Mixed oligomers, representing oligonucleotides connected with long non-nucleotide spacers, have been synthesized using phosphoramidite chemistry. The oligonucleotide moieties of the mixed oligomers fully or partially correspond in the structure to the consensus elements of -35 (TTGACA) and -10 (TATAATG) regions of prokaryotic promoters. The non-nucleotide spacers, approximating in size 17-membered DNA fragments, were synthesized using phosphoramidite derivatives of polyethylene glycol (PEG600), tetraethylene glycol or dodecanediol. It is shown that the oligonucleotide moieties of the mixed oligomers can form \"normal\" DNA like antiparallel complementary complexes, being the substrates of T4 DNA ligase. To obtain the DNA-like polymers with alternating natural and non-natural regions or cyclic structures, the enzymatic ligation of different complexes of the oligomers synthesized was studied.

A series of E. coli promoters made of the consensus -35 and -10 hexamers separated by 17 bp spacer with variously located bending dTn.dAn, n = 5 or 6, sequences was constructed and cloned into the plasmid pDS3. Electrophoretic gel mobilities of restriction fragments containing these promoters correlated with the number of the T tracts encoded in the promoter sequences. The open complexes formed by E. coli RNA polymerase on promoters containing the T5(-34...-38) tract exhibited gel retardation indicative of their different gross geometry. The strength of these promoters measured in vivo in relation to an internal transcriptional standard was shown to be significantly lower than that of the group without the T5(-34...-38) tract. Within both these groups the promoters with two T6 tracts in the spacer, aligned in phase with the B-DNA helix repeat, had lower transcriptional activity, while the T6 tract encoded in the -7...-2 promoter region apparently had no influence on the strength of the respective promoters.