The T-1 relaxation rate of C2' at natural abundance of four different stereoselectively C2' deuterio-labelled nucleotide residues [2'-H-2 (S): similar to 85 atom% H-2, 2"-H-2 (R): similar to 15 atom% H-2: 3'- and 5'/5"-H-2: >97 atom% 2H; 4'-H-2: similar t