Calculated ESP distribution of the five isolated oligosaccharides. The distribution of ESP was calculated for each isolated oligosaccharide, and electronegative (yellow) and electropositive (blue) zones are shown. A, ΔA-iB-iB; B, ΔE-D-A-D; C, ΔE-D-iA-D; D, ΔC-C-A-C; and E, ΔC-A-A-A. The putative PTN-binding oligosaccharides, ΔE-D-A-D and ΔE-D-iA-D, have spreading electronegative zones at iso values of −0.5 to −0.7 and even ΔA-iB-iB had a small electronegative zone at −0.7. In contrast, the non-binding octasaccharides, ΔC-C-A-C and ΔC-A-A-A, had no electronegative zones at −0.7. The spread of the electronegative zones for the PTN-binding oligosaccharides was larger than that for the non-binding oligosaccharides at the same iso values. The iso values are 0.5, 0.6, and 0.7 eV for the iso surface of the electropositive zones and −0.5, −0.6, and −0.7 eV for that of the electronegative zones.