On the Helix-coil Transition in Alanine-based Polypeptides in Gas Phase

TL;DR

This study uses multicanonical simulations to explore how charged end groups influence helix formation in alanine-based polypeptides in gas phase, confirming known behaviors and revealing effects of terminal charges.

Contribution

It demonstrates how charged end groups affect helix stability and transition temperatures, providing insights into intramolecular interactions in gas-phase polypeptides.

Findings

Neutral polyalanine shows a clear helix-coil transition.

Charged Lys+ at C terminal stabilizes helix and raises transition temperature.

Charged Lys+ at N terminal inhibits helix formation, leading to globular structures.

Abstract

Using multicanonical simulations, the authors study the effect of charged end groups on helix formation in alanine based polypeptides. They confirm earlier reports that neutral polyalanine exhibits a pronounced helix-coil transition in gas phase simulations. Introducing a charged Lys+ at the C terminal stabilizes the helix and leads to a higher transition temperature. On the other hand, adding the Lys+ at the N terminal inhibits helix formation. Instead, a more globular structure was found. These results are in agreement with recent experiments on alanine based polypeptides in gas phase. They indicate that present force fields describe accurately the intramolecular interactions in proteins.