The Yin and Yang of How N-Terminal Acyl Caps Affect Collagen Triple Helices

N-terminal acylation is a common tool for the installationof functionalmoieties (e.g., sensors or bioactive molecules) on collagen modelpeptides (CMPs). The N-acyl group and its lengthare generally assumed to have little or no influence on the propertiesof the collagen triple helix formed by the CMP. Here, we show thatthe length of short (C-1-C-4) acyl cappinggroups has different effects on the thermal stability of collagentriple helices in POG, OGP, and GPO frames. While the effect of differentcapping groups on the stability of triple helices in the GPO frameis negligible, longer acyl chains stabilize OGP triple helices butdestabilize POG analogues. The observed trends arise from a combinationof steric repulsion, the hydrophobic effect, and n -> pi* interactions. Our study provides a basis for thedesign of N-terminally functionalized CMPs with predictable effectson triple helix stability.