PARTIALLY-DEUTERATED OLIGO-DNA REDUCES OVERCROWDING, ENHANCES RESOLUTION AND SENSITIVITY AND PROVIDE IMPROVED NMR CONSTRAINTS FOR STRUCTUREELUCIDATION OF OLIGO-DNA

The usefulness of the ''NMR-window III'' approach (see ref. 2e) has be en demonstrated through the use of the deuterio isotopomeric 12mer oli go-DNA duplex obtained from protected partially deuterated 2'((R) unde r bar/(S) under bar), 3', 5'((R) under bar/(S) under bar)-H-2(3)-2'-de oxyribonucleoside blocks [see preceding paper). The 2D-NMR spectra of this deuterio isotopomeric DNA duplex I were compared with those of th e natural counterpart (duplex II) and deuterium-labelled 12mer duplex III (prepared earlier by the ''NMR-window II'' approach, ref. 2e), and the results can be summarised as follows: (i) The simplification of t he crosspeak pattern in H1'-H2'/2 '' and H4'-H5'/5 '' areas in the DQF -COSY spectra reduces the spectral crowding, thereby allowing a precis e extraction of the coupling constants. (ii) The deuterio isotopomeric mixture of DNA duplex I provide hitherto unavailable nOe data sets wh ich are sensitive to the conformational changes of the sugar moiety or the backbone. (iii) The extractable number of nOe constraints based o n fully resolved crosspeaks and free from spin diffusion for deuterio isotopomeric dodecamer I are 308, whereas they are only 188 for the na tural counterpart, suggesting the usefulness of the nOe crosspeaks in the semi-quantitative approach for the NMR-constrained structure refin ement. (C) 1998 Elsevier Science Ltd. All rights reserved.