Galactose-Substituted Alginate 2: Conformational Aspects
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- 作者：Ivan Donati ; Anna Coslovi ; Amelia Gamini ; Gudmund Skjå ; k-Bræ ; k ; Amedeo Vetere ; Cristiana Campa ; and Sergio Paoletti
- 刊名：Biomacromolecules
- 出版年：2004
- 出版时间：January 2004
- 年：2004
- 卷：5
- 期：1
- 页码：186 - 196
- 全文大小：143K
- 年卷期：v.5,no.1(January 2004)
- ISSN：1526-4602
文摘
Galactose moieties have been introduced on the uronic groups of alginates from different sources via anN-glycosidic bond, thus affecting the net charge on the polymer chain. The modified polymers have beenanalyzed by means of viscosity and of high-performance size-exclusion chromatography combined withrefractive index multiple angle laser light scattering (HPSEC-RI-MALLS) measurements. The latter techniqueenabled us to determine the molecular weight of the modified polymers, proving that the synthetic proceduredid not affect the chemical integrity of the chain. The intrinsic viscosity and the radius of gyration datashowed that the hydrodynamic properties of the polymer chain varied with the degree and the pattern ofsubstitution. In the presence of a relatively low galactose content (up to 19%), a decrease of the hydrodynamicdimensions of the coil was experienced, while on increasing the degree of substitution (especially on GGdiads) a re-extension of the chain was discovered. Measurements of intrinsic viscosity at different values ofthe degree of dissociation have demonstrated that this effect cannot be solely explained by the reduction ofthe charge density of the polymer. Rather, it implies the occurrence of conformational changes of the chainthat are specific to the chemical nature of the site of substitution. These data have been supported by thevalues of the persistence length of the natural and modified polymers obtained with the Doty-Benoit equation.The chiro-optical properties of the modified polymers studied by means of circular dichroism (CD)spectroscopy confirmed that conformational variations occurred to the polymeric chain upon introductionof galactose residues.