Molecular Structure and Rheological Properties of Short-Side-Chain Heavily Glycosylated Porcine Stomach Mucin

Abstract

The current accepted model for high-molecular-weight gastric mucins of the MUC family is that they adopt a polydisperse coil conformation in bulk solutions. We develop this model using well-characterized highly purified porcine gastric mucin Orthana that is genetically close to the human MUC6 type. It has short side chains and low levels of sialic acid residues and includes minute amounts of cysteine residues that, if abundant, can be responsible for the self-polymerization of mucin. We have established that the mucin structure in bulk solutions corresponds to a daisy-chain random coil. Dynamic light scattering experiments probe the internal dynamics of globular subunits (individual daisies) at the approximately 9 nm length scale, whereas viscosity and light scattering measurements indicate that the size of the whole mucin chains is much larger, approximately 50 nm. The bulk viscosity (eta) scales with mucin concentration (c) in a manner similar to that found for short-side-chain synthetic comb polyelectrolytes and is characterized by a transition between semidilute (eta approximately c1/2) and entangled (eta approximately c3/2) regimes.

Surface rearrangement of adsorbed EGCG–mucin complexes on hydrophilic surfaces

“…The measured hydrodynamic radius for pure mucin and EGCG-mucin mixtures at EGCG concentrations < 0.05% w/w ( Figure 3B) is in agreement with previous reports that attribute it to the dynamics of a mucin molecule in a dumbbell conformation [29]. With increasing EGCG concentration, a more complex profile of DLS relaxation time emerges that can be interpreted as a bimodal distribution, where the fast mode corresponds to the dynamics of non-aggregated mucin molecules, while the slow mode is associated with the formation of aggregates.…”

“…Pharmaceutical grade porcine gastric mucin with a molecular weight of 546 kDa [29,30] was purchased from A/S Orthana Kemisk Fabrik (Kastrup, Denmark), extensively dialysed to remove all low molecular weight additives, including salts, and then lyophilized for storage. The refractive index increment  at 633 nm in pure water at 25 •C was determined using a Rudolph J357 refractometer as 0.140 ± 0.002 cm 3 /g, in agreement with previous results [31].…”

Structural hysteresis and hierarchy in adsorbed glycoproteins

“…29 The thickness associated with the native, entangled molecules ͑crosses on Fig. 2͒ lies within this value.…”

Structural and Mechanical Properties of Thin Films of Bovine Submaxillary Mucin versus Porcine Gastric Mucin on a Hydrophobic Surface in Aqueous Solutions

“…31 For this reason, while mucins are often depicted as highly coiled polymer chains in literature, 32,33 the mucins in this study are better described as "dumbbell"-like shape in their conformations. 13,14,34 For instance, a recent small angle x-ray scattering study has revealed that highly purified "Orthana" PGM displays double-globular comb structure with two globules of an average radius of 10 nm connected with the intramolecular chain of ca. 48 nm.…”

“…[37][38][39][40][41]42 Another study on the compositional analysis of "Orthana" PGM indicated the complete absence of charged glycans. 34 The manufacturer's estimation on the amounts of bound sialic acids is also substantially higher for BSM (ca. 9-17%) than PGM (0.5-1.5%) of the total mucin masses.…”