Peptides are limited in their use as drugs due to low cell permeability and vulnerability to proteases. In contrast, peptoids are immune to enzymatic degradation and some peptoids have been shown to be relatively cell permeable. In order to facilitate future design of peptoid libraries for screening experiments, it would be useful to have a high-throughput method to estimate the cell permeability of peptoids containing different residues. In this paper, we report the strengths and limitations of a high-throughput cell-based permeability assay that registers the relative ability of steroid-conjugated peptides and peptoids to enter a cell. A comparative investigation of the physicochemical properties and side chain composition of peptoids and peptides is described to explain the observed higher cell permeability of peptoids over peptides. These data suggest that the conversion of the monomeric residues in peptides to an N-alkylglycine moiety in peptoids reduced the hydrogen-bonding potential of the molecules and is the main contributor to the observed permeability improvement.
Bibliographical noteFunding Information:
This work was supported by a contract from the National Heart Lung and Blood Institute Proteomics Center Program (NO1-HV-28185) and the Welch Foundation (I-1299). We thank Dr. Xian-Jin Xie from the Division of Biostatistics, Department of Clinical Sciences for assistance in the statistical analyses, and Dr. Hyun-Suk Lim for constructive discussions, both at the University of Texas Southwestern Medical Center.
- Cell permeability
- Cell-based assay
- High-throughput assay
- High-throughput cell permeability assay
- Physicochemical properties
- Solid-phase synthesis combinatorial library