| Research Abstract |
We have found that water soluble polymer having phenylboronic acid moiety has ability to induce mouse lymphocytes proliferation. This might be due to the binding of phenylboronic acid residues in the polymer to sugar residues existing on the plasma membrane surface of lymphocytes. In this context, phenylboronate polymer serves as artificial mitogen of lymphocytes. phenylboronic acid is known to have an equilibrium between trigonal form and tetrahedral borate form in aqueous milieu. Only tetrahedral borate forms a stable complex with sugar. However, due to the relatively high pKa of phenylboronic acid, there exists only a small amount of tetrahedral boronate at physiological condition (pH7.4). To increase mitogenic activity under physiological condition, amino groups were introduced into the borate-containing polymer in this study to facilitate complex formation of boronate with sugar residues on the plasma membrane, allowing to achieve an increased ability to proliferate lymphocytes. Thus, ternary copolymer (DBA) of N,N-dimethylacrylamide, 3-acrylamidophenylboronic acid and N,N-dimethylaminopropylacrylamide (DMAPAA) was synthesized. Proliferative response of mouse lymphocytes was evaluated from incorporation of ^3H-thymidine. Remarkable increase in ^3H-thymidine uptake to lymphocytes was observed for lymphocytes cultured with DBA compared to that with DB which has no amino groups. This increase in mitogenic ability seems to be due to the effective formation of the complex between boronate and sugar residues on the cell membrane because of the coordination of amino groups to phenylboronic acid moieties in DBA.There was observed an optimum amino group content in the DBA copolymer in terms of lymphocyte proliferation, indicating a crucial role of amino group content of DBA in lymphocyte proliferation.
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