We report on a method for preparation of well-defined synthetic polypeptides by ring-opening polymerization of α-amino acid N-carboxyanhydrides (NCA) initiated by a hydroxyl group. To overcome the issue of slow initiation by hydroxyl group, an acid catalyst was used in initiation step to catalyze opening of the NCA ring by the hydroxyl group and to simultaneously suppress further chain propagation by protonation of the formed amine group. In this way, we have separated slow initiation from the fast chain propagation, since such a combination leads to poorly defined products, and instead performed them in a successive manner. Only after completion of the initiation, the propagation was started by the addition of a base to deprotonate the ammonium group. This method was successfully applied for the synthesis of homopolypeptides by using alcohol as an initiator as well as polypeptide-based block copolymers by using poly(ethylene glycol) or poly(styrene) macroinitiator terminated with the hydroxyl group. This approach not only expands the pool of possible initiators, but also significantly facilities the preparation of polypeptide-based hybrid polymers.
COBISS.SI-ID: 6168602
MOF@polyHIPE hybrid foams were prepared using a metal salt-free technique, wherein metal–organic frameworks were in situ generated from the CuO and ZnO nanoparticles through secondary recrystallization. The MOF phase within the hybrid polyHIPEs as disclosed herein, exhibited superior micropore accessibility and structure hydrostability. These results were the follow up work on the previously reported MOF@polyHIPE hybrid foams (Macromolecular Rapid Communications, 2015, 36, 1605-1611), where we had a micropore clogging and MOF stability issues. In the present work MOFs were not incorporated directly into the emulsion, therefore they were not exposed to water and other emulsion components that affect emulsion stability. The nanoparticle-to-MOF transformation has proven to be an effective technique for preparing MOF@polyHIPE hybrid materials with a high MOF stability and content.
COBISS.SI-ID: 6072090
Asymmetrical flow field-flow fractionation (AF4) technique coupled to a multi-angle light-scattering (MALS) detector with embedded dynamic light-scattering (DLS) module was introduced to study the size-characteristics and shape of soft parti-cles of various size and type; polystyrene nanosphere size standards, lipid droplets (LD), and large unilamellar vesicles (LUV). A range of passage flow velocities at the detector coupled to AF4 at which accurate hydrodynamic size can be extracted from the DLS in flow mode was studied since the particles subjected to a longitudinal flow exhibit not only the Brownian motion due to diffusion, but also the translational movement. In addition, the impact of the rate of the passage flow at the detector in AF4 system on the shape of the artificial LUV of two different sizes and two different compositions was studied by MALS. For comparison, the conventional batch DLS and static light-scattering (SLS) experiments without prior sample separation by size were performed. From a combination of batch and flow light-scattering results we concluded that the passage flow velocities at the detector used in this study; 0.2, 0.5, and 1 mL/min, have no significant impact on the shape of spherical vesicles, however, the flow DLS experiments give accurate hydrodynamic radius (Rh) only at the lowest investigated rate of passage flow at the detector of 0.2 mL/min. With increasing rate of passage flow at the DLS detector, the error in the accuracy of the Rh determination rapidly increases. The error in Rh depends solely on the particle size regardless of the soft particle type.
COBISS.SI-ID: 6240794
We prepared eco-friendly “green” nano composite films, which can be used as a swap for packaging applications. Nanocomposites of starch/cellulose nanofibers, fabricated from pineapple leaf, were prepared by solution mixing followed by casting. The chain confinement was associated with the immobilization of the starch macromolecular chains in the network formed by the nano-scale cellulose fibers as a result of hydrogen bonding interactions. From the results, it was assumed that the starch / glycerol system exhibits a heterogenous nature and cellulose nanofibers tend to move towards the glycerol rich starch phase.The kinetics of diffusion was investigated and typical kinetic parameters were determined and found that the nanocomposites follow pseudo Fickian behaviour.
COBISS.SI-ID: 6139418
Necrosis and ethylene-inducing peptide 1–like (NLP) proteins constitute a superfamily of proteins produced by plant pathogenic bacteria, fungi, and oomycetes. Many NLPs are cytotoxins that facilitate microbial infection of eudicot, but not of monocot plants. Here, we report glycosylinositol phosphorylceramide (GIPC) sphingolipids as NLP toxin receptors. Plant mutants with altered GIPC composition were more resistant to NLP toxins. Binding studies and x-ray crystallography showed that NLPs form complexes with terminal monomeric hexose moieties of GIPCs that result in conformational changes within the toxin. Insensitivity to NLP cytolysins of monocot plants may be explained by the length of the GIPC head group and the architecture of the NLP sugar-binding site. We unveil early steps in NLP cytolysin action that determine plant clade-specific toxin selectivity.
COBISS.SI-ID: 6289178