title: Self-association of mucin.
abstract: Aggregation phenomena in aqueous solutions of purified human tracheobronchial mucin have been studied by rheological methods, steady-state fluorescence, quasielastic light scattering, and spin probe techniques. At temperatures below 30 degrees C and concentrations above 15 mg/mL and in the absence of chaotropic agents, mucin solutions are viscoelastic gels. A gel-sol transition is observed at temperatures above 30 degrees C that is manifested by the diminishing storage modulus and a loss tangent above unity throughout the studied frequency range of the oscillatory shear. No decline in the mucin molecular weight is observed by size-exclusion chromatography above 30 degrees C in the absence of redox agents or proteolytic enzymes. Aggregation of hydrophobic protein segments of the mucin chains at 37 degrees C is indicated by QELS experiments. The decreasing polarity of the microenvironment of pyrene solubilized into mucin solutions at temperatures above 30 degrees C, concomitant with the gel-sol transition, shows the hydrophobicity of the formed aggregates. ESR spectra of the fatty acid spin probe, 16-doxylstearic acid indicate that the aggregate-aqueous interface becomes more developed at elevated temperatures.
authors.affiliation: Department of Physics, Center for Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA. cpbrolev@msn.com
authors.forename: L E
authors.initials: LE
authors.lastname: Bromberg
authors.forename: D P
authors.initials: DP
authors.lastname: Barr
mesh_terms: D001980:Bronchi / Q000737:chemistry*; D002021:Buffers; D002850:Chromatography, Gel; D002851:Chromatography, High Pressure Liquid; D004578:Electron Spin Resonance Spectroscopy; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D007202:Indicators and Reagents; D008027:Light; D009077:Mucins / Q000737:chemistry* / Q000302:isolation & purification; D012212:Rheology; D012542:Scattering, Radiation; D013050:Spectrometry, Fluorescence; D013816:Thermodynamics; D014132:Trachea / Q000737:chemistry*
chemical_list: D002021:Buffers; D007202:Indicators and Reagents; D009077:Mucins