tempo and metaperiodate

Foods rich in cereal β-glucan are efficient dietary tools to help reduce serum cholesterol levels and hence the risk of cardiovascular diseases. However, β-glucan undergoes various reactions during food processing, which alter its viscous properties and interactions with components of the gastrointestinal tract. It has been proposed in the literature that oxidation and partial hydrolysis increase β-glucan's bile acid-binding activity, and therefore its effectiveness in lowering cholesterol. Here, the passage kinetics of a bile salt mix across a dialysis membrane was studied with or without oat and barley β-glucan extracts, native or modified (partial hydrolysis and oxidations by sodium periodate or TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl)). Bile acid-retention turned out to be purely a function of viscosity, with the most viscous native extracts exhibiting the strongest retardation of bile acid permeation. Opposite of what was suggested in the literature, oxidation and molecular weight reduction do not seem to increase the bile acid-binding capability of β-glucan.

Topics: Avena; beta-Glucans; Bile Acids and Salts; Cyclic N-Oxides; Diffusion; Hordeum; Hydrolysis; Kinetics; Oxidation-Reduction; Periodic Acid; Viscosity

TEMPO and periodate are combined in a one-shot reaction to oxidise cellulose and produce nanocellulose gels with a wide range of degree of substitution (DS). Highly-oxidised cellulose nanofibres with a high charge of -80 mV were produced. The strong electrical repulsion between TEMPO-periodate oxidised nanofibres (TPOF) results in the formation of well-separated nanofibres with a diameter of 2-4 nm, albeit depolymerised due to high oxidation. TPOF produces highly-transparent gels due to smaller aspect ratio and high surface charge. These properties induce a reduced viscosity and moduli of the gels by decreasing fibre entanglement. TPOF gels are more stable at basic pH and high ionic strength than TEMPO-oxidised gels due to their higher surface charge. Freeze-dried TPOF gels also exhibit remarkable water holding capacity due to enhanced immobilisation of water molecules. The excellent optical properties of the highly transparent gel for red blood cells analysis open new possibilities in diagnostics application.

Topics: Absorption, Physicochemical; Biocompatible Materials; Cellulose; Cyclic N-Oxides; Erythrocytes; Gels; Humans; Hydrogen-Ion Concentration; Nanofibers; Osmolar Concentration; Oxidation-Reduction; Periodic Acid; Rheology; Surface Properties; Viscosity; Water

Cellulose nanofibril (CNF) materials have been widely studied in recent years and are suggested for a wide range of applications, e.g., medical and hygiene products. One property not very well studied is the interaction between bacteria and these materials and how this can be controlled. The current work studies how bacteria adhere to different CNF materials modified with polyelectrolyte multilayers. The tested materials were TEMPO-oxidized to have different surface charges, periodate-oxidized to vary the water interaction and hot-pressed to alter the surface structure. Then, multilayers were constructed using polyvinylamine (PVAm) and polyacrylic acid. Both the material surface charge and water interaction affect the amount of polymer adsorbed to the surfaces. Increasing the surface charge decreases the adsorption after the first PVAm layer, possibly due to conformational changes. Periodate-oxidized and crosslinked films have low initial polymer adsorptions; the decreased swelling prevents polymer diffusion into the CNF micropore structure. Microscopic analysis after incubating the samples with bacterial suspensions show that only the materials with the lowest surface charge enable bacteria to adhere to the surface because, when adsorbing up to 5 layers PVAm/PAA, the increased anionic surface charge appears to decrease the net surface charge. Both the amounts of PVAm and PAA influence the net surface charge and thus the bacterial adhesion. The structure generated by the hot-pressing of the films also strongly increases the number of bacteria adhering to the surfaces. These results indicate that the bacterial adhesion to CNF materials can be tailored using polyelectrolyte multilayers on different CNF substrates.

Topics: Acrylic Resins; Adsorption; Bacterial Adhesion; Cellulose; Cyclic N-Oxides; Escherichia coli; Nanoparticles; Nitrogen; Oxygen; Periodic Acid; Polyelectrolytes; Polymers; Polyvinyls; Spectroscopy, Fourier Transform Infrared; Surface Properties; Water

The novel catalytic method for the oxidative rearrangement of tertiary allylic alcohols to beta-substituted alpha,beta-unsaturated ketones is described. TEMPO/NaIO4-SiO2 causes facile and efficient oxidative rearrangement of various acyclic substrates as well as medium-sized and macrocyclic substrates.

Topics: Alkylation; Catalysis; Cyclic N-Oxides; Ketones; Molecular Structure; Oxidation-Reduction; Periodic Acid; Propanols; Silicon Dioxide