ISSN:
0006-3525
Keywords:
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
The NaCl-induced transition from B to Z conformation in poly (dG-dC), covalently modified with benzo(a)pyrene diol epoxides (BPDE), has been studied by use of flow linear dichroism (LD), CD, and fluorescence spectroscopy. In contrast to unmodified poly (dG-dC), the BPDE-modified polynucleotide displays a B to Z conversion that is incomplete in 2.7 M NaCl. This and a number of other observations are found consistent with a locally retained BPDE perturbed B-like conformation in the vicinity of the BPDE adduct. In 2.7 M NaCl the polynucleotide orientation in flow is strongly reduced, which could indicate flexibility at the junctions between domains of BPDE perturbed B-like conformation and Z conformation. A virtually stable high-salt B form is found in 2.25 M NaCl at 0°C; its CD spectrum resembles that of the transient so-called B* form, which is observed at an early stage of the B to Z transition. Characteristic B to Z transition times were evaluated by taking this B*-form CD spectrum as the initial state spectrum. The kinetics of the B to Z transition, monitored by the CD signal at 287 nm, shows an increased transition rate with (+)-anti-BPDE modification whereas the (-)-anti- and (±)-syn-BPDE adducts have retarding effects. The difference is discussed against the background of the different binding geometries of the BPDE isomer adducts.
Additional Material:
8 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/bip.360290815
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