Fabrication of a ternary biocomposite film based on polyvinyl alcohol, cellulose nanocrystals, and silver nanoparticles for food packaging.

Silver nanoparticles (AgNPs) were loaded on deprotonated cellulose nanocrystals (CNCd) and incorporated into polyvinyl alcohol (PVA) to develop novel active food packaging films. The AgNPs were fabricated using the liquid phase chemical reduction method using the sodium borohydride reductant of AgNO3. The analysis using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Thermogravimetric analysis (TGA), Differential scanning calorimetry (DSC), and Ultraviolet-visible spectroscopy (UV-Vis) showed that the CNCd surface had a homogeneous distribution of AgNPs with a diameter of about 100 nm. Additionally, CNCd/Ag was successfully incorporated into the PVA film. The developed PVA/CNCd/Ag film showed significantly improved mechanical properties, thermal stability, and UV barrier properties compared to a neat PVA film. The PVA/CNCd/Ag composite film could significantly preserve bananas for 14 days, preventing deterioration and allowing extended storage periods. This composite film generally shows promise in food packaging and prolongs food's shelf life.

APEX Proximity Labeling as a Versatile Tool for Biological Research.

Most proteins are specifically localized in membrane-encapsulated organelles or non-membrane-bound compartments. The subcellular localization of proteins facilitates their functions and integration into functional networks; therefore, protein localization is tightly regulated in diverse biological contexts. However, protein localization has been mainly analyzed through immunohistochemistry or the fractionation of subcellular compartments, each of which has major drawbacks. Immunohistochemistry can examine only a handful of proteins at a time, and fractionation inevitably relies on the lysis of cells, which disrupts native cellular conditions. Recently, an engineered ascorbate peroxidase (APEX)-based proximity labeling technique combined with mass spectrometry was developed, which allows for temporally and spatially resolved proteomic mapping. In the presence of H2O2, engineered APEX oxidizes biotin-phenols into biotin-phenoxyl radicals, and these short-lived radicals biotinylate electron-rich amino acids within a radius of several nanometers. Biotinylated proteins are subsequently enriched by streptavidin and identified by mass spectrometry. This permits the sensitive and efficient labeling of proximal proteins around locally expressed APEX. Through the targeted expression of APEX in the subcellular region of interest, proteomic profiling of submitochondrial spaces, the outer mitochondrial membrane, the endoplasmic reticulum (ER)-mitochondrial contact, and the ER membrane has been performed. Furthermore, this method has been modified to define interaction networks in the vicinity of target proteins and has also been applied to analyze the spatial transcriptome. In this Perspective, we provide an outline of this newly developed technique and discuss its potential applications to address diverse biological questions.

In-depth study of lin-28 suggests selectively conserved let-7 independent mechanism in Drosophila.

Lin-28 is a conserved RNA-binding protein that is involved in a wide range of developmental processes and pathogenesis. At the molecular level, Lin-28 blocks the maturation of let-7 and regulates translation of certain mRNA targets. In Drosophila, Lin-28 is reported to play a role in oogenesis, muscle formation, and the symmetric division of adult intestinal stem cells. In this study, we characterized Drosophila Lin-28 through a detailed examination of its temporal and spatial expression. Lin-28 is specifically expressed in embryonic nervous and cardiac systems. However, loss or gain of lin-28 function does not cause any abnormality during embryonic development. Instead, the ubiquitous overexpression of Lin-28 leads to lethality from late larval stage to pupal stage, and eye-specific overexpression causes severe cell loss. The ectopic expression of human Lin28A has the same effect as Drosophila Lin-28, indicating functional conservation in Lin-28 orthologs. We also examined the effect of Lin-28 on let-7 biogenesis through the mutant and overexpression analysis. Lin-28 does not block the production of let-7 in Drosophila, which suggests the let-7 independent pathway as a molecular mechanism of Lin-28.