PHOTOCROSS-LINKING OF NUCLEIC-ACIDS TO ASSOCIATED PROTEINS

Photocross-linking is a useful technique for the partial definition of the nucleic acid-protein interface of nucleoprotein complexes. It can be accomplished by one or two photon excitations of wild-type nucleop rotein complexes or by one photon excitation of nucleoprotein complexe s bearing one or more substitutions with photoreactive chromophores. C hromophores that have been incorporated into nucleic acids for this pu rpose include aryl azides, 5-azidouracil, 8-azidoadenine, 8-azidoguani ne, 4-thiouracil, 5-bromouracil, 5-iodouracil, and 5-iodocytosine. The various techniques and chromophores are described and compared, with attention to the photochemical mechanism.