Under relatively mild conditions, nucleic acids and their constituents were trinitrophenylated with 2,4,6-trinitrobenzenesulfonate (TNBS) in aqueous solution (pH 8-11), yielding reddish-orange trinitrophenyl (TNP) derivatives. Guanine residues were trinitrophenylated on the base residues at the 2-amino group (N2-TNP derivatives), and in addition, 2'- and 3'-hydroxyl groups of the ribose moieties of nucleosides or nucleotides were trinitrophenylated to form Meisenheimer complexes. 2. The preparation of TNP derivatives (N2-TNP-guanine, -guanosine, N2, O-bis-TNP-guanosine, O-TNP-guanosine, -adenosine, -cytidine , and -uridine), their rates of formation, absorption spectra (UV, visible, and infrared), molar extinction coefficients, Rf value, electrophoretic mobilities, and stability in acid or alkaline solution, are presented. 3. Trinitrophenylation of several kinds of nucleic acid was investigated. Calf thymus DNA and yeast transfer RNA showed a resistance to trinitrophenylation compared to guanosine 3'(2')-phosphate, yeast RNA or denatured calf thymus DNA. TNP-RNA showed resistance to the action of ribonucleases T1 and T2 [EC 3.1.4.8 and 3.1.4.23]. 4. Trinitrophenylation reactions using 2,4,6-trinitrochlorobenzene and 2,4,6-trinitrofluorobenzene were compared with that using TNBS as regards specificity and reaction rate.
