Accessible conformations of the β-d-(2→1)- and -(2→6)-linked d-fructans inulin and levan

✍ Scribed by Alfred D. French

• Publisher: Elsevier Science
• Year: 1988
• Tongue: English
• Weight: 780 KB
• Volume: 176
• Category: Article
• ISSN: 0008-6215
• DOI: 10.1016/0008-6215(88)84054-0

✦ Synopsis

Accessible conformations of the linear D-fructofuranans inulin having P-D-(2+1) and levan (phlein, or phlean) /I-~-(2--+6) linkages were surveyed with the computer program NHMAP. This program rates individual conformations as allowed if a model can meet glycosidic bond-angle and hard-sphere, interatomicdistance criteria. Molecules of D-fructofuranose have two primary alcohol groups that can rotate, changing the positions of the hydroxyl groups on C-l and C-6. The C-1-0-1 bond is part of the backbone of inulin, and the C-6-O-6 bond is similarly part of levan. Through steric interference, the other such group also affects the possible conformations of the polymer. Including rotations of both primary alcohol groups in conformational analyses requires substantially more computer time than is needed for simpler polysaccharides. Each polymer has three single bonds that link the fructofuranose rings, and rotations about these bonds permit a large variety of molecular shapes. Despite this degree of molecular flexibility, the use of various starting, monomeric-ring geometries further expands the range of allowed polymeric shapes. Models of both polymers can be either right-or left-handed, although more right-handed models of inulin were allowed; most levan models were found to be left-handed. The depiction of allowed shapes for inulin is similar to one previously published for dextran.