Se. Osborne et al., DESIGN, SYNTHESIS, AND ANALYSIS OF DISULFIDE CROSS-LINKED DNA DUPLEXES, Journal of the American Chemical Society, 118(48), 1996, pp. 11993-12003
The design, synthesis, and analysis of analogs of d(CGCGAATTCGCG)(2) p
ossessing one or two intrahelical disulfide cross-links is reported. T
he cross-linked oligomers were prepared by first synthesizing duplexes
where the 3'- and 5'-terminal bases of the parent sequence were repla
ced with N-3-thioethylthymidine. Following deprotection and purificati
on, air oxidation afforded the desired cross-linked constructs in high
yield. Analysis of both the oxidized (disulfide cross-linked) and red
uced (thiol modified) duplexes by UV, circular dichroism, and NMR spec
troscopies along with susceptibility to EcoRI cleavage indicates that
the modifications are not structurally perturbing. Optical thermal den
aturation and differential scanning calorimetry measurements suggest t
hat introducing disulfide cross-link(s) into d(CGCGAATTCGCG)(2) does,
however, cause two fundamental changes. First, the cross-link(s) incre
ase the thermal stability of the modified duplexes by changing the mol
ecularity of denaturation without an increase in enthalpy. Second, the
disulfide cross-link traps one of the conformations of the conformati
onally heterogeneous parent molecule resulting in a conformationally h
omogeneous system. Both of these features are themselves unique and wi
ll be important for further applications of disulfide cross-linked oli
gomers such as these in studies of nucleic acid structure and function
.