The molecular structure of kappa-carrageenan and comparison with iota-carrageenan

✍ Scribed by Rick P. Millane; Rengaswami Chandrasekaran; Struther Arnott; Iain C.M. Dea

• Publisher: Elsevier Science
• Year: 1988
• Tongue: English
• Weight: 982 KB
• Volume: 182
• Category: Article
• ISSN: 0008-6215
• DOI: 10.1016/0008-6215(88)84087-4

✦ Synopsis

The ordered conformation of kappa-carrageenan molecules in condensed but well-hydrated systems has been investigated by refining stereochemically plausible models to fit the continuous X-ray diffraction data obtained from oriented fibers . In the best model, the molecules are coaxial duplexes comprising right-handed, 3-fold helical chains of pitch 25 .0 A . As with iota-carrageenan, the chains are parallel but their juxtaposition in kappa-carrageenan is significantly different since they are offset from the half-staggered arrangement by a 28° rotation and a 1 .0-A translation . Alternative models (single helices, coaxial duplexes containing 6-fold chains, noncoaxial dimers, and mixtures of single and double helices) are quite incompatible with the diffraction data . Some antiparallel, coaxial duplex models approach the best model either in stereochemical plausibility or fit with the diffraction data, but none is as convincing overall as the best (parallel-stranded) model .