Conformational transition of DNA in electroreduction studied by in situ UVand CD thin layer spectroelectrochemistry

Electrochemically induced three conformational transitions of calf thymus D NA from B-10.4 to Z(10.2)-DNA and from B-10.2 to B-10.4 and to C-DNA in 10 mM phosphate buffer solution (pH 7.21) at glassy carbon electrode are found and studied by in situ circular dichroism (CD) thin layer spectroelectroch emistry with singular value decomposition least square (SVDLS) analysis. It indicates that the so-called B-10.2 form and the C-form of DNA may be comp osed of B-10.4 and left-A DNA and of B-10.4 and right-A DNA, respectively. The irreversible electrochemical reduction of adenine and cytosine groups i n the DNA molecule is studied by UV-Vis spectroelectrochemistry. Some elect rochemical parameters alphan = 0.17, E-0' = -0.70 V (vs. Ag/AgCl), and the standard heterogeneous electron transfer rate constant, k(0) = 1.8 x 10(-5) cm s(-1) are obtained by double logarithmic analysis and non-linear regres sion. (C) 2000 Elsevier Science B.V. All rights reserved.