Nucleotide sequence of nuclear 5.7S RNA of mouse cells

Viable tumor cells were examined by ¹⁹F-NMR spectroscopy after treatment with 4-trifluoromethyl 2,6-dinitrophenyl sulphonate (CF₃-DNBS), which is an analog of 2,4,6-trinitrophenyl sulphonate (TNBS). The presence of a strong ¹⁹F-NMR signal from treated cells suggested the binding of the “probe”. Treatment of labelled cells with proteolytic enzymes significantly decreased the signals, suggesting that the label was essentially bound to the cell surface macromolecules. A proportion of the material bound to the cell was removable by dialysis of cell extracts against a structural analog, suggesting that some CF₃-DNBS-cell membrane bonds were not covalent. The existence of such non-covalent bonds has also been confirmed with soluble proteins. By the same approach, it was also found that ¹⁴C-TNBS formed covalent and non-covalent bonds with tumor cells.