PEPTIDES & PROTEINS

Note : Dotted line - UV absorption ; Solid line -VBFR change in volume

Figure 3 – Deprotection & coupling cycle dynamically adjust the internal volume of the reactor . We have developed three different reactor volumes that make it possible to scale up SPPS from 100 mg to gramscale . Figure 2 shows the Vapourtec Variable Bed Flow Reactor ( VBFR ), along with its reactor controller unit , which adjusts the reactor ’ s volume , with a resolution of ± 0.5 µ l , to deliver a constant packing density . By combining the control that flow chemistry possesses and keeping the resin to its minimum volume throughout the sequences , a more efficient synthesis is achieved . This is of particular relevance when nonnatural amino acids are used , as they are more expensive than standard protected amino acids . Our collaborators at the Max Planck Institute in Germany have successfully demonstrated the potential of the VBFR for SPPS . This ranges from synthesising a 26-mer peptide with 91 % purity to synthesising a difficult peptide , JR10-mer , also with high purity .

The implementation of smart reactors does not only lead to an improvement in the synthesis and final crude purity . It is also a tool for the peptide chemist to learn about that synthesis . As the reactor adapts its volume to accommodate the mass changes on the resin , it records the evolution of internal volume over time . When this set of data is then overlapped with UV data , a much clearer analytical picture is formed . Figure 3 shows a typical set of data for a deprotection and coupling cycle . This valuable inline dataset makes it possible to evaluate when an aggregation event occurs or when a reaction has not performed as it should .

Conclusions

Both industry and academia now have years of expertise in flow chemistry . As their knowledge has further expanded , so has their field of application . Transferring batch processes into flow protocols is a daily routine for any experienced flow chemist but remains a challenge for researchers with less experience in flow . This is harder still with SPPS , as transferring a batch protocol into flow still remains a challenge . When combining flow systems and dynamic reactors , SPPS not only becomes a reality , it opens the door for a deeper understanding of the chemical processes involved in peptide synthesis . With the wide range of synthesis scales , it enables the optimisation of protocols at 100 mg-scale , saving reagents and reducing scale-up risks , with no need for dedicated equipment , other than a Vapourtec flow chemistry system . •

J j

Dr Manuel Nuño

RESEARCH SCIENTIST

VAPOURTEC manuel . nuno @ vapourtec . com www . vapourtec . com

References

JAN / FEB 2021 SPECCHEMONLINE . COM

51