We wish to suggest a structure for the salt of deoxyribose nucleic acid (DNA). This structure has novel features that are of considerable biological interest in that it suggests a copying mechanism for genetic material.
Several structures for DNA have been suggested, but all are unsatisfactory in our opinion. Our structure uses molecular architecture similar to Fraser’s model, proposing that phosphates occupy the outer extremities of the chain, with the bases making up the central region. We propose that DNA consist of two helical chains each coiled around a central axis. Both chains follow right-handed helices, however, their orientations are anti-parallel. Each chain is composed of a phosphate-deoxyribose backbone, with 3’-5’ linkages.
Four molecules make up the structure of DNA, two pyprimidines, cytosine and thymine; and two purines, adenine and guanine. For bonding to occur, specific purines must join by hydrogen bonding with specific pyrimidines: adenine to thymine and cytosine to guanine, respectively. Bonding specificity is consequence of the molecules taking keto-configuaration. Our model is experimentally supported by reports claiming that ratios of adenine to thymine, and cytosine and guanine are always close to unity in DNA.
This model is biologically significant because it proposes that phosphates are readily available to be accessed by the cell’s excess of cations. Our model also assumes that DNA is an open, hydrophilic molecule, thus, highly water-soluble. Alternatively, at lower water content, DNA’s thermodynamic favorability is predicted to tilt its bases so that the structure can become more compact.
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