Understanding the stability of zeolitic imidazolate framework-8 (ZIF-8) under physiological conditions is critical in biotechnology and biomedicine for biosensing, biocatalysis, and drug delivery. The use of ZIF-8 has shown that this metal organic framework (MOF) and its derived bio-composites can degrade in presence of buffer solutions. Here we present an in-depth analysis of the structural and chemical changes of pure ZIF-8 particles exposed to phosphate buffered saline (PBS) media. Two different particle sizes (2 μm and 250 nm) were selected and the decomposition operated by 10 mM PBS (aka 1X) was studied using powder X-ray diffraction (PXRD), Fourier transformed infrared spectroscopy (FTIR), time resolved atomic force microscopy (AFM), in situ small angle X-ray scattering (SAXS), and ³¹P NMR.

In the yeast Saccharomyces cerevisiae, two acyl‐CoA:sterol acyltransferases (ASATs) that catalyze the synthesis of steryl esters have been identified, namely Are2p (Sat1p) and Are1p (Sat2p). Deletion of either ARE1 or ARE2 has no effect on cell viability, and are1are2 double mutants grow in a similar manner to wild‐type despite the complete lack of cellular ASAT activity and steryl ester formation [Yang, H., Bard, M., Bruner, D. A., Gleeson, A., Deckelbaum, R. J., Aljinovic, G., Pohl, T. M., Rothstein, R. & Sturley, S. L. (1996) Science272, 1353–1356; Yu, C., Kennedy, J., Chang, C. C. Y. & Rothblatt, J. A. (1996) J. Biol. Chem.271, 24157–24163]. Here we show that both Are2p and Are1p reside in the endoplasmic reticulum as demonstrated by measuring ASAT activity in subcellular fractions of are1 and are2 deletion strains. This localization was confirmed by fluorescence microscopy using hybrid proteins of Are2p and Are1p fused to green fluorescent protein (GFP). Lipid analysis of are1 and are2 deletion strains revealed that Are2p and Are1p utilize sterol substrates in vivo with different efficiency; Are2p has a significant preference for ergosterol as a substrate, whereas Are1p esterifies sterol precursors, mainly lanosterol, as well as ergosterol. The specificity towards fatty acids is similar for both isoenzymes. The lack of steryl esters in are1are2 mutant cells is largely compensated by an increased level of free sterols. Nevertheless, terbinafine, an inhibitor of ergosterol biosynthesis, inhibits growth of are1are2 cells more efficiently than growth of wild‐type. In a growth competition experiment are1are2 cells grow more slowly than wild‐type after several rounds of cultivation, suggesting that Are1p and Are2p or steryl esters, the product formed by these two enzymes, are more important in the natural environment than under laboratory conditions.

The two most prominent neutral lipids of the yeast Saccharomyces cerevisiae, triacylglycerols (TAG) and steryl esters (SE), are synthesized by the two TAG synthases Dga1p and Lro1p and the two SE synthases Are1p and Are2p. In this study, we made use of a set of triple mutants with only one of these acyltransferases active to elucidate the contribution of each single enzyme to lipid particle (LP)/droplet formation. Depending on the remaining acyltransferases, LP from triple mutants contained only TAG or SE, respectively, with specific patterns of fatty acids and sterols. Biophysical investigations, however, revealed that individual neutral lipids strongly affected the internal structure of LP. SE form several ordered shells below the surface phospholipid monolayer of LP, whereas TAG are more or less randomly packed in the center of the LP. We propose that this structural arrangement of neutral lipids in LP may be important for their physiological role especially with respect to mobilization of TAG and SE reserves.

Paper-based food packaging materials are widely used, renewable, and biodegradable. Because of its porous structure, paper has poor or no barrier performance against grease, water vapor, water, and volatile organic compounds. Moreover, recycled paperboard can be a source of organic residuals that are able to migrate into packed food. Two different types of paperboard produced from primary and secondary cellulosic fibers were coated using renewable materials, such as alginate and chitosan, and comprehensive barrier measurements showed multifunctional barrier properties of these two biomaterials. Both paper substrates were successfully coated using a draw-down coater, and the measured air permeability of the coated samples was 0 mL·min⁻¹. Grease resistance was improved, while it was possible to reduce water vapor transmission, the migration of mineral oil saturated hydrocarbons and mineral oil aromatic hydrocarbons (MOSH/MOAH), and the permeation of volatile compounds for both paper substrates when compared with uncoated substrates. Wettability and water absorptiveness of chitosan- and alginate-coated papers were found to be substrate-dependent properties, and could be significantly affected by bio-based coatings. In summary, industrially produced paperboard was upgraded by coating it with the naturally biodegradable biopolymers, alginate and chitosan, thus achieving extraordinary barrier performance for various applications within the packaging industry.