Dear EasySpin Community,
I hope this message finds you well. I am currently working on reproducing an X-band CW-EPR spectrum of T. elongatus in the S2 state, as shown in the attached figure (Fig. S1). I would greatly appreciate any guidance on how to achieve this simulation using EasySpin.
Experimental Details:
Sample Treatments: The X-band CW-EPR measurements were performed to assess protocols for ammonia addition and Ca²⁺/Sr²⁺ exchange.
Both treatments modify the S2 state EPR spectrum, which is a structured 𝑆=1/2 signal, 200 mT wide at X-band, centered at g=2.
S2 State Preparation: The S2 state was prepared by continuous wave (CW) 200 K illumination. Afterward, samples treated with ammonia were
annealed in the dark at -10°C for 30 s to allow NH₃ to bind to the cofactor.
Spectral Changes: The EPR spectrum of the ammonia-bound (S2NH₃) and Mn₄O₅Sr cofactor both showed characteristic changes in line positions
and intensities compared to the wild-type (S2Ca). The changes in the S2 multiline spectrum have been previously interpreted as small
modifications of the electronic structure of the cofactor.
Data Subtraction: To isolate the clean cofactor spectrum in the S3 state, data from the dark S1 state spectrum were subtracted from the
spectrum recorded after two light flashes. This subtraction method eliminates the oxidized cytochrome (FeIII) signals from the PsbV subunit
and cytb559, which are present in the S1 state.
Key Experimental Parameters:
Microwave frequency: 9.6265 GHz (control), 9.6375 GHz (NH₃-treated), 9.6367 GHz (Ca²⁺/Sr²⁺ exchange)
Microwave power: 6.3 mW
Modulation amplitude: 7 G
Sweep time: 336 s
Time constant: 164 ms
Temperature: 10 K (NH₃), 8 K (Sr and control)
In all samples, the YD° signal centered at 𝑔≈2 was removed for clarity. I am using EasySpin to simulate similar EPR spectra, but I am facing challenges in replicating the exact line positions, intensities, and spectral features, particularly the modifications observed in the S2 state after ammonia treatment and Ca²⁺/Sr²⁺ exchange.
Would anyone be able to provide insights or a sample code to help reproduce this type of CW-EPR spectrum using EasySpin? Any help or suggestions would be greatly appreciated.
Thank you very much for your time and consideration.
Best regards,
Nie