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Published on 12/02/2025
For peptide synthesis in organic solvents, a wealth of polystyrene-based resins is on the market. However, for applications in aqueous media, only a limited number is available, especially since the well-established and appreciated PEG-based ChemMatrix® resins have been discontinued. Facing the quest to develop “greener” approaches by avoiding solvents such as DMF, which are harmful for the environment and human health, researchers and industry are eagerly searching for novel resins which are compatible with water and aqueous solvent mixtures.
Here, our novel, hydrophilic polyacrylamide-based Amino-Li resin comes into play: Li resin (named after its inventor Dr. Yongfu Li) is dedicated to the solid phase synthesis of peptides (SPPS) with Fmoc/tBu chemistry. It shows high swelling and is compatible with a broad range of solvents, even polar ones and also water, e.g., in combination with our Smoc-protected amino acid building blocks (Smoc = 2,7-disulfo-9-fluorenylmethoxycarbonyl).
Li resin is made from N,N-dimethylacrylamide cross-linked with N,N'-bis(acryloyl)piperazine and functionalized with 1-[1-(N-acrylyl)piperidin-4-yl]methanamine. Polymerization takes advantage of a proprietary technology to produce fibers which are similar in size to bead resins but have a larger surface area. The resin structure provides a loading capacity of around 0.4-0.6 mmol/g. For polar solvents, the swelling is about 4 ml/g in ACN, 6 ml/g in DMF, DMSO and NBP, about 7 ml/g in water, and about 8 ml/g in DCM and IPA. With >80%, yields obtained with Li resins have been reported to be significantly higher compared to those for the discontinued ChemMatrix® resins.
Chemical structure of Li resin: N,N-dimethylacrylamide, N,N’-bis(acryloyl)piperazine and 1-[1-(N-acrylyl)piperidin-4-yl] methanamine are the ingredients for Amino-Li Resin (BR-1045), which is the base material for our preloaded MPPA-Li Resins and manufactured following a proprietary protocol to ensure the required mechanical properties.
In addition to our Amino-Li base resin (BR-1045), we are now offering a derivative carrying a Fmoc-Rink linker (BR-5281) as well as amino acid-MPPA-preloaded resins (see related products at the end of this page). The oxymethylphenoxy propionic acid (MPPA) moiety serves as sort of Wang linker with the advantage of reducing racemization of the C-terminal amino acid and the formation of dimers (which is a notorious problem of para-hydroxymethyl resins) to typically less than 0.5%.
Pre-loaded Li resins. Left: Amino-Li resin (grey) decorated with the Fmoc-protected Rink linker (green). Right: Amino-Li resin carrying a fluorenylmethoxycarbonyl (Fmoc)-protected amino acid (orange) connected via a MPPA linker (green).
For efficient handling, it should be noted that acrylamide-based resins in general are less robust against mechanical stress than resins made from polystyrene. Li resin suspensions therefore should be gently shaken and drained by gravity, as the forces of mechanical stirring and vacuum filtration tend to collapse the fibers, and the resulting fines can affect the rheological properties of the resin and clog the frit of the reaction vessel.
Besides the production of peptides, the resin with the peptide still attached may be used for, e.g., the purification of antibodies or ligands by affinity chromatography, or for the on-resin-screening of chemical libraries.
→ You need more information on resins for SPPS? Download our Resin Guideline!
→ You want to learn more about peptide synthesis in aqueous solution (ASPPS) using Smoc-protected amino acids and Li resin? Read this paper!
→ For more infos about MPPA-amino acids, see our previous blog!
References:
Improved approach for anchoring Nalpha-9-fluorenylmethyloxycarbonylamino acids as p-alkoxybenzyl esters in solid-phase peptide synthesis; F. Albericio, G. Barany; Int. J. Peptide. Protein. Res. 1985; 26(1): 92-97. https://doi.org/10.1111/j.1399-3011.1985.tb03182.x
A Practical Peptide Synthesis Workflow Using Amino-Li-Resin; D. C. Akintayo, S. Rao Manne, B. G. de la Torre, Y. Li, F. Albericio; Methods Protoc. 2022; 5(5): 72-84. https://doi.org/10.3390/mps5050072
Amino-Li-Resin—A Fiber Polyacrylamide Resin for Solid-Phase Peptide Synthesis; D. C. Akintayo, B. G. de la Torre, Y. Li, F. Albericio; Polymers 2022; 14(5): 928-42. https://doi.org/10.3390/polym14050928
Novel amino-Li resin for water-based solid-phase peptide synthesis; C. Uth, S. Englert, O. Avrutina, H. Kolmar, S. Knauer; J. Pept. Sci. 2023; 29(12): e3527. https://doi.org/10.1002/psc.3527
A Practical Peptide Synthesis Workflow Using Amino-Li-Resin; D. Caleb Akintayo, S. R. Manne, B. G. de la Torre, Y. Li, F. Albericio; Methods Protoc. 2022; 5(5): 72. https://doi.org/10.3390/mps5050072
