P. W. Kent

The effect of ions on the viscometric and ultracentrifugal behaviour of Tamm-Horsfall glycoprotein

Abstract An investigation has been made of the changes in viscosity of solutions of the urinary glycoprotein which occur on addition of sodium, CaCl2 or MgCl2. 1. 1.Glycoprotein solutions of ⩽ 0.15 mg/ml maintained in a low ionic strength Tris HCl buffer, pH 8.0, show an increase in viscosity leading to gel formation at a Ca2+ concentration of 6–7 mM. 2. 2.Such an increase can be brought about by NaCl, but only at concentrations > 60 mM. 3. 3.MgCl2 is slightly less effective than CaCl2 in causing gel formation. 4. 4.When both NaCl and CaCl2 are present the effect on viscosity of the glycoprotein is additive. 5. 5.|Ultracentrifugal analysis demonstrates that gel formation involves production of very rapidly sedimenting material.

Mucus-glycoproteins (mucins) of the cat trachea: characterisation and control of secretion.

Glycoproteins produced by the tracheae of anaesthetized cats were radiolabelled biosynthetically by a pulse administration of Na2 35SO4 and [3H]glucose into the tracheal lumen. Subsequently, radiolabelled secretions were washed from the tracheal lumen. Repeated doses of pilocarpine and then ammonia vapour were given to stimulate secretion. Pilocarpine-stimulated glycoproteins, which came mainly from the submucosal glands, were particularly enriched with 35S. Ammonia-stimulated secretions, which probably came mostly from the microvillous border of the surface epithelium, contained mainly 3H radioactivity but little 35S. Two negatively-charged glycoproteins of different molecular size were identified in the secretions: the larger component was excluded on Sepharose CL-4B and it had a higher 3H 35S ratio than the smaller component which was retarded on Sepharose CL-4B. The relative amount of the smaller component decreased progressively with repeated pilocarpine stimulation and it was not detected in secretions induced by ammonia. Pilocarpine stimulation caused little alteration in carbohydrate composition of the secreted glycoproteins. In response to ammonia, glycoproteins were secreted with a high sialic acid content but quantitatively they represented a small amount of material compared with that induced by pilocarpine. These findings suggest that tracheal glycoproteins from different epithelial-cell sources have distinctive chemical compositions and that their secretions may be independently regulated. The 35S-rich high-molecular-weight glycoproteins from the submucosal glands were of the mucin-type but those derived from the microvillus border may represent a different class of airway glycoproteins from typical epithelial mucins.

The binding of hydrogen and calcium ions by Tamm-Horsfall glycoprotein

Abstract 1. 1. The hydrogen ion titration curves of Tamm-Horsfall urinary glycoprotein in 6 M guanidine · HCl showed that, for every 100 000 g unit, the 16 sialic acid residues revealed by analysis were fully titratable, but only 92 residues of aspartate, glutamate and α-carboxyl groups out of a total of 128 were available to react with H + . 2. 2. The titration curve of this glycoprotein from fibrocystic children was similar. 3. 3. An ultrafiltration technique has been developed to measure Ca 2+ binding directly in the range of Ca 2+ concentration (0.5–9 mM) over which marked increases in viscosity have been observed. 4. 4. Ca 2+ binding at first increased approx. linearly with concentration of free Ca 2+ and revealed a maximum of 0.45 mmole Ca 2+ /g glycoprotein bound at 6 mM of free Ca 2+ , when gel formation occurred. 5. 5. The maximum binding of Ca 2+ corresponds to an approx. 80% neutralisation of the total negative charge determined by titration. 6. 6. The implications of these findings are discussed in relation to the possible physiological relationships between Ca 2+ and the urinary glycoprotein.

The crystal and molecular structure of O-(β-D-xylopyranosyl)-L-serine and its copper (II) complex and some of their reactions

Abstract The interatomic distances and angles have been evaluated in xylosyl serine and its Cu(II) complex by X-ray crystal analysis. Physical data are provided for the acid and alkaline degradation of the former, together with evidence for the catalytic effect on Cu(II) on its alkaline elimination.