Nucleic acids carbonyl oxygens

The number of possible forms is reduced somewhat by the fact that one of the nitrogens is bonded to the sugar in the nucleic acid it no longer carries a hydrogen to participate in tautomerism. The tautomeric forms indicated are found to predominate in nucleic acids. The oxygen substituents exist almost entirely as carbonyl groups, whereas... 

Hydrogen-bonding interactions are considerably weaker than ionic interactions and covalent bonds but have a profound effect on many chemical and physical properties [221] and determine the shapes of large molecules such as proteins and nucleic acids. Protein secondary structure is determined by H bonding between the carbonyl oxygen of one amide unit and the N—H bond of another. The two strands of the double helix of... 

Helically ordered chain structures are not limited to molecules containing a carbon-carbon backbone structure. They also manifest themselves in polypeptides, proteins, and nucleic acids. A very important ordered structure of polypeptides is the alpha-helix deduced by Pauling, Corey, and Branson.(26) In this structure (as contrasted with the extended ordered configuration of a polypeptide chain) the maximum number of hydrogen bonds between the carbonyl oxygen and amino... 

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