and starch accumulation. The relationship between the formation of chalkiness induced by N fertilizer and rice starch's multi-level structure and thermal properties still needs to be fully elucidated. RESULTS: In this study, the rates of chalky grains and degree of chalkiness decreased with the increase in N fertilizer dosage. This was attributed to an increased proportion of short chains, ordered structure carbon chains, small starch granules, and branched starches, and a higher degree of crystallinity and ΔHg in protein, and a decreased proportion of amylose, large starch granules, and weighted average diameter of starch granule surface area and volume. Application of N fertilizer promoted an increased proportion of short-branched chain amylopectin to develop a more ordered carbohydrate structure and crystalline lamella. These effects enhanced the normal development and compactness of starch granules in grains, and improved their arrangement morphology, thereby reducing the chalkiness in rice. CONCLUSION: These changes in starch multi-level structure and protein improve the physicochemical characteristics of starch and enhance the fullness, crystallinity and compactness of starch granules, while synergistically increasing the regularity and homogeneity of starch granules and thus optimizing the stacking pattern of starch granules, leading to a reduction in rice chalkiness under nitrogen fertilization and thus improving the appearance of rice. © 2023 Society of Chemical Industry.

Comparative yields of antimicrobial peptides released from human and cow milk proteins under infant digestion conditions predicted by in silico methodology.

Mammalian milk proteins are known to encrypt antimicrobial peptides (AMPs) which can be passively released and exert bioactivity in the gastrointestinal and cardiovascular systems pre- or post-absorption, respectively. However, the contribution of 'passive' food-derived AMPs to the pool of endogenous and microbial AMPs has not been differentiated in previous research. Insight into the consequences of protein digestion and peptide bioactivity can be gained using in silico tools. The aim of this investigation was to use in silico methods to characterise the yields of AMPs released from major proteins in human and cow milk under infant digestion conditions, as relevant to early nutrition. The profiles of major proteins in human and cow milk from UniProtKB/Swiss-Prot, were subjected to in silico digestion by ExPASy-PeptideCutter, and the AMP activity of resulting peptides (≥4 amino acids, AAs) evaluated with the CAMPR3-RF predictive tool. The mass yields and counts of absorbing (≤10 AAs) and non-absorbing (>10 AAs) AMPs, as found in human, cow and 'humanised' ratios of cow milk proteins, were quantified. The results indicated that major whey proteins from both human and cow milks displayed a higher degree of hydrolysis than caseins, consistent with their known 'fast' digestion properties. Larger albumin and lactoferrin proteins generated relatively more and/or longer peptides. Yields of AMPs from cow milk were higher than from human milk, even after standardising the ratio of whey to casein and total protein concentration, as practiced in formulations manufactured for human newborn babies. Whereas alpha-lactalbumin (2.65 g L-1) and lactoferrin (1.75 g L-1) provided the major yields of AMPs in human milk whey proteins; beta-lactoglobulin, which is unique to cow milk, released the highest yield of AMPs in cow milk (3.25 g L-1 or 19.9% w/w of total whey protein), which may represent an important and overlooked biological function of this protein in cow milk.

The role of microbial infection in the pathogenesis of Alzheimer's disease and the opportunity for protection by anti-microbial peptides.

Alzheimer's disease (AD) is the most common cause of dementia. Its pathology is primarily characterized by extracellular deposits of amyloid ß peptide and intracellular neurofibrillary tangles. Current rationales to explain the pathogenesis of AD include amyloid cascade, inflammation, infection defense and anti-microbial protection hypotheses. This review focuses on recent advances in the infection hypothesis, in particular on those pathogenic microbes that act systemically, via periodontal and gastro-intestinal infection routes. It is proposed that the evidence convincingly supports that pathogenic microbial infection is associated with, and is likely a causative trigger for, AD pathology. Microbes can drive AD pathology by two main pathways: either by directly infecting the brain and stimulating amyloid-mediated defence (causative trigger) or indirectly, by stimulating the pro-inflammatory effects of infection. In this context, it follows that anti-microbial/anti-infection therapies could be effective for regulating the pathology and symptoms of AD, depending on the stage of disease. As long-term administration of traditional antibiotic therapy is not recommended, alternative antibiotic agents such as anti-microbial peptides (AMPs), could be preferred for intervention and disease management of AD.

Synthesis of Ultrahigh Molecular Weight PLAs Using a Phenoxy-Imine Al(III) Complex.

l- and d-lactide polymerization kinetics using phenoxy-imine ligands of the type Me2Al[O-2-tert-Bu-6-(C6F5N=CH)C6H3] in the presence of n-butanol and benzyl alcohol by ring-opening polymerization into polylactide are investigated. Effects of initiator concentration, catalyst concentration, polymerization temperature, and time on the molecular weight of poly-l-lactide are also investigated. Purification and drying of l-lactide are found to significantly influence the polymerization kinetics and the final molecular weight achieved. Ultrahigh molecular weight poly(l-lactic acid) PLLA (M w = 1.4 × 106 g/mol with D = 1.8) and ultrahigh molecular weight poly(d-lactic acid) PDLA (M w = 1.3 × 106 g/mol with D = 2.0) are obtained when polymerization is performed with a molar ratio of monomer to catalyst (LA/Al) of 8000 for 72 h at 120 °C in the presence of benzyl alcohol with conversions of 96 and 91%, respectively. We report for the first time the synthesis of ultrahigh molecular weight poly-l- and d-lactide using the Me2Al[O-2-tert-Bu-6-(C6F5N=CH)C6H3] catalyst. The identified catalyst is found to be suitable for the synthesis of a broad range of molecular weights.