Controlling the self-assembly of cationic bolaamphiphiles: hydrotropic counteranions determine aggregated structures

The size and substitution pattern of hydrotropic counteranions determine the aggregated structures of cationic bolaamphiphiles.

Importance of thiol-functionalized molecules for the structure and properties of compression-molded glassy wheat gluten bioplastics

High-temperature compression molding of wheat gluten at low water levels yields a rigid plastic-like material. We performed a systematic study to determine the effect of additives with multiple thiol (SH) groups on gluten network formation during processing and investigate the impact of the resulting gluten network on the mechanical properties of the glassy end product. To this end, a fraction of the hydroxyl groups of different polyols was converted into SH functionalities by esterifying with 3-mercaptopropionic acid (MPA). The monofunctional additive MPA was evaluated as well. During low-temperature mixing SH-containing additives decreased the gluten molecular weight, whereas protein cross-linking occurred during high-temperature compression molding. The extent of both processes depended on the molecular architecture of the additives and their concentration. After molding, the material strength and failure strain increased without affecting the modulus, provided the additive concentration was low. The strength decreased again at too high concentrations for polyols with low SH functionalization. Attributing these effects solely to the interplay of plasticization and the SH-facilitated introduction of cross-links is inadequate, since an improvement in both strength and failure strain was also observed in the presence of high levels of MPA. It is hypothesized that, regardless of the molecular structure of the additive, the presence of SH-containing groups induces conformational changes which contribute to the mechanical properties of glassy gluten materials.

Impact of acid and alkaline pretreatments on the molecular network of wheat gluten and on the mechanical properties of compression-molded glassy wheat gluten bioplastics

Wheat gluten can be converted into rigid biobased materials by high-temperature compression molding at low moisture contents. During molding, a cross-linked protein network is formed. This study investigated the effect of mixing gluten with acid/alkali in 70% ethanol at ambient temperature for 16 h followed by ethanol removal, freeze-drying, and compression molding at 130 and 150 °C on network formation and on types of cross-links formed. Alkaline pretreatment (0-100 mmol/L sodium hydroxide or 25 mmol/L potassium hydroxide) strongly affected gluten cross-linking, whereas acid pretreatment (0-25 mmol/L sulfuric acid or 25 mmol/L hydrochloric acid) had limited effect on the gluten network. Molded alkaline-treated gluten showed enhanced cross-linking but also degradation when treated with high alkali concentrations, whereas acid treatment reduced gluten cross-linking. β-Elimination of cystine and lanthionine formation occurred more pronouncedly at higher alkali concentrations. In contrast, formation of disulfide and nondisulfide cross-links during molding was hindered in acid-pretreated gluten. Bioplastic strength was higher for alkali than for acid-pretreated samples, whereas the flexural modulus was only slightly affected by either alkaline or acid pretreatment. Apparently, the ratio of disulfide to nondisulfide cross-links did not affect the mechanical properties of rigid gluten materials.

Bone Dysplasia as a Key Feature in Three Patients with a Novel Congenital Disorder of Glycosylation (CDG) Type II Due to a Deep Intronic Splice Mutation in TMEM165

Three patients belonging to two families presented with a psychomotor-dysmorphism syndrome including postnatal growth deficiency and major spondylo-, epi-, and metaphyseal skeletal involvement. Other features were muscular hypotrophy, fat excess, partial growth hormone deficiency, and, in two of the three patients, episodes of unexplained fever. Additional investigations showed mild to moderate increases of serum transaminases (particularly of aspartate transaminase (AST)), creatine kinase (CK), and lactate dehydrogenase (LDH), as well as decreased coagulation factors VIII, IX, XI, and protein C. Diagnostic work-up revealed a type 2 serum transferrin isoelectrofocusing (IEF) pattern and a cathodal shift on apolipoprotein C-III IEF pointing to a combined N- and O-glycosylation defect. Known glycosylation disorders with similar N-glycan structures lacking galactose and sialic acid were excluded. Through a combination of homozygosity mapping and expression profiling, a deep intronic homozygous mutation (c.792 + 182G>A) was found in TMEM165 (TPARL) in the three patients. TMEM165 is a gene of unknown function, possibly involved in Golgi proton/calcium transport. Here we present a detailed clinical description of the three patients with this mutation. The TMEM165 deficiency represents a novel type of CDG (TMEM165-CDG). This disorder enlarges the group of CDG caused by deficiencies in proteins that are not specifically involved in glycosylation but that have functions in the organization and homeostasis of the intracellular compartments and the secretory pathway, like COG-CDG and ATP6V0A2-CDG.

Fully-branched hyperbranched polymers with a diselenide core as glutathione peroxidase mimics

A novel glutathione peroxidase (GPx) mimic has been prepared by incorporation of a selenium-based catalytic unit into the focal point of a fully-branched hyperbranched polymer. First, an AB(2) monomer consisting of isatin and an electron rich aromatic moiety was polycondensed in the presence of 5-nitroisatin as a core reagent, resulting in a polymer with 100% degree of branching. The latter was coupled to the catalytically active moiety, Br(CH(2))(5) SeSe(CH(2))(5) Br, by nucleophilic substitution of the bromides by the residual amide groups of the incorporated nitroisatin core. The obtained polymer has demonstrated prominent GPx activity as desired, which could be attributed to the hydrophobic, densely branched and core-shell structure of the polymer surrounding the catalytic center.

Bolaamphiphiles bearing bipyridine as mesogenic core: rational exploitation of molecular architectures for controlled self-assembly

A bolaamphiphile (5,5-B2NBr8) bearing a functional bipyridine moiety as the mesogenic core is reported for the first time. 5,5-B2NBr8 was found to self-assemble into uniform fibrous structure in aqueous solution, when the concentration was higher than cmc. Analogues of 5,5-B2NBr8 with structural differences in chain length, headgroup, mesogenic core, and substituted position were synthesized, elucidating that small variances of the molecular structure could lead to dramatic changes of the resulting assemblies. For example, compound 4,4-B2NBr8 showed only spherical colloidal aggregates rather than fibers as 5,5-B2NBr8 did, while the only difference between them was the position at which the alkyl chains were attached onto bipyridine. A probable model for the fibrous structure of 5,5-B2NBr8 was proposed. Moreover, exploiting the coordination capacity of bipyridine, assembly and disassembly of 5,5-B2NBr8 could be reversibly controlled through the addition of EDTA and Cu(II), respectively.

UV-responsive polymeric superamphiphile based on a complex of malachite green derivative and a double hydrophilic block copolymer

We have prepared a UV-responsive polymeric superamphiphile, formed by a malachite green derivative and the double hydrophilic block copolymer methoxy-poly(ethylene glycol)(114)-block-poly(l-lysine hydrochloride)(200) (PEG-b-PLKC) on the basis of electrostatic interactions. The malachite green derivative undergoes photo-ionization upon UV irradiation, which makes it more hydrophilic, resulting in changes in the self-assembly behavior of the polymeric superamphiphile. For this reason, the polymeric superamphiphile originally self-assembles to form sheetlike aggregates, which disassemble after UV irradiation because of the increased solubility of the malachite green derivative. By use of Nile red as a probe, the polarity of the polymeric superamphiphile solution is confirmed to be increased after UV irradiation by fluorescence spectra, which also explains the disassembly of the polymeric superamphiphile.