ISSN:
0006-3525
Keywords:
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
DNA oligonucleotides with dA and dU residues can form duplexes with trans d(A · U) base pairing and the sugar-phosphate backbone in a parallel-stranded orientation, as previously established for oligonucleotides with d(A · T) base pairs. The properties of such parallel-stranded DNA (ps-DNA) 25-mer duplexes have been characterized by absorption (uv), CD, ir, and fluorescence spectroscopy, as well as by nuclease sensitivity. Comparisons were made with duplex molecules containing (a) dT in both strands, (b) dU in one strand and dT in the second, and (c) the same base combinations in reference antiparallel-stranded (aps) structures. Thermodynamic analysis revealed that total replacement of deoxythymine by deoxyuridine was accompanied by destabilization of the ps-helix (reduction in Tm by -13°C in 2 mM MgGl2, 10 mM Na-cacodylate). The U-containing ps-helix (U1 · U2) also melted 14°C lower than the corresponding aps-helix under the same ionic conditions; this difference was very close to that observed between ps and aps duplexes with d(A · T) base pairs. Force field minimized structures of the various ps and aps duplexes with either d(A · T) or d(A · U) base pairs ps/aps and dT/dU combinations are presented. The energy-minimized helical parameters did not differ significantly between the DNAs containing dT and dU. © 1996 John Wiley & Sons, Inc.
Additional Material:
11 Ill.
Type of Medium:
Electronic Resource
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