engleski

EPR study of copper complexes with nucleic-acid basis

EPR spectroscopy was used to study the complex formed in crystals of 5-methyl-2-thiouracil (2-thiothymine) containing traces of copper. The copper impurities, originally present as Cu(I)-complex of 2-thiothymine in the lattice of 2-thiothymine, are transformed into paramagnetic Cu(II)-complex by ionizing radiation. It was found that the complex is planar, the plane being defined by two pairs of S and N atoms, from two adjacent 2-thiothymine molecules. The structure of the complex suggests that a pair of hydrogen bonds between two neighboring molecules is replaced by a stronger Cu-coordination bonding, with two sulfur and two nitrogen atoms as ligands. The spectroscopic parameters (g-tensor, A(63Cu) and A(14N) tensors) are essentially similar to those earlier observed for copper planar centers in other systems. © 2004 Elsevier B.V. All rights reserved.

EPR spectroscopy; free radicals; copper

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