Lipid Coated Catalytic Antibody in Water Miscible Organic Solvents

To date numerous publications have appeared on catalytic antibodies. Various reactions, such as hydrolysis of esters and amides, transesterifications, Diels-Alder reactions, decarboxylations, and sigmatropic rearrangements have been reported to be catalyzed by catalytic antibodies (40-46). Catalytic antibodies are induced to compounds (haptens) that mimic the transition states in these chemical reactions. Although substrates in these reactions are generally lipophilic and not very water soluble, the reactions have been always carried out in aqueous buffer solutions because catalytic antibodies are thought to be soluble and stable only in aqueous solution.

Deoxyadenosine (Y. 75%) Thymine (Y. 70%) Glycerol (Y. 85%)

Fig. 7. Chemical structures of the practical compounds obtained with phosphatidylation catalyzed by the lipid-coated PLD in two-phase benzene-acetate buffer solutions.

Deoxyadenosine (Y. 75%) Thymine (Y. 70%) Glycerol (Y. 85%)

Fig. 7. Chemical structures of the practical compounds obtained with phosphatidylation catalyzed by the lipid-coated PLD in two-phase benzene-acetate buffer solutions.

In an effort to make catalytic antibodies more attractive catalysts from a synthetic standpoint, we applied our lipid-coating method to solubilize catalytic antibodies in water-miscible organic solvents. The catalytic hydrolysis of monoester of chloramphenicol was chosen as an example, because the substrate is lipophilic and the catalytic reaction has been studied in aqueous solution (45,46).

Figure 8 shows the effect of the DMSO content of the buffer solution on hydrolysis rates at 30°C. DMSO must be added to a concentration of at least 20% to solubilize the lipophilic substrate completely. At concentrations of between 20% and 65% DMSO in buffer solution, both substrates and native or lipid-coated antibodies were homogeneously soluble, but the catalytic activity of the lipid-coated antibody was higher than that of the native antibody because the native was denatured by the DMSO. Similar denaturing was observed for other water-miscible organic solvents such as acetone, acetonitrile, and dimethylformamide.

Because catalytic antibodies are designed to catalyze a wide range of organic reactions with lipophilic substrates, it is important to use antibodies in water-miscible or hydrophobic organic solvents. The physical stability of the antibody is also expected to be increased by the coating lipids.

0 0

Post a comment