Understanding the correlation between composition, structure, properties and functional role of biomolecules is at the very heart of biochemistry and biophysics. The first step in this hierarchy, i.e. the connection between composition and structure has thus attracted enormous interest both in the case of e.g. entire proteins as well as for smaller peptides. The latter are especially interesting in view of reducing the complexity of natural systems and studying smaller-size models under controlled conditions. Furthermore, peptides made of few amino acids have attracted much attention in recent years thanks to their promising and wide scope of applications, be it in the fabrication of biomaterials, the engineering of bio-mimetic compounds for catalysis or in drug design. Indeed, in addition to contributing to physiological health, peptides have brought about conclusive benefits as anti-infective drugs due to their antimicrobial activity, leading to intense efforts in therapeutics development with peptidomimetic systems. The study of gas-phase peptides alone or with a defined number of solvent molecules constitutes a first step towards the understanding of the in vivo properties and allows for a differential picture of well-controlled intramolecular interactions separated from their combination with condensed phase and intermolecular effects. Moreover, in some cases, the experimentally produced gas-phase systems are able to retain solution-phase features so that scrutinizing native forms in the gas phase and at near zero temperature can provide valuable insight into remanent condensed phase interactions. Experimentally, advances over the last decade have coupled laser desorption and supersonic molecular beam cooling to capture IR spectra of neutral biomolecules in the gas phase. Alternatively, combinations of electrospraying, ion-mobility selection, mass spectrometry and cryogenic ion traps were reported to separate between conformational families of charged molecules prior to e.g. IR measurements. In particular, such experiments performed at cryogenic temperatures have been able to produce vibrationally-resolved and conformer-selective measurements; but due to the high intrinsic complexity, the identification of the underlying structures and the full assignment of the observed IR spectra can only be achieved with the support of computational methods. In turn, the experimental low-temperature data provides highly sensitive benchmarks for the assessment of the performance of computational methods for bio-relevant systems where the availability of accurate quantitative data is often sparse and hard to obtain. Therefore, the present work also illustrates a sensitive test case of the complementarity between simulations and experiments.