Fig. 3

Chlorophylls as interceptor molecules of environmental polycyclic aromatic hydrocarbons. a Interaction of CHL with benzo [a]pyrene-7,8-dihydrodiol-9,10-epoxide (BPDE). Absorption spectra for BPDE (dashed line), CHL (dotted line), and BPDE+CHL (solid line) in Tris-HCl buffer, pH 7.4, 20 °C. Inset: difference spectrum for the BPDE/CHL complex. b Time-dependent hydrolysis of BPDE in presence and absence of CHL. Upper panel: the hydrolysis of 10 μM BPDE to tetrols was recorded at 5-min intervals in Tris-HCl buffer, pH 7.4, 20 °C. Lower panel: repeat of the above experiment in the presence of 5 μM CHL. Numbers adjacent to spectra indicate the time in minutes at which each spectrum was recorded. The pseudo-first-order hydrolysis rate constant of BPDE to tetrols was 1.76 ± 0.67 in buffer and 8.37 ± 0.82 in buffer containing CHL (k_H (s^− 1) × 10³). c Energy minimized molecular model of the BPDE:CHL complex. Initial structures of CHL (top) and BPDE (bottom) were constructed using MM2 force field parameters and conjugate gradient methods. Complexes were obtained by first energy minimizing the structures of CHL and BPDE separately, then placing each molecule within Van der Waals radii and energy minimizing the corresponding complex. After multiple iterative docking experiments, complexes consistently had the epoxide oriented towards acid (carboxyl) groups or the methylene bridge in CHL, with minimization energies in the range − 16.9 to − 20.8 kcal/mol. Complexes were minimized to a gradient of 0.001 kcal/mol and calculations were performed using HyperChem (Release 2, Autodesk). d Natural Chla complexes with dibenzo [def,p] chrysene (DBC). e Chla and CHL lower the bioavailability of DBC and (inset) DBC-DNA adducts detected in trout liver (***P < 0.001). f Concentration-dependent inhibition of DBC-induced tumorigenesis in the rainbow trout. From published reports [15, 40,41,42]