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Forces stabilizing Nucleic Acid Structures

Forces stabilizing Nucleic Acid Structures Sugar –Phosphate chain: Reasonably strain free. Conformationally relaxed arrangement of sugar phosphate backbone in double helices. Glycosidic bonds: syn or anti conformations. Mostly anti-conformation

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Forces stabilizing Nucleic Acid Structures

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  1. Forces stabilizing Nucleic Acid Structures Sugar –Phosphate chain: Reasonably strain free. Conformationally relaxed arrangement of sugar phosphate backbone in double helices. Glycosidic bonds: syn or anti conformations. Mostly anti-conformation Sugar Ring: C2’ endo conformation in B-DNA and C3’ endo in some RNA structures.

  2. Base Pairing: Standard Watson Crick base Pairind is most preferred. Other kind of pairings do occur in certain DNA and RNA structures. Watson Crick Base pairs are most stable as demonstrated by Lord and Rich by IR spectroscopy. IR spectrum of N-H bond. But H-bonds do not stabilize DNA structure: DNA is denatured in non-polar solvents (ethanol) which generally stabilize the H-bonding.

  3. Base Stacking and hydrophobic interactions: The major force involved in the stabilization of nucleic acid structures. Nucleic acid bases stack in aqueous solution The aggregation of bases can be monitored by measuring their osmotic coefficient (a colligative property) Destabilization of stacking by heating leads to hyperchomism (increase in the absorbance). The unstaking of the single stranded poly A by heat is a non-cooperative conformational change The stacking is very specific to the bases and the hydrophobic interactions responsible for this interaction is poorly understood

  4. Ionic interaction Stabilization of phosphate groups by cations. Divalent cations like Mg 2+ play significant role in stabilizing the nuclein acis structures.

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