Effect of the Mobility of Ligands in Polyrotaxanes on Order Structure of Water Clusters

Abstract

The effect of the mobility of ligands (maltose groups) in the polyrotaxanes (pRXs) on the structure of the surrounding water molecules was investigated. Raman spectra of collective OH stretching vibration of water molecules in aqueous solutions of maltose-pRX conjugates with different alpha-cyclodextrin (alpha-CD) threading on a poly(ethylene glycol) (PEG) chain was measured. The mobility of maltose groups was estimated by measuring the relaxation time T2 of the C1 protons in maltose groups bound on alpha-CD by NMR experiment. A positive correlation between the Raman intensity of the collective band and the relaxation time T2 was obtained. This result indicates that the degree of order of the water clusters is higher as the mobility of maltose groups increases in these conjugate solutions. It is suggested that rapid motion of maltose groups in the pRX conjugate can contribute to preserving ordered structure of the bulk water clusters.

Cyclodextrin-based multivalent glycodisplays: covalent and supramolecular conjugates to assess carbohydrate–protein interactions

“…Experimental evidence to support this hypothesis was obtained initially by Raman spectroscopy 126 and further confirmed by advanced NMR studies. 125 The relatively high mobility of the Mal ligand in the rotaxane architecture additionally prevents the formation of ordered clusters of water molecules, avoiding the unfavourable energy term derived from breaking those clusters upon lectin binding. In 2010, Sasabe and coworkers extended Yui's approach for the synthesis of multivalent Z-protected tyrosine-capped glycopolyrotaxanes for the preparation of Mal-aCD-PRXs immobilized onto polystyrene (PS) microspheres (1-50 mm), with an average load of five maltosyl groups per aCD threaded unit (78,Scheme 33).…”

Crosslinked Network with Rotatable Binding Sites Based on Monocarboxylated α‐Cyclodextrin [2]Rotaxane Capable of Angiotensin III Recognition

“…[6] For such molecular recognition, because the spatiald istance of the intermoleculari nteraction between the molecules to be recognized must be strictly controlled, functional monomers capable of intermolecular interactions, such as electrostatic interactions are copolymerized within ac rosslinkedp olymer; [7] however,i ti sd ifficult to strictly control spatial distances resulting from radical polymerization. Such the mobile motion in the rotaxanes tructure hasb een characterized by NMR spectroscopy, [10] quartz crystal microbalance with dissipation (QCM-D), [8c] and molecular dynamicss imulation. Such the mobile motion in the rotaxanes tructure hasb een characterized by NMR spectroscopy, [10] quartz crystal microbalance with dissipation (QCM-D), [8c] and molecular dynamicss imulation.…”

Molecular‐Recognition and Binding Properties of Cyclodextrin‐Conjugated Polyrotaxanes

“…[14] Herein, the conjugation of b-CD to the polyrotaxane may facilitate the mobility of the threaded a-CD to enhance sliding and rotation in aqueous solution.…”