Polyelectrolytes from seaweeds


Most algal extracellular polysaccharides, such as agar, carrageenan, furcellaran and alginate, contain anionic groups fixed to the glycan chains . These are important both for technical uses and for their biological properties . The polysaccharides are present in the intercellular space in the alga, and one biological function must be to keep this space in a swollen state . Because marine algae do not have any elaborate transport system for water and nutrients, as have the terrestrial plants, it is essential that each cell be surrounded by seawater and that the diffusion flux of water and nutrients be rapid . The counterions of the fixed charges, which must be present in the intercellular space for electrostatic reasons, constitute many particles, thus lowering the chemical potential of water and increasing the swelling of the polymer matrix . Another obvious biological function of the intercellular polysaccharides must be to cement the cells together and give certain mechanical properties to the plants . Studies of the mechanical properties of brown algae have shown that alginate contributes importantly to the rigidity of the plants, and that the rigidity is dependent upon both the chemical composition of the alginate and the ionic composition of the ambient water (Andresen, et al. 1977) . The way in which alginate simultaneously keeps the intercellular space in a swollen state and gives the tissue the required properties is by being present as a gel. Fig . 1 . shows an electron micrograph of a section of Laminaria hyperborea stipe, where a chain network with pores ranging in size from about 5 to 20 nm is clearly seen . Much less is known about the structural function of the charged polysaccharides in red algae, but it is

DOI: 10.1007/BF00027634

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Cite this paper

@article{Smidsrd2004PolyelectrolytesFS, title={Polyelectrolytes from seaweeds}, author={Olav Smidsr\od and Hans Grasdalen}, journal={Hydrobiologia}, year={2004}, volume={116}, pages={19-28} }