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X-ray structure of the cyclomaltohexaicosaose triiodide inclusion complex provides a model for amylose-iodine at atomic resolution

Item Type:Article
Title:X-ray structure of the cyclomaltohexaicosaose triiodide inclusion complex provides a model for amylose-iodine at atomic resolution
Creators Name:Nimz, O. and Gessler, K. and Uson, I. and Laettig, S. and Welfle, H. and Sheldrick, G.M. and Saenger, W.
Abstract:Cyclomaltohexaicosaose (CA26) is folded into two 1 2/3 turns long V-helices that are oriented antiparallel. Crystals of complexes of CA26 with NH 4I 3 and Ba(I 3) 2 are brown and X-ray analyses show that I 3 - units are located in the ∼5 A wide central channels of the V-helices. In the complex with NH 4I 3, two CA26 molecules are stacked to form 2×1 2/3 turns long channels harbouring 3 I 3 - at 3.66-3.85 A inter I 3 - distance (shorter than van der Waals distance, 4.3 A), whereas in the Ba(I 3) 2 complex, CA26 are not stacked and only one I 3 - each fills the V-helices. Glucose I contacts are formed with C5-H, C3-H, C6-H and (at the ends of the V-helices) with O6 in (+) gauche orientation. By contrast, O2, O3, O4 and O6 in the preferred (-) gauche orientation do not interact with I because these distances are ≥4.01 A and exceed the van der Waals I⋯O sum of radii by about 0.5 A except for one O2⋯I distance of 3.68 A near the end of one V-helix. Raman spectra indicate that the complexes share the presence of I 3 - with blue amylose-iodine.
Keywords:Amylose-Iodine, CA26, Cyclomaltohexaicosaose Triiodide Inclusion Complexes, Triiodide Inclusion Complex, X-Ray Structures
Source:Carbohydrate Research
ISSN:0008-6215
Publisher:Elsevier (The Netherlands)
Volume:338
Number:9
Page Range:977-986
Date:22 April 2003
Official Publication:https://doi.org/10.1016/S0008-6215(03)00016-8
PubMed:View item in PubMed

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