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Oligomerization of Pharmaceutically Relevant Insulin Analogues for Varying Concentration and Salinity Revealed by Small-Angle X-ray Scattering.

Grethe Vestergaard JensenKatrine R RosenmejerPie HudaLise Arleth
Published in: Molecular pharmaceutics (2021)
Two different insulin analogues, insulin degludec and lithocholyl insulin, were studied by small-angle X-ray scattering with respect to their self-assembly and interactions in solution at different concentrations of insulin and salt, NaCl. Very different behavior was observed for the two. Insulin degludec, linked to a hexadecanedioic acid, consistently formed di-hexamers, without any further oligomeric growth upon screening of electrostatic repulsions, indicating a stable di-hexamer unit without further oligomerization, as expected in the presence of phenol. The other insulin analogue, linked to the sterol lithocholic acid, formed n-hexamers with n ranging from 1 to 15, increasing with NaCl concentration and insulin concentration, indicating attractive forces in competition with the electrostatic repulsion and solution entropy. At the highest concentration of insulin and NaCl, a liquid crystal phase was observed, which has not previously been identified, featuring a quadratic structure organized into layers, which might hold interesting properties for pharmaceutical applications.
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