Equilibrium swelling of pigment gallstones: Evidence for network polymer structure
✍ Scribed by Brian E. Black; Stephen H. Carr; Hideki Ohkubo; J. Donald Ostrow
- Publisher
- Wiley (John Wiley & Sons)
- Year
- 1982
- Tongue
- English
- Weight
- 522 KB
- Volume
- 21
- Category
- Article
- ISSN
- 0006-3525
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✦ Synopsis
Abstract
A major component of pigment gallstones (PS) is a black, insoluble substance. It has been suggested that this pigment material might be a highly crosslinked polymer, and if such were the case, it should imbibe solvent (swell) to the maximum permitted by the crosslinks of its macromolecular network. We measured the equilibrium amount, q~eq~, by which pulverized, desiccated PS swells in different liquids, including isotonic aqueous buffers at pH values from 1.5–11.5. For ionic strengths ≥ 0.15, the dependence of q~eq~ on pH exhibits a broad titration curve with a midpoint near pH 7. q~eq~ was < 1.2 in methanol, dimethylformamide, dimethylsulfoxide, and chloroform. The ir absorbance from vinyl groups in the black pigment was only one‐eighth that of unconjugated bilirubin, the primary chemical building block of PS; this implicates vinyl groups in the formation of a polymer network. The rise in q~eq~ with increasing pH suggests that the carboxyl groups are free to ionize and are therefore not involved in the covalent bonds that make the crosslinked polymer. A network polymer structure would account for the inability to dissolve PS in those solvents in which unconjugated bilirubin is soluble.