Oooc oc

The molecular structures of the four RNA bases. Adapted from Robinson, 2001.

thermodynamics process of energy transfers during reactions, or the study of these processes enzymes proteins that control a reaction in a cell template a master copy

BASES

The bases are nitrogen-containing ring compounds, either purines or pyrimidines.

HC C

uracil

adenine

HC N

cytosine

guanine and transfer RNA (tRNA), have structures that are very complex. In structure they resemble proteins more than they do DNA.

To understand the function of a given RNA molecule, scientists often need to know its structure. There are three general strategies for analyzing RNA structure. First, using the relatively simple base-pairing rules for RNA and the basic principles of thermodynamics, computers can be used to predict secondary RNA structure, although not always with complete success.

Second, researchers can analyze RNA molecules from various organisms and compare those molecules that have the same function. Even when the nucleotide sequences vary between species, important structures are usually preserved.

Third, the structure of an RNA molecule can be determined experimentally, using enzymes to cut it or chemicals to modify it. Some enzymes and chemicals cut or modify only nonpaired, single-stranded portions of the RNA molecule, allowing researchers to identify double-stranded regions by examining which ones remain uncut and unmodified.

Despite the usefulness of each of these methods, none can provide a complete and accurate three-dimensional structure. A more complete determination of structure can be achieved by the biophysical methods of X-ray crystallography and nuclear magnetic resonance.

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