Hydration of the amylopectin branch point. Evidence of restricted conformational diversity of the alpha-(1-->6) linkage.
The hydration behavior of a model compound for the amylopectin branch point, methyl 6'-alpha-maltosyl-alpha-maltotrioside, was investigated by combining molecular dynamics simulations in explicit water, 500 MHz NMR spectroscopy, including pulsed field gradient diffusion measurements, and exploratory multivariate data analysis. In comparison with results on a tetrasaccharide analogue, the study reveals that the conformational diversity of the three-bond alpha-(1-->6) linkage becomes quite limited in aqueous solution upon the addition of a fifth glucose residue that elongates the alpha-(1-->6) branch. This investigation reveals two plausible starch branch point structures, one that permits the formation of double helices and one that is adapted for interconnection of double helices. The apparent rigidity of the former is explained by the presence of water pockets/bridges in the vicinity of the branch point that lock the pentasaccharide structure into one conformational family that is able to accommodate the creation of the double-helical amylopectin structure.
Contribution from the Centre for Advanced Food Studies (LMC), The Royal Veterinary and Agricultural University (KVL), Rolighedsvej 30, DK-1958 Frederiksberg C, Denmark.
Francisco
F
Corzana
Mohammed S
MS
Motawia
Catherine
C
Hervé du Penhoat
Frans
F
van den Berg
Andreas
A
Blennow
Serge
S
Perez
Søren B
SB
Engelsen
D000687:Amylopectin / Q000737:chemistry*; D016880:Anisotropy; D002236:Carbohydrate Conformation; D002240:Carbohydrate Sequence; D005936:Glucans / Q000737:chemistry; D006027:Glycosides / Q000737:chemistry*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D019906:Nuclear Magnetic Resonance, Biomolecular; D012996:Solutions; D013816:Thermodynamics; D014867:Water / Q000737:chemistry*
D005936:Glucans; D006027:Glycosides; D012996:Solutions; D014867:Water; D000687:Amylopectin