Rapid binding of concanavalin A and maltose-polyrotaxane conjugates due to mobile motion of alpha-cyclodextrins threaded onto a poly(ethylene glycol).

Maltose-polyrotaxane conjugates (Mal-PRXs), in which maltose-conjugated alpha-cyclodextrins (alpha-CDs) are threaded onto a poly(ethylene glycol) (PEG) chain capped with benzyloxycarbonyl-L-tyrosine, were characterized in terms of their molecular motion and the relation to multivalent interactions between the maltose moiety and concanavalin A from Canavalia ensiformis (Con A). Spin-lattice relaxation time (T1) and spin-spin relaxation time (T2) of alpha-CD C(1), maltosyl C(1), and PEG methylene protons in the Mal-PRXs revealed that the mobile motion of alpha-CDs in the polyrotaxane governed the molecular motion of maltosyl groups in alpha-CDs and threading PEG chain. The association constant (Ka) of the Mal-PRXs with 22, 38 and 53% of alpha-CD threading was 5.7 x 10(4), 1.1 x 10(6), and 5.3 x 10(5) (M(-1)-maltose), respectively. The largest Ka value of the Mal-PRX with 38% of alpha-CD threading was well correlated with the T1 and T2 values of maltosyl groups and alpha-CD, suggesting that the mobile motion of maltose-conjugated alpha-CDs in the Mal-PRX contributes to the highest affinity with Con A. Initial rate of binding with Con A was also governed by the mobile motion of maltose-conjugated alpha-CDs. Therefore, we concluded that both highly molecular motion due to the mobile motion of maltose-conjugated alpha-CDs and multivalency of the Mal-PRXs contributes to inducing rapid Con A binding.