Enzymatic synthesis of phosphoroselenoate DNA using thymidine 5'-(alpha-P-seleno)triphosphate and DNA polymerase for X-ray crystallography via MAD

Synthesis of Selenium-Derivatized Cytidine and Oligonucleotides for X-ray Crystallography Using MAD

Synthesis of the novel 2'-Se-cytidine phosphoramidite was achieved via transformation of the uridine analogue to the cytidine derivative in high yield. This 2'-Se-cytidine phosphoramidite was used to synthesize selenium-derivatized DNA and RNA oligonucleotides for X-ray crystallography using MAD. The nucleotide coupling yield using this novel phosphoramidite was over 99% when 5-benzylmercaptotetrazole (5-BMT) was used as the coupling reagent.

Selenium derivatization and crystallization of DNA and RNA oligonucleotides for X-ray crystallography using multiple anomalous dispersion

We report here the solid phase synthesis of RNA and DNA oligonucleotides containing the 2'-selenium functionality for X-ray crystallography using multiwavelength anomalous dispersion. We have synthesized the novel 2'-methylseleno cytidine phosphoramidite and improved the accessibility of the 2'-methylseleno uridine phosphoramidite for the synthesis of many selenium-derivatized DNAs and RNAs in large scales. The yields of coupling these Se-nucleoside phosphoramidites into DNA or RNA oligonucleotides were over 99% when 5-(benzylmercapto)-1H-tetrazole was used as the coupling reagent. The UV melting study of A-form dsDNAs indicated that the 2'-selenium derivatization had no effect on the stability of the duplexes with the 3'-endo sugar pucker. Thus, the stems of functional RNA molecules with the same 3'-endo sugar pucker appear to be the ideal sites for the selenium derivatization with 2'-Se-C and 2'-Se-U. Crystallization of the selenium-derivatized oligonucleotides is also reported here. The results demonstrate that this 2'-selenium functionality is suitable for RNA and A-form DNA derivatization in X-ray crystallography.