ABSTRACT
Galactans are the main matrix polysaccharides in most o f the Rhodophyceae. Essentially, they consist o f linear chains o f alternating 3-linked /3galactose residues (A units) and 4-linked a-galactose residues (B units) [1]. The A units always belong to the D-series, whereas the B units may include residues o f the d - or the L-series. These structures are usually masked by substitution with sulfate esters, pyruvic acid ketals, methoxyl groups, a 3,6-anhydro ring on the B unit, and variable length side chains [1]. A l though these substitutions may produce several combinations, yielding rad ically different polysaccharides, the simplicity o f a common backbone allows a clear classification to be made on the basis o f the configuration o f the B units: carrageenans if they belong to the D-series, agars for those with L-configuration, and the so-called “intermediate”, hybrids with d - and L-galactose B units interspersed on the same molecules [1]. This simple arrangement allows for the placement o f “corallinans” and other unusual polysaccharides within the galactan scheme, in spite o f the complicated pattern arising from substitution.
