Phosphorus 31 solid state NMR characterization of oligonucleotides covalently bound to a solid support.

31P cross polarization (CP) magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectra were acquired for various linear and branched di- and tri-nucleotides attached to a controlled pore glass (CPG) solid support. The technique readily distinguishes the oxidation state of the phosphorus atom (phosphate versus phosphate), the presence or absence of a protecting group attached directly to phosphorus (cyanoethyl), and other large changes in the phosphorus chemistry (phosphate versus phosphorothioate). However, differences in configurational details remote from the phosphorus atom, such as the attachment position of the ribose sugar (2'5' versus 3'5'), or the particulars of the nucleotide bases (adenine versus uridine versus thymine), could not be resolved. When different stages of the oligonucleotide synthetic cycle were examined, 31P CPMAS NMR revealed that the cyanoethyl protecting group is removed during the course of chain assembly.