ISSN:
0006-3525
Keywords:
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
Methylation of phosphate groups in oligo-dT strands leads to a parallel duplex with T · T base pairs. Molecular mechanics calculations on parallel d(TTTTTT)2 show it to be a symmetric right-handed helix with B-DNA conformational characteristics. Phosphate methylation stabilizes the duplex by ca. 41 kcal/mol, due to removal of the interstrand phosphate electrostatic repulsions. The chirality introduced with phosphate methylation is important for the molecular geometry, since RP methylation predominantly influences the conformation around the ζ bond (P—O3′), while SP methylation mostly changes the α conformation (P—O5′). This is also true in antiparallel helices with methylated phosphates, as is shown by molecular mechanics calculations on d(GCGCGC)2. These results may be of relevance to protein-DNA interactions, where phosphate charges are also shielded. As the pro-SP oxygen is most available in a right-handed helix, we suggest changes around the α bond to occur upon protein complexation, leading to a widening of the major groove in the d(GCGCGC)2 duplex (from 12 to 13 Å) and reduced minor groove (from 6 to 5 Å).
Additional Material:
10 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/bip.360260902
Permalink
