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Figure 2.
Figure 2. the configurations of the oxygen (or sulfur)
atoms about the scissile phosphate of normal or phos-
phorothioate DNA. The phosphates are shown in the
orientation that will occur in all other Figures. (a) Nor-
mal, or all-oxygen phosphate. The pro-R and pro-S pos-
itions are marked. The negative charge is distributed
between the non-bridging oxygens. (b) Rp phosphor-
othioate phosphate. Note that the sulfur atom has only
a single covalent bond to the phosphorus atom and is
negatively charged. The pro-S oxygen features a double
bond to phosphorus. (c) The Sp phosphorothioate.
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