| Proteolytic enzymes have been used for the synthesis of homo-oligomers and hydroxy acid capped peptides with amino acids and hydroxy acid esters as substrates in aqueous and aqueous organic biphasic and triphasic systems. However, successful incorporation of hydroxy acids in oligopeptide substrates has not been demonstrated. Use of monophasic media comprising of acetonitrile/water in which oligopeptide substrates were soluble was examined for the synthesis of oligomers of neutral and polar amino acids like Met, Tyr, Lys, Gly, Asp and Glu and tailored co-oligomers of Lys-Met and Arg-Met. Effect of reaction parameters such as starting substrate concentration, system composition, reaction time, temperature, and time of addition of second substrate on the peptide synthesis process was evaluated. The HPLC and ESI-MS characterization revealed the formation of oligomers and co-oligomers in yields of ∼80%. Results also show that systematic change of reaction media composition and sequential addition of amino acid substrates would serve as the best approach for the synthesis of co-oligopeptides of Lys-Met and Arg-Met in acetonitrile/water system.; Use of anti-oxidants during oligomerization is essential. Traditionally mercaptoethanol has been used. However, because of their toxicity, such anti-oxidants pose a problem for utilization. To over come this, the effectiveness of L-Cysteine as an anti-oxidant for protease catalysis was also evaluated. Results show that L-Cysteine can be used as an effective replacement for mercaptoethanol in peptide synthesis. Finally, hydroxy acid capping of peptides was carried out in acetonitrile/water system. Results show that oligopeptides of Met, Phe and Insulin could be readily capped with a hydroxy acid in a monophasic system comprising of acetonitrile/water. |
