Supergiant ampholytic sugar chains with imbalanced charge ratio form saline ultra-absorbent hydrogels

A novel sugar chain (SC) with an ultrahigh molecular weight and an imbalanced charge ratio was extracted from the jellylike extracellular matrix (ECM) of a freshwater unicellular cyanobacterium, Aphanothece Sacrum. Fourier transform ion cyclotron resonance mass spectroscopy (FT-ICR-MS) analyses of the extracted SC demonstrated the presence sulfated muramic acid as a chain constituent, which indicates that the SC, was novel. These sugar chains, named sacran, was observed to be an extremely high molecular weight polysaccharide composed of a high content of anionic sugars with a low content of cationic sugars. Sacran were soluble in hot water to give a homogeneous solution regardless of pH and formed a physical hydrogel after cooling. Atomic force microscopy of sacran revealed that the sacran gels formed network structures containing nanolooped chains which exhibited a salt-induced transformation into extended rodlike chains.