Stereochemical effects of non-ionic methylphosphonates on nucleotide conformations

Swarna Latha, Y. ; Yathindra, N. (1991) Stereochemical effects of non-ionic methylphosphonates on nucleotide conformations International Journal of Biological Macromolecules, 13 (5). pp. 301-306. ISSN 0141-8130

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The preferred conformations of deoxyribo and ribonucleoside 3'-methylphosphonates are analysed by minimizing the conformational energy as a function of all the major parameters including the sugar ring for both the S- and R-isomers. The results show that neither the substitution nor the nature of the diastereomer affects significantly the preferred conformations compared to the naturally occurring nucleoside 3'-phosphates. The preferred range of CImage '-03' bond torsions or the phase angles of pseudorotation (P) of the sugar are unaffected. The chiral substitution on the phosphate always adopts a conformation distal to the secondary C3' carbon atom in the minimum energy conformational state. Further, it introduces certain restrictions on the preferred range of P-03' torsions depending on the methylphosphonate configuration. Methylphosphonate, especially the S-isomer, renders the normal gauche- range of P-'03 bond torsions responsible for the stacked helical duplexes to be energetically unfavourable besides introducing a high energy barrier between trans and gauche conformations. Therefore it is suggested that duplexes with S-methylphosphonate may favour extended phosphodiester conformations. These factors explain the observed lower melting temperature as well as the downfield shifts in the 31P signals in duplexes containing the S-isomer.

Item Type:Article
Source:Copyright of this article belongs to Elsevier Science.
Keywords:Methylphosphonates; Stereochemistry; Nucleotides; Conformation
ID Code:58713
Deposited On:02 Sep 2011 03:48
Last Modified:02 Sep 2011 03:48

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