DNA-RNA hybrids versus DNA-DNA hybrids

Mary Coventry coventry at chem.washington.edu
Tue Nov 21 00:49:43 EST 1995

In article <michet-0911951916470001 at mac-llx.biocell.fundp.ac.be>,
michet at biocell.fundp.ac.be (Christine HANS) wrote:

> HI ! it's Christina la BOMBA
> Would you please give us some informations about nucleic acid hybrids :
> - Why are DNA-RNA hybrids more stable than DNA-DNA hybrids (same length,
> same composition) ? We need some references.
> - What is the effect of bivalent cations on melting temperature and why do
> bivalent cations have more influence on Tm than monovalent cations ?
> -- 
> Christine HANS
> Laboratory of Cellular Biochemistry,
> Facultes Universitaires ND de la Paix,
> 61, rue de Bruxelles,
> B-5000 Namur (Belgium).
> Fax: ++/32/81/72.41.35.
> Email: michet at biocell.fundp.ac.be

Actually, RNA:DNA hybrids may be less stable than DNA duplexes. It is
very sequence-dependent (Biochemistry, 1995,34, 10807-10815 and ref. wherein).
The presence of 2'-OH group in RNA strand apparantly decreases the entropy 
loss upon duplex formation compare to DNA duplexes and makes hybrids
relativly more stable. At the same time, conformation of  DNA strand in
hybrids differs from "optimal" B-form geometry (Biochem.,
1993,32,4207-4215, J.Mol.Biol.,
1993, 233, 509-523). It can makes some hybrids less stable.

Sincerely, Oleg Fedoroff
Email: fedorov at mary.chem.washington.edu

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