G. Saint-Ruf

High-performance liquid and gas-liquid chromatography of isomeric phenoxathiins. Use of organo-clay to increase selectivity

SummaryBentone-34, a selective adsorbent, has been studied for use in high-performance liquid chromatography (HPLC) to separate isomeric phenoxathiin derivatives. We have compared the performance of this adsorbent in gas chromatography and liquid chromatography. We have obtained better and faster analyses of these isomeric phenoxathiins by high-pressure liquid-solid chromatography. This method is more flexible, as we have the choice of a large variety of mobile phases, and analyses are achieved at ambient temperature. Moreover HPLC can be used for collecting the pure solutes.

Hyperreactivity of the B-Z Junctions Probed by Two Aromatic Chemical Carcinogens, 2-N,N-Acetoxyacetylaminofluorene and 3-N,N-Acetoxyacetyl-Amino-4,6-Dimethyldipyrido[1,2-a:3′,2′-d] Imidazole

The reaction between DNAs in various conformations and two isosteric chemical carcinogens 2-N,N–cetoxyacetylaminofluorene and 3-N,N–cetoxya-cetylamino-4,6-dimethyldipyrido[1,2–:3′,2′-d] imidazole has been studied. The modification of DNA has been analysed at the nucleotide level by means of the 3′–5′ exonuclease activity of T4 DNA polymerase. Both carcinogens bind covalently to (dC-dG)16 and (dG-dT)15 sequences inserted in closed circular plasmids when the inserts are in the B form; they do not bind to these inserts when they are in the Z form. The reactivity of guanine residues at the B-Z junction depends upon the superhelical density of the plasmids and upon the base sequence at the junction. A strong hyperreactivity is observed on the 3′ side of the (dC-dG)16 in pLP32, the insert being in the Z form. It is concluded that the reactivity of guanine residues with both carcinogens depends upon the DNA conformation. The non-reactivity of Z-DNA and the hyperreactivity of some sequences under topological stress might have some importance in chemical carcinogenesis.