NEW LIGANDS FOR BORONATE AFFINITY-CHROMATOGRAPHY

A new type of boronate affinity ligand was synthesized which contained an internal coordinate bond between a carbonyl oxygen and a boron ato m. This coordination makes the boron atom tetrahedral, which is favora ble for boronate esterification with cis-diols. The ligand formed a ca techol ester in 2-(N-cyclohexylamino) ethanesulfonic acid, Tris and ph osphate buffers, respectively, at 0.5, 0.6 and 1.1 pH units lower than did phenylboronic acid. When the ligand was coupled to an agarose gel , the new matrix esterified with catechol at pH 7.5. When the ligand w as coupled to a cellulose gel, the new matrix esterified with catechol at pH 7.0. In comparison, the commercial m-aminophenylboronic acid-ag arose does not form an ester with catechol below pH 8.0.