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4-, 5- and 6-Nitroindole have been investigated and compared with 3-nitropyrrole as universal bases in oligodeoxynucleotides. Of these the 5-nitroindole derivative was found to be superior giving higher duplex stability, and behaving indiscriminately towards each of the four natural bases in duplex melting experiments. 3-Nitropyrrole, whilst not discriminating between the natural bases, was found to lead to considerable destabilisation of the duplexes, particularly when multiple substitutions were made, in contrast to the 5-nitroindole nucleoside.

1965]Phosphate Esters : Efect of Changing Ester Grot@ 6559 and not to any peculiarity of the cyclohexyl ester as such. This general view has been confirmed by an investigation of the rates of hydrolysis of a series of esters of 2-hydroxypropyl phosphate (I). The esters were prepared by reaction between the alkyl or aryl phosphate and 1,2-epoxypropane in aqueous solution at about pH 8. The rates and product CHzO 0 -* The first-order rate constant for hydrolysis of barium propane-1,2-diol cyclic phosphate in 0 . 1~-NaOH a t 30" can be calculated as very roughly 3 x sec.-l from the data of T. Ukita, K. Nazasawa, and M. Irie. Pharm. Bull. (Tokyo), 1957, 5, 127. t The equation of the line for alkaline hydrolysis of the acetates is log koH = -0.26 pK, + 5-0 (cf. ref. 5 ) .D.

No abstract

3-Nitropyrrole and 5-nitroindole have been assessed as universal bases in primers for dideoxy DNA sequencing and in the polymerase chain reaction (PCR). In contrast to a previous report, we have found that the introduction of more than one 3-nitropyrrole residue at dispersed positions into primers significantly reduced their efficiency in PCR and sequencing reactions. Primers containing 5-nitroindole at multiple dispersed positions were similarly affected; for both bases only a small number of substitutions were tolerated. In PCR experiments neither base, when incorporated into primers in codon third positions, was as effective as hypoxanthine, which was incorporated in six codon third positions in a 20mer oligomer. However, primers containing up to four consecutive 5-nitroindole substitutions performed well in both PCR and sequencing reactions. Consecutive 3-nitropyrrole substitutions were tolerated, but less well in comparable reactions.

No abstract

Exposure of DNA to methylene blue and visible or ultraviolet light causes guanine-specific modification, and subsequent treatment with piperidine leads to chain cleavage at each guanine residue. Treatment of DNA with osmium tetraoxide in dilute pyridine leads to thymidine-specific modification, and subsequent treatment with piperidine leads to chain cleavage at the modified thymidine residues. Both reactions can be used in conjunction with other base specific modifications described by Maxam and Gilbert (1) for the determination of the nucleotide sequence in DNA.

No abstract