RESUMEN
The conformation properties of clinically relevant hybrid macromolecular antioxidants (dextran hydrophobically modified by sterically hindered phenols) in aqueous solution were characterized by a combination of dynamic light scattering (DLS), size exclusion chromatography (SEC), and small-angle neutron scattering (SANS). We were able to split and analyze separately two different types of polydispersity -polydispersity over molecular weights and the one over substitution degree. The properties of the hybrid macromolecules are determined by the number of hydrophobic antioxidants in a single molecule. An insertion of hydrophobic groups into a hydrophilic chain changes the conformation of a single conjugate macromolecule. We have established that with the increasing of a number of hydrophobic antioxidant groups, a conformational transition occurs where a single conjugate undergoes a transition from a Gaussian coil conformation to a more compact structure.
Asunto(s)
Antioxidantes/química , Dextranos/química , Interacciones Hidrofóbicas e Hidrofílicas , Fenoles/química , Conformación de Carbohidratos , Cromatografía en Gel , Hidrodinámica , Luz , Difracción de Neutrones , Dispersión de Radiación , Dispersión del Ángulo Pequeño , ViscosidadRESUMEN
Controlled ion-exclusion allows compensation of hydrophobic adsorption in size-exclusion chromatography of negatively charged methacrylic acid-methyl methacrylate (Eudragit) polymers using methanol as a mobile phase. Properly selected low-ionic-strength conditions below 5 mM LiCl provide correct separation in the size-exclusion mode. Possible disturbing effects, mainly related to light scattering, under low-salt conditions are discussed and shown to be negligible if on-line concentration-light scattering detection is used. The absence of these disturbances is checked by a comparison of experiments performed in methanol containing 1.25 mM and 2.5 mM LiCl. Molecular mass averages and distributions identical within the experimental error are obtained.