Solid-phase peptide synthesis is an indispensable method for constructing natural and modified peptide sequences. But the multistep process, even when automated, is extremely time-consuming for the relatively small amount of peptide generated. For example, a milligram-scale synthesis of a peptide 20 amino acids long can take 24 hours or longer to complete.
An MIT research team including Mark D. Simon, Klavs F. Jensen, and Andrea Adamo and led by Bradley L. Pentelute has developed a high-efficiency continuous-flow reactor system that produces similar quantities of high-purity peptides in just an hour (ChemBioChem 2014, DOI: 10.1002/cbic.201300796).
Peptides are in high demand because they can be designed for very specific functions inside cells. “Peptides are ubiquitous,” Pentelute says. “They’re used in therapeutics, found in hydrogels, and used to control drug delivery. They’re also used as biological probes to image cancer. Being able to access peptides more quickly will enable researchers to start doing things they couldn’t do before.”
Solid-phase peptide synthesis involves attaching a protected amino acid to a polymer bead and then carrying out painstaking deprotection and coupling steps to add amino acids one at a time to the end of the growing peptide chain. Rather than carrying out discrete steps as automated peptide synthesizers do, the MIT system constructs peptides as reagents continuously flow across the polymer beads in the reactor.
As the amino acid building blocks are selected and approach the 2.5-mL reaction chamber, they travel through a coil where they are preheated to 60 °C in seconds. The preheating accelerates peptide coupling, and fast passage through the reactor minimizes decomposition of the activated amino acids.
The team has used the system to make dozens of different peptides. Taking the work a step further, Surin K. Mong and Alexander A. Vinogradov in Pentelute’s group used the flow system to connect synthesized peptides to form proteins, including a 113-amino-acid antibody mimic and a 130-amino-acid bacterial enzyme (ChemBioChem 2014, DOI: 10.1002/cbic.201300797).
The MIT researchers have patented the technology and received support from MIT’s Deshpande Center for Technological Innovation to help commercialize it. “Our aim is to have next-day or two-day delivery of peptides to anyone in the world—that’s really the dream,” Pentelute says.
Providing a testimonial for the flow synthesis, chemical biology professor Isaac J. Krauss of Brandeis University comments that the new reactor allows optimization of long peptide syntheses that “just isn’t practical with slower instruments.” Krauss set up one of the MIT systems in his lab to produce glycopeptides for HIV vaccine development.
“We had no synthesizer of our own and had failed miserably to produce our desired 40-mer peptides in several attempts using a friend’s conventional and microwave peptide synthesizers,” Krauss says. “With Pentelute’s system, we were able to rapidly optimize many of the problematic steps in our synthesis in the space of a couple weeks.”