Colour-Monitored Solid-Phase Multiple Peptide Synthesis under Low-Pressure Continuous-Flow Conditions. Synthesis of Medium-Size Peptides: The Propart of Human Procathepsin D and the Growth-Hormone Releasing Factor

The synthesis of two medium-size peptide amides, the propart of human procathepsin D (1-45) and the bovine growth-hormon releasing factor (1-44) has been accomplished by the solid-phase multiple peptide synthesis under low-pressure continuous-flow conditions on standard methylbenzhydrylamine polystyrene-based resin in concatenated flow reactors with adjustable volume. The completeness of acylation of resin-bound free amino groups was monitored by the acid-base indicator bromophenol blue. The efficiency of the coupling reaction was increased by exposure to elevated temperature in an ultrasonic bath. Crude peptides were purified on a mass-overloaded Vydac C18 reversed-phase semipreparative HPLC column. The synthetic propart of human procathepsin D (1-45) exhibited inhibition activity to bovine cathepsin D and four other aspartic proteases. Significantly increased plasma concentration in gilts was determined after application of synthetic bovine growth-hormone releasing factor (1-44).