Conformational transmission in 5'-P(IV) and 5'-P(V) TBP phosphorylated nucleosides : implications for DNA structure and dynamics

Specific conformational changes in DNA and RNA can be induced via a transient pentacoordination of the phosphorus atoms in the helix backbone. The details of this conformational transmission mechanism are discussed briefly, using experimental data that were obtained with a set of 5'-pIV and 5'-pV phosphorylated tetrahydrofurfuryl systems. A conformational study on the more realistic model system, the dinucleotide 2 in which a stabilized pentacoordinated phosphorus forms the internucleoside linkage, is presented. Furthermore, it has been found that methylation of the phosphate groups in d(TpTpTpTpTpT) results in the formation of a non-Watson & Crick type parallel duplex DNA structure, in which the two strands are joined via hydrogen bonding between the thymidine bases. Various physico-chemical techniques (e.g. NMR methods and UV hyperchromicity) were used to elucidate the structural details of the parallel duplex. Characteristic properties (parallellity, slimness, symmetry) are presented.