Negatively-charged helices in the gas phase.

A polyalanine-based peptide which forms a stable, negatively-charged α-helix in the gas phase is reported. Addition of an N-terminal acidic residue forms a stabilizing hydrogen bond network and an electrostatic interaction with the helical dipole. Formation of this secondary structure was demonstrated using ion mobility-mass spectrometry and molecular modelling techniques. [ABSTRACT FROM AUTHOR]