Abstract
Numerous studies have suggested that the n→π* interactions between carbonyls could contribute significantly to the stability of proteins. Nevertheless, their evaluation is challenging because of the solvent environment or crystal packing forces in solids. Here we study the rotational spectrum of HGlyProOH dipeptide, a very common sequence found in collagen, the most abundant protein in vertebrates, in isolated conditions. Three different structures are unequivocally characterized in the gas phase. Interestingly, the most abundant structure is stabilized by an n→π* interaction and adopts the same conformation as is found in crystalline collagen. This observation serves to support the importance of the n→π* interactions between carbonyl groups.
Highlights
Numerous studies have suggested that the n→π* interactions between carbonyls could contribute significantly to the stability of proteins
We present evidence in gas phase that unambiguously confirms the relevant role that the n → π* interaction has between carbonyls, which manifests even in a small system such as the HGlyProOH dipeptide
The two-body collision with the carrier gas should cool the stable conformers to very low temperatures, thereby trapping them in their energy minima. Those with sufficient population can be probed in the supersonic expansion by Fourier transform microwave spectroscopy
Summary
Numerous studies have suggested that the n→π* interactions between carbonyls could contribute significantly to the stability of proteins Their evaluation is challenging because of the solvent environment or crystal packing forces in solids. The structural features and folding mechanisms of polypeptides and proteins arise from a complex and subtle balance of different interactions, fundamental as a whole and at the molecular level Their architecture is sustained by a fragile combination of inter- and intramolecular noncovalent interactions in the polypeptide chains[1]. The Raines group has suggested that numerous residues in folded proteins are oriented to take advantage of this energy release, inferring that n → π* interactions between carbonyls could contribute significantly to the three-dimensional structure and conformational stability of proteins[7,8,9,10,11,12,13]. Either they overestimate the strength of the n → π*
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