Novel, cell-penetrating molecular transporters with flexible backbones and permanently charged side-chains

Abstract

Various cell-penetrating peptides have been discovered recently that can translocate across plasma membranes and can even carry large cargo molecules into the cells. Because under physiological conditions most of these peptides carry considerable positive charges due to the presence of basic amino acids such as arginine, we decided to investigate whether molecular transporters composed of permanently charged side-chains also possess such cell penetrating ability. Arginine-rich oligomers that have a backbone with increased flexibility due to incorporation of non-alpha-amino acids (epsilon-aminocaproic acid) have been found to be effective molecular transporters. Here, we report the preparation of analogue structures by replacing the arginine residues with the quaternary form of a novel redox amino acid (Nys(+)) that contain a trigonelline moiety; it has already been shown possible to replace the original basic amino acid side-chain of neuropeptides without significant activity-loss due to the sufficiently close steric and electronic analogy between the new Nys(+) and the original side-chains (in their protonated form, e.g., Arg(+), Lys(+)). A nonamer analogue showed transporter activity resulting in increased cellular uptake in human carcinoma (HeLa) cells.

Leptin‐based glycopeptide induces weight loss and simultaneously restores fertility in animal models

“…Consequently, in designing E1/Aca, we eliminated the Dap(Ac) moiety, and replaced the penultimate leucine with Aca, a similarly hydrophobic non‐natural amino acid residue. Aca has been used to control bleeding as a standalone drug, and when incorporated into peptides, is a promoter of molecular transport across cells and tissues [16]. Most O‐linked glycoproteins contain Thr‐linked α ‐GalNAc moiety, and accordingly, replacement of Ser β (Glc) with the more readily available Thr α (GalNAc) was expected to simplify the chemical peptide synthesis, and also reduce the immunogenicity of the product.…”

Cell-Penetrating Peptides: Design, Synthesis, and Applications

“…For example, when lysine residues are replaced with ornithine residues, the peptide becomes more resistant to cellular degradation. , Cargo delivery efficiency can also be improved by changing the structure of the peptides. For example, peptides have been modified into dendrimers, − cyclic peptides, and the often used strategy of modifying to the side chains of CPPs, as in the case of TP10 derivatives − developed by our group and depicted in Table . Each modification must be carefully designed to avoid problems that could lead to low synthesis yields, poor solubility, aggregation, or toxicity.…”

Development of Novel Peptides for Mitochondrial Drug Delivery: Amino Acids Featuring Delocalized Lipophilic Cations

“…The Zincke reaction to convert the primary amines into pyridyl salts was completed as described previously (24,25). The peptide was dissolved in MeOH (4°C) and added, dropwise, to a chilled solution of Zincke salt (5 equiv.…”

“…Once the reaction was completed (approximately 4 days), the peptide was precipitated by the addition of chilled Et 2 O and purified by HPLC as described above. The Zincke salt used in these reactions was synthesized as described previously (24,25). Briefly, pyridine (2 equiv.)…”