Enhancing the Efficiency of the Solid Phase Peptide Synthesis (SPPS) Process by High Shear Mixing

Abstract

The brittle nature of the polymer beads used in SPPS dictates mild mixing techniques with low mass transfer. We demonstrate that vigorous overhead mechanical stirring with superior mass transfer properties kept the beads intact and significantly accelerates reaction kinetics and efficiency.

The breaking beads approach for photocleavage from solid support

“…Each irradiation was performed for four hours and after each irradiation experiment, the cleavage efficiency was determined using a standard Fmoc quantification analysis (Figure 3). 33,34 This analysis showed that increasing the stirring rate improves cleavage efficiency. Stirring at 1060 rpm for four hours provided a cleavage of over 80%.…”

“…A recent report suggested that after stirring polystyrene beads with a magnetic bar, the crushed beads are much smaller than the original mesh size but are still big enough to be separated from the cleaved product by a simple filtration of the solution. 32,33 We thought that crushing the beads during the irradiation will increase the surface area exposed to light and might improve cleavage efficiency while it will not hamper the simple filtration separation process. Herein, we present a simple benchtop light-emitting diode (LED) batch system for photocleavage from solid support.…”

Diffusion Enhanced Amide Bond Formation on Solid Support

“…This specific mixing setup rely on high shear forces to increase diffusion and we termed it High Shear Stirring (HSS). 20 Studies of coupling reaction in a shaker vs. HSS. We compared the efficiency of coupling using conventional mixing in an oval shaker at 100 rpm to HSS performed using mechanical overhead stirring at 700 rpm.…”

“…Most importantly, we demonstrated that overhead mechanical stirring, contrary to magnetic mixing, does not lead to the destruction of the polystyrene beads even at 700 rpm. 20 In addition, we showed that high shear stirring results in faster and more efficient swelling of the polystyrene beads that also contributes to an increase in diffusion. Amide bond formation is one of the most common reactions in organic synthesis.…”

“…18,19 In our recent study, we used high shear mechanical stirring to improve Fmoc removal on solid support. 20 The enhanced mass transfer, achieved by applying fast mixing, increased the Fmoc removal rate and allowed us to decrease the amount of piperidine by 75% compared to the state-of-the-art ( Figure 1). Most importantly, we demonstrated that overhead mechanical stirring, contrary to magnetic mixing, does not lead to the destruction of the polystyrene beads even at 700 rpm.…”