Abstract
Ribonucleic acids (RNAs) play a key role in many fundamental life processes. In living organisms, these polymers are often found complexed with proteins in extremely large ribonucleoprotein (RNP) assemblies whose molecular weight may reach several millions of Daltons (e.g., viruses, ribosomes, spliceosomes). For such inherently polymorphic assemblies, visualization by electron microscopy (EM) provides structural information at a resolution that is difficult to obtain in any other way (Chiu and Schmid, 1997; Griffith et al., 1997). Yet, localization and tracing by electron microscopy of RNA within RNP complexes of biological importance is not yet a straightforward undertaking. Here we describe a strategy for the synthesis of RNA molecules that are covalently derivatized with gold clusters, and thereby can be visualized by conventional transmission EM (TEM) or by atomic force microscopy (AFM). It is anticipated that when such an RNA molecule is incorporated into an RNP complex, it would be possible to localize and trace its fold by virtue of the gold clusters it contains.
