Synthesis and Crystal Structure of 2′-Se-Modified Guanosine Containing DNA

Selenium modification of nucleic acids is of great importance in X-ray crystal structure determination and functional study of nucleic acids. Herein, we describe a convenient synthesis of a new building block, the 2′-SeMe-modified guanosine (G_Se) phosphoramidite, and report the first incorporation of the 2′-Se-G moiety into DNA. The X-ray crystal structure of the 2′-Se-modified octamer DNA (5′-GTG_SeTACAC-3′) was determined at a resolution of 1.20 Å. We also found that the 2′-Se modification points to the minor groove and that the modified and native structures are virtually identical. Furthermore, we observed that the 2′-Se-G modification can significantly facilitate the crystal growth with respect to the corresponding native DNA.