title: Comparative study of small linear and branched alpha-glucans using size exclusion chromatography and static and dynamic light scattering.
abstract: A series of synthesized small linear and branched alpha-glucans has been studied by dynamic light scattering and combined size exclusion chromatography, refractive index measurement and static light scattering. The alpha-glucan molecules studied were maltose, maltotriose, maltopentaose, maltohexaose, maltoheptaose, panose, 6'-alpha-maltosyl-maltotriose, methyl 6'-alpha-maltosyl-maltotrioside, 6' '-alpha-maltosyl-maltotetraose, 6' ''-alpha-maltotriosyl-maltohexaose, and 6,6' '' '-bis(alpha-maltosyl)-maltohexaose. The alpha-glucan oligosaccharides appeared to be very flexible molecules having a variety of conformations and self-associating into noncovalent dimers and trimers (referring to the single molecule). The size distributions were narrow (compared to pullulan) indicating that the alpha-glucan oligosaccharides are relatively compact molecules. The branched oligomers that include one or more flexible alpha-(1 --> 6) linkages exhibit size distributions corresponding to more compact conformations than their linear counterparts. This observation may be explained by intermolecular interactions or water bridges facilitated by the additional flexibility of these molecules. For the branched maltohexaose, a significant noncovalent trimer formation was observed, whereas in all other cases, noncovalent dimers were formed. Model calculations suggest that both the linear and branched oligomers containing 5-10 alpha-glucose units exist predominantly in a partial or full single turn helix in agreement with the glycosidic linkage preferences derived for these molecules.
authors.affiliation: Plant Biochemistry Laboratory, Department of Plant Biology and Center for Molecular Plant Physiology (PlaCe), The Royal Veterinary and Agricultural University, DK-1871 Frederiksberg C, Denmark.
authors.forename: Mohammed Saddik
authors.initials: MS
authors.lastname: Motawia
authors.forename: Iben
authors.initials: I
authors.lastname: Damager
authors.forename: Carl Erik
authors.initials: CE
authors.lastname: Olsen
authors.forename: Birger Lindberg
authors.initials: BL
authors.lastname: Møller
authors.forename: Søren Balling
authors.initials: SB
authors.lastname: Engelsen
authors.forename: Steen
authors.initials: S
authors.lastname: Hansen
authors.forename: Lars Holm
authors.initials: LH
authors.lastname: Øgendal
authors.forename: Rogert
authors.initials: R
authors.lastname: Bauer
mesh_terms: D002236:Carbohydrate Conformation; D002240:Carbohydrate Sequence; D002850:Chromatography, Gel / Q000379:methods*; D005936:Glucans / Q000737:chemistry*; D008027:Light; D008969:Molecular Sequence Data; D012542:Scattering, Radiation; D013997:Time Factors
chemical_list: D005936:Glucans