| Abstrakt: |
The X-band EPR spectra of Cu(cal)2 complex in CHCl3 solutions (cal = calcimycin) do not show resolved 14N hyperfine structure (J. S. Puskin and T. E. Gunter, Biochemistry 14, 187, 1975) even though they are expected from the nitrogen coordination to divalent metal ions inferred by NMR acid by model building (C. M. Deber and D. R. Pfeiffer, Biochemistry 15, 132, 1976). In the present work, unresolved hyperfine structure from two equivalent 14N has been inferred in the EPR spectra of Cu(cal)2 from an analysis of linewidths and lineshapes of mI = 32 and ½ transitions at 298 K and mI = 32 transition at 253 K, in CHCl3 solutions (mI = nuclear magnetic quantum number associated with the Cu hyperfine transition); g(parallel to); g|| − g⊥(=0.24), |A|| − A⊥| (=131 G), and 14N hyperfine constant AN (~11.3 G) determined from liquid solution linewidth studies in this work favor a solution structure of the complex in which two nitrogens and two oxygens are involved in the square-planar coordination at the metal ion similar to that suggested on the basis of the model for Ca(cal)2 complex.Copyright 1994, 1999 Academic Press, Inc. |
