Conformational studies of the (+)-trans, (-)-trans, (+)-cis, and (-)-cis adducts of anti-benzo[a]pyrene diolepoxide to N2-dG in duplex oligonucleotides using polyacrylamide gel electrophoresis and low-temperature fluorescence spectroscopy.
Using polyacrylamide gel electrophoresis (PAGE) and low-temperature, laser-induced fluorescence line narrowing (FLN) and non-line narrowing (NLN) spectroscopic methods, the conformational characteristics of stereochemically defined and site-specific adducts derived from the binding of 7 beta,8 alpha-dihydroxy-9 alpha,10 alpha-epoxy-7,8,9,10- tetrahydrobenzo[a]pyrene (anti-BPDE, a metabolite of the environmental carcinogen benzo[a]pyrene), to DNA were studied. The focus of these studies was on the four stereochemically distinct anti-BPDE modified duplexes 5'-d(CCATCGCTACC).(GGTAGCGATGG), where G denotes the lesion site derived from trans or cis addition of the exocyclic amino group of guanine to the C10 position of either (+) or (-)-anti-BPDE. PAGE experiments under non-denaturing conditions showed that the (+)-trans adduct causes a significantly greater retardation in the electrophoretic mobility than the other three adducts, probably the result of important adduct-induced distortions of the duplex structure. Low-temperature fluorescence studies in frozen aqueous buffer matrices showed that the (+)-trans adduct adopts primarily an external conformation with only minor interactions with the helix, but a smaller fraction (approximately 25%) appears to exists in a partially base-stacked conformation. The (-)-trans adduct exists almost exclusively (approximately 97%) in an external conformation. Both cis adducts were found to be intercalated; strong electron-phonon coupling observed in their FLN spectra provided additional evidence for significant pi-pi stacking interactions between the pyrenyl residues and the bases. FLN spectroscopy is shown to be suitable for distinguishing between trans and cis adducts, but lesions with either (+)- or (-)-trans, or (+)- or (-)-cis stereochemical characteristics showed very similar vibrational patterns.(ABSTRACT TRUNCATED AT 250 WORDS)
Suh
M
M
Ames Laboratory-USDOE, IA 50011, USA.
Ariese
F
F
Small
G J
GJ
Jankowiak
R
R
Liu
T M
TM
Geacintov
N E
NE
D001483:Base Sequence; D001564:Benzo(a)pyrene / Q000737:chemistry*; D001580:Benzopyrenes / Q000737:chemistry*; D055592:Biophysical Phenomena; D001703:Biophysics; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D018736:DNA Adducts / Q000737:chemistry*; D008968:Molecular Conformation; D008969:Molecular Sequence Data; D015394:Molecular Structure; D009841:Oligonucleotides / Q000737:chemistry; D013050:Spectrometry, Fluorescence; D013237:Stereoisomerism; D013696:Temperature
D001580:Benzopyrenes; D018736:DNA Adducts; D009841:Oligonucleotides; C056612:benzo(a)pyrene-DNA adduct; D001564:Benzo(a)pyrene; C072019:benzo(a)pyrene diolepoxide I