The physicochemical characterisation of pepsin degraded pig gastric mucin

Mucins are the main macromolecular components of the mucus secretions that cover the oral cavity, gastrointestinal and urogenital tracts of animals. The properties of the mucus secretions are therefore directly correlated with the physicochemical properties of mucin glycoproteins. In this study, mucins were obtained from pig gastric mucous after digestion with pepsin at 37 ⁰C for 4 hours, these mucins were characterised in terms of compositional and hydrodynamic properties. Compositional analysis showed that this mucin contains protein (15%), carbohydrates (55%) of which the constituents are: fucose (4%), galactose (9%), glucosamine (55%), glucosamine (33%) and sialic acid (2%). The latter component gives the mucin polymer a pH-dependant negative charge, with a -potential of -3 mV at pH 1.2 up to -11 mV at pH 7.4. The weight average molar mass was ~1 x 106 g/mol and intrinsic viscosity was ~0.42 dL/g although there was a small pH dependency due to the polyelectrolyte behaviour of the polymer. The measurements of viscosity versus shear rate showed shear thinning behaviour and the critical overlap concentration was determined to be 10-11% w/v indicating a compact structure. Knowledge of these properties is fundamental to the understanding interactions of mucins, with for example, novel drug delivery systems

Hydrolytic Degradation of Heparin in Acidic Environments:Nuclear Magnetic Resonance Reveals Details of Selective Desulfation

Heparin is a complex glycosaminoglycan, derived mainly from pig mucosa, used therapeutically for its anticoagulant activity. Yet, owing largely to the chain complexity, the progressive effects of environmental conditions on heparin structure have not been fully described. A systematic study of the influence of acidic hydrolysis on heparin chain length and substitution has therefore been conducted. Changes in the sulfation pattern, monitored via 2D NMR, revealed initial de-N-sulfation of the molecule (pH 1/ 40 °C) and unexpectedly identified the secondary sulfate of iduronate as more labile than the 6-O-sulfate of glucosamine residues under these conditions (pH 1/ 60 °C). Additionally, the loss of sulfate groups, rather than depolymerization, accounted for most of the reduction in molecular weight. This provides an alternative route to producing partially 2-O-de-sulfated heparin derivatives that avoids using conventional basic conditions and may be of value in the optimization of processes associated with the production of heparin pharmaceuticals