A circular dichroism study on the conformation of d(CGT) modified with N-acetyl-2-aminofluorene or 2-aminofluorene.
The trinucleotide d(CGT) was modified by covalent binding of the carcinogen N-acetyl-2-aminofluorene (AAF) or 2-aminofluorene (AF) at the C8 position of the guanine base. The conformations of d(CGT)-AAF and -AF were studied by comparing the absorption and circular dichroism properties with those of dCMP + dGMP-AAF or -AF + dTMP in a molar ratio of 1:1:1 and AAF- and AF-containing dGMP. For both AAF- and AF-d(CGT) complexes the results show significant stacking interactions between the fluorene residue and the base(s) and are discussed in terms of the conformation of d(CGT)-AAF and -AF. In d(CGT)-AF we observe a clear interaction between AF and thymine, whereas the C-G stack is still intact. In the case of d(CGT)-AAF the C-G stack is weakened and the glycosidic rotation angle of dGuo-C8-AAF is most probably syn. The specific fluorene-base interactions persist at elevated temperatures. The carcinogen-base interactions are stronger in the AAF-carrying d(CGT) than in the case of the deacetylated complex. This is consistent with the higher mobility of the AF-adduct and its conformationally heterogeneous appearance in DNA.
van Houte
L P
LP
Free University, Department of Biophysics, Amsterdam, The Netherlands.
Westra
J G
JG
Retèl
J
J
van Grondelle
R
R
D015073:2-Acetylaminofluorene / Q000737:chemistry*; D002273:Carcinogens / Q000737:chemistry*; D002942:Circular Dichroism; D005449:Fluorenes / Q000737:chemistry*; D008958:Models, Molecular; D009690:Nucleic Acid Conformation; D009838:Oligodeoxyribonucleotides / Q000737:chemistry*; D013053:Spectrophotometry; D013696:Temperature
D002273:Carcinogens; D005449:Fluorenes; D009838:Oligodeoxyribonucleotides; C012177:2-aminofluorene; C072760:deoxy(cytidylyl-guanylyl-thymidylic acid); D015073:2-Acetylaminofluorene