Book excerpt: Small biomolecule systems were interrogated using infrared multiple photon dissociation (IRMPD) action spectroscopy and corresponding quantum chemical calculations with a particular focus on peptide fragmentation and protonation site preference. b2+ and b3+ fragment ions with a terminal lysine homolog residue were investigated using IRMPD in the fingerprint region (1000 cm-1 – 2000 cm-1) and a variety of computational methods. We present the first spectroscopic confirmation of b-ion formation with a lactam structure. Infrared spectra for b2+ fragment system indicate the presence of a mixture of structures, though final determination will require further investigation. The b3+ fragment ion infrared spectra show strong support for the presence of a predominantly lactam structure. Extensive computational research in this system suggests the B3LYP method to be the most computationally efficient density functional theory method for spectral predictions. However, the inclusion of p-polarization into the basis set yielded inconclusive results and should be investigated further.