Terence Painter

Lindow man, tollund man and other peat-bog bodies: The preservative and antimicrobial action of Sphagnan, a reactive glycuronoglycan with tanning and sequestering properties

Abstract The tanning reaction that contributes to the preservation of animal tissues by peat consists of a Maillard reaction between the free amino-groups of collagen and reactive carbonyl groups in a soluble glycuronoglycan (‘sphagnan’) containing residues of d - lyxo -5-hexosulopyranuronic acid. Sphagnan is a complex, pectin-like material which is covalently linked to cellulosic and amyloid-like chains in living Sphagnum moss, but slowly liberated by autohydrolysis into the ambient water as the dead moss is converted into peat. It is a precursor of aquatic humus from Sphagnum peat, and the tanning of adventitious collagen in animal remains is only one manifestation of the continuous incorporation of ammonia, aminoacids and polypeptides from a wide variety of sources into the structure of the humic acid molecule. Sphagnan can also suppress microbial activity by reacting with exo-enzymes and sequestering essential, multivalent metal cations.

Polysaccharides in desert reclamation: Compositions of exocellular proteoglycan complexes produced by filamentous blue-green and unicellular green edaphic algae

Abstract The filamentous blue-green alga Nostoc calcicola Geitler, strain 79WA01, showed a peak production of ∼70% of its biomass as a mixture of exocellular proteoglycan complexes, containing 3–30% of a polypeptide moiety and >70% of a complex glycuronoglycan. The former contained high proportions of Asp, Glu, Arg, and amido-NH 3 , in addition to ∼35% of “hydrophobic” amino-acids. The latter varied in composition in different fractions: GalA (2.5–10.3%), GlcA (4.7–11.5%), Glc (11.7–39.0%), Xyl (5.7–17.9%), Man (2.7–9.5%), Gal (5.7–9.5%), Fuc (1.5–11.1%), Ara (1.9–4.3%), and Rha (1.4–4.4%). None of the fractions showed a stoichiometric ratio of sugar residues. Palmelloid cells of three unicellular green soil-algae of the genus Chlamydomonas yielded ∼70% of their dry weight as capsular mucilage. About 50% of the sodium salt of this material was soluble in water, and contained 3–12% of polypeptide and 88–97% of glycuronoglycan (GlcA:Glc:Xyl = 1:1:3 for C. humicola Lucksch, and GlcA:Gal = 1:2 for C. peterfii Gerloff and C. sajao Lewin). These categorical differences in sugar composition, together with narrow composition distributions, suggested regular structures for the glycuronoglycans. The remainder of the mucilages contained essentially the same glycuronoglycan chains, but a higher proportion of polypeptide. These materials did not form true solutions in water, but dispersed as microgel particles.

Control of depolymerisation during the preparation of reduced dialdehyde cellulose

Abstract The severe depolymerisation that occurs when cellulose is oxidised by periodate can be greatly diminished by carrying out the oxidation in steps, with borohydride reduction after each, and by using propan-1-ol as a radical scavenger in the oxidation steps. The reduction steps greatly increase the rate of Malapradian oxidation by eliminating hemiacetal structures and increasing the solubility of the substrate. They also minimise free-radical-mediated depolymerisation, and prevent the over-oxidation (stepwise peeling) that otherwise ensues at the newly liberated reducing end-groups. The use of regenerated cellulose or mercerised cellulose in order to increase accessibility is also advantageous. Depolymerisation by β-elimination in the reduction steps can be minimised by using very concentrated aqueous sodium borohydride. By these methods, a sample of fully oxidised and reduced cellulose with M n = 132,000 was prepared.

Concerning the wound-healing properties of Sphagnum holocellulose: the Maillard reaction in pharmacology

Sphagnum wound dressings can be 3-4 times as absorbent as cotton equivalents, but they also react chemically with proteins of all kinds. This reactivity gives them the potential of immobilizing whole bacterial cells as well as the enzymes, exotoxins, and lysins secreted by the most invasive pathogens. Once immobilized, enzymes and (by inference) exotoxins and lysins are rapidly inactivated by a Maillard reaction. The complex pectin in Sphagnum is structurally similar to known, immunostimulatory pectins from other plants, including some that are traditionally used for wound healing.

Carbohydrate polymers in desert reclamation: the potential of microalgal biofertilizers

Abstract The use of fast-growing, microscopic soil (edaphic) algae as ‘green manure’ seems to offer the only realistic hope of halting and reversing desert encroachment in the Sahel and other semi-arid regions. The capsular and sheath proteoglycans produced by green and blue-green edaphic algae are of central significance in soil neogenesis. Fundamental studies of their water-retaining and particle-aggregating properties, their ability to release phosphate and trace elements from insoluble minerals, and their ability to store nitrogen and release it slowly under field conditions are essential to the development of biofertilizer technology.

Details of the fine structure of nigeran revealed by the kinetics of its oxidation by periodate

Abstract A theoretical analysis of the kinetics of periodate oxidation of nigeran from Aspergillus niger revealed that, whereas 78% of the 4-linked d -glucopyranosyl residues were present as isolated singlets (with 3-linked residues in both neighbouring positions), the remaining 22% were present as isolated doublets. Sequences of more than two contiguous 4-linked residues were not detected.

Periodate oxidation: a source of error in the assay of formaldehyde with chromotropic acid

Abstract Bisulphite is an unsuitable reagent for removing the excess of periodate from solution prior to the determination of formaldehyde, because the reaction is too slow. Serious errors may arise, but they can be eliminated by using an excess of myo-inositol to reduce the periodate.

PREPARATION AND STRUCTURAL INVESTIGATION OF ASCOPHYLLAN

ABSTRACT Ascophyllan is a polysaccharide extracted together with alginic acid from the brown alga Ascophyllum nodosum (L.) Le Jol. It can be separated from alginic acid by precipitation with acid and from other accompanying polysaccharides by fractional precipitation with salt and alcohol. Prepared by this technique, ascophyllan behaves as a homogeneous material by free-boundary electrophoresis. Paper chromatography of acid hydrolysates demonstrated that ascophyllan is a heteropolysaccharide consisting of fucose, xylose, uronic acid and sulphate half-ester, and analytical data indicate these compounds to be present in approximately equimolecular proportions. A polypeptide material is also attached to the molecule. Partial acid hydrolysis favours the idea of a backbone structure, consisting mainly of uronic acids, to which is attached side chains of a sulphated fuco-xylan. The acid resistant backbone was isolated and demonstrated to be different from ascophyllan itself both analytically and by determination of the electrophoretic mobility as a function of pH. A disaccharide containing fucose and xylose has been isolated, thus providing evidence that ascophyllan is not a mixture of a fucoidan and a xylan. The disaccharide has been tentatively identified as 3- O -xylosyl-fucose.