Enhancing effect of phenylboronic acid compounds and their interactions with the diol groups of saccharides in a capillary electrophoresis-chemiluminescence detection system.

In our previous study, we proposed molecular recognition of mono- and disaccharides making use of the interaction between their diol groups and p-iodophenylboronic acid in capillary electrophoresis with a chemiluminescence detection system. Here, to extend our knowledge of molecular recognition, we first examined the enhancing effects of four phenylboronic acid compounds other than p-iodophenylboronic acid i.e., 4-biphenylboronic acid, 4-octyloxyphenyl-boronic acid, 3-octyloxyphenylboronic acid, and 4-dodecyloxyphenylboronic acid, for luminol-hydrogen peroxide-horseradish peroxidase reaction in the capillary electrophoresis-chemiluminescence detection system. Only 4-biphenylboronic acid showed an enhancing effect similar to that of p-iodophenylboronic acid; the effect was determined over the range of 0.5-10 microM in this system. Second, we estimated the apparent stability constants between the diol groups of saccharides (1-methyl-D-glucoside, D-saccharose, and D-fructose) and the boronic acid moieties of the two enhancers, p-iodophenylboronic acid and 4-biphenylboronic acid. The apparent binding constants obtained here provided insight to confirm the principle of molecular recognition for the saccharides examined here.