On-line identification of diastereomeric dibenzo[a,l]pyrene diol epoxide-derived deoxyadenosine adducts by capillary electrophoresis-fluorescence line-narrowing and non-line narrowing spectroscopy

A capillary electrophoretic method for the separation and on-line identific ation of closely related analytes using low-temperature fluorescence spectr oscopy is reported for the eight diastereomeric deoxyadenosine (dA) adducts derived from dibenzo[a,l]pyrene diol epoxide (DB[a,l]PDE). Electrophoretic separation of stereoisomers was accomplished by application of a mixed sur factant buffer [dioctyl sulfosuccinate (DOSS)and Brij-S], which was below t he critical micelle concentration (CMC) due to the high concentration (simi lar to 25%) of organic solvent. Addition of multiple surfactant additives t o the separation buffer provided electrophoretic resolution, which was unat tainable under single surfactant conditions. It is shown that the CE-separa ted analyte zones could be identified on-line via low-temperature (4.2 K) f luorescence non-line narrowing and fluorescence line-narrowing (FLN) spectr oscopy. In addition, it was determined that in CE buffer trans-syn-,cis-syn - and cis-anti-DB[a,l]PDE-14-N(6)dA diastereomeric adducts exist mostly wit h the -dA and DB[a,l]P moiety in an "open"-type conformation while the tran s-anti-DB[a,l]PDE-14-N6dA adducts exist in two different conformations whos e relative distribution depends on matrix composition. The above conformati ons have also been revealed by selective laser excitation. Thus, the low-te mperature methodology not only provides fingerprint structure via vibration ally resolved 4.2 K fluorescence spectra for adduct identification, but als o provides conformational information on the spatial relationship of the ca rcinogen and dA moiety. These results, taken together with those for DB[a,I ]P-DNA adducts formed in standard glasses and mouse epidermis exposed to DB [a,l]P, support our earlier findings that DB[a,l]P-derived adducts exist in different conformations [Jankowiak et al., Chem. Res. Toxicol. 11 (1998) 6 74]. Therefore, the combination of the separation power of CE and spectral selectivity of low-temperature fluorescence spectroscopy at NLN and FLN con ditions provides a powerful methodology which should prove useful for ident ification of closely related DNA adducts formed at low levels in biological systems. (C) 1999 Elsevier Science BN. All rights reserved.