Sugar-binding property of magnetite particles modified with dihydroxyborylphenyl groups via graft polymerization of acrylic acid

In order to combine sugar-binding property and magnetism, dihydroxyborylphenyl (DHBP) groups were attached to magnetite particles via graft polymerization of acrylic acid. The graft polymerization was carried out in a redox system consisting of mercapto groups introduced onto the surfaces of magnetite particles and ceric ions. DHBP groups were attached through amide linkages by the condensation reaction of 3-aminophenylboronic acid with carboxyl groups of the grafted poly(acrylic acid). Complexation of the attached DHBP groups was examined with various sugars and compared with that of the free phenylboronic acid. The attached DHBP groups gave a large value of binding constant K for the complexation with adenosine having a pair of cis-OH groups, whereas the K values for the DHBP groups with adenosine phosphates were extremely small. With respect to the complexation with 2′-deoxyadenosine, cooperative interaction of neighboring DHBP groups was suggested. Although the value of acidity index pKa of the attached DHBP was larger than that of free phenylboronic acid, the pKa value was decreased by coexistent basic groups.