Complex formation of polygalacturonic acid with chitooligosaccharides

We have examined the formation of polyelectrolyte complexes of polygalactur onic acid (PGA) with chitooligosaccharides [(GlcN)(n); n=1-6] in an acetic acid buffer solution (50 mM, pH=5.5) at 35 degrees C. PGA forms precipitate s of complexes with chitooligosaccharides [(GlcN)(n) ; n=4-6] with the stoi chiometric composition in regard to monomer units, although it forms no pre cipitate with (GlcN)(n)(n=1-3). The remarkable difference in the complex fo rmation of PGA between with (GlcN)(3) and with (GlcN)(4) may be principally due to the difference in the number and the orientation of amino groups be tween (GlcN)(3) and (GlcN)(4), because neighboring amino groups on both sid es of (GlcN)(4) can interact cooperatively with different PGA chains.