Synopsis: A tale of two nucleic acids

Subtle differences in how RNA and DNA behave in solutions may lead to better therapies.
Synopsis figure
Credit: N. J. Reiter, L. J. Maher III, and S. E. Butcher, Nucl. Acids Res. 36, 1227 (2008)
Image is Figure 6c from http://nar.oxfordjournals.org/content/36/4/1227.full. The article was published under CC (“unrestricted non-commercial use, distribution, and reproduction in any medium”) license. Please cite appropriately.

The information-bearing biological molecules, DNA and RNA, both coil into negatively charged double helices when complimentary strands pair up. But under conditions where positive ions from the surroundings allow double-stranded DNA to condense from solution, double-stranded RNA stays dissolved. The difference illustrates the subtlety of the biologically significant interactions between these molecules.

The messenger RNA that transfers genetic information from DNA into protein sequence consists of a single strand. But in other biological roles, RNA forms paired chains with complementary sequences, like its DNA cousin. The slightly different chemical backbone of RNA leads to a different double-helix structure, however. Using small-angle x-ray scattering, Li Li and colleagues from Cornell University had previously found that this structure allows triply charged positive ions to screen the negative charge more efficiently in RNA than in DNA. But in Physical Review Letters, the group reports that even though double-stranded RNAs associate more readily, they remain in solution in conditions where double-stranded DNA condenses. The researchers find that two rather different models of how the molecules and ions nest together can make sense of this surprising observation.

Clarifying how the detailed interactions sometimes lead to condensation should help biologists to characterize the many biological functions of RNA, and could also help researchers devise better ways to deliver double-stranded RNA to cells for therapy. – Don Monroe


Announcements

More Announcements »

Subject Areas

Biological Physics

Previous Synopsis

Atomic and Molecular Physics

Clocking the last century

Read More »

Next Synopsis

Interdisciplinary Physics

Cathedral’s invisible earthquake damage

Read More »

Related Articles

Synopsis: Maintaining the Sequence
Biological Physics

Synopsis: Maintaining the Sequence

Theoretical calculations indicate that an electrospray-based technique could correctly read out the amino acid sequence of protein molecules. Read More »

Synopsis: Neutron Stars in a Petri Dish
Nuclear Physics

Synopsis: Neutron Stars in a Petri Dish

Simulations of the dense matter in a neutron star’s crust predict the formation of structures that resemble those found in biological membranes. Read More »

Focus: Evolution Thins Out Distracting DNA
Biological Physics

Focus: Evolution Thins Out Distracting DNA

Proteins sometimes bind to the wrong stretch of DNA, but these "imposter" DNA sequences are statistically rare in many genomes, suggesting that evolution works against them. Read More »

More Articles