We have studied the inner-sphere reorganization energy and interaction of the it orbitals in DNA. We predict an increase of the intrastrand electronic coupling in the oligomers with the increase of the number of base pairs due to the lattice packing effect. We estimate the geometry relaxation of the base pairs within the (A-T), and (G-C), oligomers (n = 1-6) due to their oxidation. A decrease of the inner-sphere reorganization energy with increasing n was observed. The maximum degree of geometry relaxation is found to be located close to the oligomer center for n <= 4. (C) 2007 Elsevier B.V. All rights reserved.