Use of C-13 tags with specifically N-15-labeled DNA and RNA

We describe methods to introduce C-13 specifically to the C2 or C8 position s of N-15-multilabeled purines, thereby permitting C-13 tagging" of all bas e nitrogens except the amino group of adenosine. These procedures permit th e incorporation of two or more N-15-multilabeled monomers into a given DNA or RNA fragment, with and without appropriate C-13 tags. This approach incr eases the number of N-15-nmr resonances that can be unambiguously distingui shed and thus the amount of information from a single synthesis and a singl e nmr experiment. (C) 1998 John Wiley & Sons, Inc.