EasySpin forum

I am trying to simulate the cw-EPR spectra of 2[4Fe-4S] cluster ferredoxin. The protein has two interacting S =1/2 iron sulfur clusters. The exp g values for the EPR spectra are 1.83, 1.89, 1.95, 2.01, 2.05 and 2.11. I am using the following script:

Sys1.S = 1/2;
Sys2.S = 1/2;
Sys1.g = [2.01 2.05 2.11];
Sys2.g = [1.83 1.89 1.95];
Sys1.lw = 3;
Sys2.lw = 3;
Vary1.lw = .5;
Vary2.lw = .5;
Vary1.g = [.05 0.05 .05];
Vary2.g = [.05 0.05 .05];
Exp.mwFreq = 9.7;
Exp.Range = [300 390]
Exp.Temperature = 15;
Exp.ModAmp = 1;
esfit('pepper',spc,{Sys1, Sys2},{Vary1, Vary2},Exp);

The simulated spectra does not fit the exp data very well. I wanted to know if I the script lacks any critical piece of information. Any input would be helpful.

Thanks
Karim

If the two clusters are coupled, you need to include both of them in the same spin system structure and add a coupling in Sys.ee. See the documentation on spin systems, which contains a section on electron-electron couplings.