H. Li et al., BORON-CONTAINING OLIGODEOXYRIBONUCLEOTIDE 14MER DUPLEXES - ENZYMATIC-SYNTHESIS AND MELTING STUDIES, Nucleic acids research, 23(21), 1995, pp. 4495-4501
A set of three 14mer oligodeoxyribonucleotides of sequence d(5'-CTATGG
CCTCAGCT-3/3'-GATACCGGAGTCGA5') containing G* variants either as 2'-d
eoxyguanosine phosphate (unmodified), N7-cyanoborane 2'-deoxyguanosine
phosphate (base-modified) or 5'-deoxyguanosine boranophosphate (backb
one-modified) were synthesized by template-directed primer extension,
Both the N7-cyanoborane 5'-deoxyguanosine triphosphate and 2'-deoxygua
nosine alpha-boranotriphosphate nucleotides are good substrates for Se
quenase, We infer that a single S-p boranophosphate linkage (which has
a stereochemistry equivalent to the corresponding R(p) thiophosphate
analog) is formed in the backbone-modified 14mer, Thermally induced he
lix-coil transitions were monitored for the hybridized duplexes using
UV and circular dichroism (CD) spectroscopy, The CD spectra of the two
types of boron-modified hybrids closely resemble the unmodified paren
t duplex, forming B-type helices in 150 mM NaCl, 1 mM EDTA, 10 mM phos
phate, pH 7.4, buffer, UV melting results indicate that both hybrids h
ave stabilities comparable with the parent duplex as measured by T-m o
r Delta G degrees(25). These studies indicate that singly modified bas
e- or backbone-boronated DNA are good analogs of normal DNA.