Analysis of temperature dependence of the 1H and 13C isotropic shifts of horse heart ferricytochrome c: explanation of Curie and anti-Curie temperature dependence and nonlinear pseudocontact shifts in a common two-level framework

Research was conducted to elucidate the anomalous properties exhibited by hyperfine shifts of carbon nuclei and protons of methyls of the heme of cytochrome c. The results provided strong evidence that the two methyl protons have anti-Curie temperature dependence. This was attributed to the opposite sign of the contact shift for the two nuclei and the metal-centered pseudocontact shifts for carbons. The findings were also consistent with theoretical predictions.