Study of the electrochemical oxidation of reduced nicotinamide adenine dinucleotide.

Electroosmotic properties and peak broadening in field-amplified capillary electrophoresis

Pore size distribution analysis of gel substances by size exclusion chromatography

Apparent pore size distributions of chromatography media

β-Glucans in barley endosperm cell walls exist as polymers of very high molecular weight (about 4 × 107 daltons) containing firmly linked peptide sequences. This peptidic material is an essential part of the structure of the β-glucan complex as it exists in the cell wall. Rupture of peptide bonds by hydrazinolysis or with the proteolytic enzyme thermolysin gives β-glucans similar in size to those from short-grown green malts (about 106 daltons). This suggests that proteolysis is the first step in β-glucan degradation.

Large β-glucans are not all precipitated in 30% (w/v) ammonium sulphate; only 34% of the β-glucan in a hot aqueous extract of cell walls is precipitated. The amount is increased to 63% if the cell walls have been previously dehydrated.

Prolonged incubation of cell wall β-glucan at 40°C, mechanical stress, chromatography lasting 8–10 h at or above 65°C, or chromatography in M sodium chloride causes some disassociation of high molecular weight β-glucan to a size of about 107 daltons. Heating a solution for 1 h at 100°C does not disassociate the β-glucan.

Pentosans isolated from cell walls are not covalently linked to the β-glucans and can be separated from them by molecular sieve chromatography. They have a higher xylose/arabinose ratio than previously reported for barley pentosans. The pentosan molecules extracted by water are smaller (106 daltons) than those extracted by alkali (5 × 106 daltons).

Little difference was observed in the chemical or physical properties of cell wall materials of barley cultivars of different malting qualities.

THE MODE OF BINDING OF β-GLUCANS AND PENTOSANS IN BARLEY ENDOSPERM CELL WALLS

Evaluation of porous silica beads as a new packing material for chromatographic columns. Application in gel permeation chromatography

Evaluation of porous silica beads as packing material for chromatographic columns. Applications in gas-solid chromatography

Spherical porous silica beads, a new material manufactured by Pechiney-Saint-Gobain, has been studied as a packing material for gel permeation chromatography columns. By choosing an appropriate pore size distribution, supports of good selectivity have been obtained. Universal calibration curves have been determined by plotting retention volumes for various polymer standards [polystyrene, poly(vinyl chloride), and dextran] against the logarithm of the product Mw[n]. The nature of the polymer and the solvent (tetrahydrofuran or water) does not appear to affect much the calibration curve for a given support. Column efficiency was evaluated by measuring zone spreading as a function of column length, flow rate, and average particle diameter. The experimental results show that reproducible, uniform, and inherently efficient columns of good selectivity can be prepared with silica beads of average diameter, larger than 100 μ. In view of the observed decrease of efficiency loss at higher flow rates and of the relatively low pressure drop, porous silica beads appear to be a promising packing material for high-speed analytical gel permeation chromatography.

Raymond. Beau

Papers

Evaluation of porous silica beads as a new packing material for chromatographic columns. Application in gel permeation chromatography

Evaluation of porous silica beads as packing material for chromatographic columns. Applications in gas-solid chromatography

Evaluation of analytical gel permeation chromatography columns packed with porous silica beads