Andersson, AkeYatsyna, VasylLinares, MathieuRijs, AnoukZhaunerchyk, Vitali2023-03-132023-03-132023-03-132023-02-0210.1021/acs.jpca.2c07863https://infoscience.epfl.ch/handle/20.500.14299/195851WOS:000927063400001We investigate the gas-phase structure of the neutral pentaalanine peptide. The IR spectrum in the 340-1820 cm-1 frequency range is obtained by employing supersonic jet cooling, infrared multiphoton dissociation, and vacuum-ultraviolet action spectroscopy. Comparison with quantum chemical spectral calculations suggests that the molecule assumes multiple stable conformations, mainly of two structure types. In the most stable conformation theoretically found, the N-terminus forms a C5 ring and the backbone resembles that of an 310-helix with two beta-turns. Additionally, the conformational preferences of pentaalanine have been evaluated using Born-Oppenheimer molecular dynamics, showing that a nonzero simulation time step causes a systematic frequency shift.Chemistry, PhysicalPhysics, Atomic, Molecular & ChemicalChemistryPhysicsinitio molecular-dynamicsproton-bound dimersdensity-matrixirmpd spectroscopygaussian-orbitalspeptidespectraprolinehelixtext::journal::journal article::research article