“…Side-by-side type interhelical associations may also occur since the measured height on the image was over 1 nm on average. If this is the case, trace amounts of kappa fraction in the sample influence the interhelical associations greatly because the cation selectivity or specific cation binding for native iota-carrageenan is ascribed to kappa-fraction impurities (Piculell, Nilsson, & Strom, 1989;Piculell & Rochas, 1990) and small amounts of kappa-fraction, whether added or present as impurities, govern the rheological properties of iota-carrageenan (Piculell, Nilsson, & Muhrbeck, 1992). The interhelical associations are negligible, however, because the associations hardly occurred in the presence of KCl (see below) in spite of K + being the most effective cation to promote the associations for kappa-carrageenan.…”