“…Gorelic (1975aGorelic ( ,b, 1976aGorelic ( ,b, 1977 has discussed, in detail, this factor and a number of other factors that must be properly evaluated before solid conclusions can be drawn about interactions of particular proteins with rRNA from photochemical cross-linking studies. Furthermore, account must be taken of such additional complexities as the occurrence of RNA and protein chain breakage (Gorelic, 1976c, Gorelic andParker, 1978), amino acid modification, and formation of nonadduct base photoproducts; all of these reactions could cause conformational changes and introduce difficulties in assessing the meaning of photochemical cross-linking experiments in intact ribosomes. It appears that the complete elucidation of the photochemistry of the intact E. coli ribosome and its subunits, over the fluence range of UV radiation required to cross-link most of the ribosomal proteins to rRNA, will be a challenging task.…”