@entity68570 -water clusters can be considered as appropriate models for investigating the interaction of the peptide functional group with water. The rotational spectra of 2-azetidinone-(H2O)n (n = 1, 2) complexes have been studied in the 6-18 GHz frequency range using a molecular beam Fourier transform microwave spectrometer. Two different isomers have been observed for the 1   :   1 adduct. The most stable (1   :   1a) is stabilized by two @entity3884 bonds O-HO[double bond, length as m-dash]C and @entity29148 with water closing a ring with the peptide group. For the other conformer (1   :   1b), water is placed on the other side of the @entity6738 group stabilized by O-HO[double bond, length as m-dash]C and C-HO hydrogen bonds. In 2-azetidinone-(H2O)2 the water molecules close a ring with the peptide group forming three different @entity3884 bonds: O-HO[double bond, length as m-dash]C, O-HO and @entity29148 . The spectra of the parent and several isotopologues of each cluster have been investigated in order to determine their structures. The @entity3884 bond geometries show that the dominant interaction is the O-HO[double bond, length as m-dash]C hydrogen bond, in good agreement with the observed preference of water to interact with this group in proteins. A comparison between the geometries of the different observed adducts shows clearly how cooperative @entity3884 bonding plays an important role in the stabilization of these complexes. No detectable structural changes have been observed for @entity68570 upon hydration with one water molecule.

Microsolvation of XXXX : a model for the peptide group-water interactions.

@entity6738 :: ('CHEBI:23019', 'Chemical') :: ['carbonyl'] @entity68570 :: ('MESH:C116379', 'Chemical') :: ['2-Azetidinone', '2-azetidinone'] @entity3884 :: ('MESH:D006859', 'Chemical') :: ['hydrogen'] @entity29148 :: ('CHEBI:29772', 'Chemical') :: ['N-HO']
@entity68570 :: (MESH:C116379,Chemical) :: ['2-azetidinone']
