SPATIAL STRUCTURES OF 3'-ESTRONE AND 5'-E STRONE ESTERS OF TETRANUCLEOTIDE REFINED BY 2-DIMENSIONAL NMR-SPECTROSCOPY AND RESTRAINED MOLECULAR MODELING

The spatial structure of a tetranucleotide with an estrone residue cov alently linked to the 3'-terminal phosphate [pd(CAGC)p-EsS] or 5'-term inal phosphate [EsS-pd(CAGC)] was studied by one and two-dimensional H -1, C-13, and P-31 NMR spectroscopy. The proton resonances were assign ed by using NOESY, ROESY, COSY, and C-13, H-1-correlation spectra. The proton resonances in the H-1 NMR spectrum at room temperature for the 3'-estrone derivative of the tetranucleotide were significantly broad ened compared with its mononucleotide analog pdCp-EsS. A probable stru cture of this molecule that best fit the experimental set of interprot on distances and torsion angles was simulated using the restrained mol ecular mechanics. The results suggest a considerable interaction betwe en the 3'-estrone residue and the oligonucleotide chain.