General and efficient simulation of pulse EPR spectra

Abstract

We present a rather general and efficient method of simulating electron-spin echo spectra for spin systems where the microwave frequency does not simultaneously excite EPR transitions that share a common level. The approach can handle arbitrary pulse sequences with microwave pulses of arbitrary length and strength. The signal is computed as a sum over signals from the electron coherence transfer pathways contributing to the detected echo. For each pathway, amplitudes and frequencies of the signal components are computed and used to construct a spectral histogram from which the time-domain signal is obtained. For multinuclear spin systems, the nuclear subspace is factorized to accelerate the computation. The method is also applicable to high electron spin systems with significant zero-field splitting and to pulse electron-nuclear double resonance experiments. The method is implemented in the software package EasySpin, and several illustrative calculations are shown.

The Semiquinone at the Qi Site of the bc1 Complex Explored Using HYSCORE Spectroscopy and Specific Isotopic Labeling of Ubiquinone in Rhodobacter sphaeroides via 13C Methionine and Construction of a Methionine Auxotroph

“…Spectral processing of ESEEM patterns, including subtraction of the relaxation decay (fitting by polynomials of three to six degrees), apodization (Hamming window), zero filling, and fast Fourier transformation (FT), were performed using Bruker WIN-EPR version 2.22 revision 10. Processed data were then imported into Matlab R2010a via the EasySpin package 39 either to be simulated by EasySpin version 4.5.5 or to be analyzed by a homemade script for fitting data in (ν 1 ) 2 versus (ν 2 ) 2 coordinates. After the HYSCORE had been plotted as (ν 1 ) 2 versus (ν 2 ) 2 , ridges were fit via a linear regression with each point on the ridge weighted according to its HYSCORE intensity (see below).…”

Inhibition of the 4Fe–4S proteins IspG and IspH: an EPR, ENDOR and HYSCORE investigation

“…25 _ENREF_24 To assign the resonances that were observed we next investigated the three selectively 13 C-labeled HMBPPs: spectra are shown in Figure 6B–D. The results of spectral simulations (Figures S5–S9) using EasySpin 26,27 yielded the hyperfine coupling tensors shown in SI Table S3: [1- 13 C], A ii = [−0.7, −0.9, 2.2] MHz; [2- 13 C], A ii = [0.5, 0.7, 4.9] MHz; [3- 13 C], A ii = [3.9, −0.3, −0.1] MHz. Clearly, all three hyperfine interactions are quite small, although those for the 2 and 3-positions (the double bond) are larger than for C-1, consistent again with a weak π-interaction.…”

Spinach – A software library for simulation of spin dynamics in large spin systems

“…ESR-2 is intended for most high-field ESR simulations (possibly involving relaxation, chemical kinetics and anisotropic couplings) and includes a complete basis set on all electrons and anisotropically coupled nuclei, but onlyÊ andT l0 for the isotropically coupled nuclei. This, when used together with the non-interacting subspace separation procedure (Section 2.10), is effectively a generalization of current wisdom about the state spaces encountered in high-field ESR dynamics [73].…”

“…ESR-1 includes the complete state space for all electrons (which are pulsed and observed), but only the identity state andT l0 for the nuclei, taking into account the fact that, in simple pulsed ESR experiments at high field, the transverse nuclear states are never populated [73]. The MARY-1 basis set only includes the ''zero-quantum subspace'' -states with hŜ Z i ¼ 0, taking advantage of the corresponding conservation law.…”