Pseudo field modulation in EPR spectroscopy

Abstract

This paper develops methodology for computer simulation of the effect on an experimental EPR spectrum that would occur ir an additional field modulation were applied followed by eventual phase sensitive detection at the modulation frequency or at one its harmonics. The algo¡ which is called pseudomodulation, transforms the digitized spectrum and also filters the noise. Ir a second harmonic spectrum is desired in order to make subtle changes in curvature more apparent, it is shown that it is always preferable to obtain an expe¡ second harmonic spectrum. The signals are identical, but because of the filtering properties of the pseudomodulation algo¡ the noise is lower. Pseudomodulation should be applied to simulated spectra prior to fitting a model to data in order more precisely to simulate the expe¡ signal. It is argued that such fits ought to involve not only first harmonics but also higher harmonics, since the va¡ harmonics are sensitive in different ways to input parameters in the spin Hamiltonian. Application of pseudomodulation to the EPR spectrum of the blue copper-protein azurin is described.

N2‐to‐NH3 Conversion by a triphos–Iron Catalyst and Enhanced Turnover under Photolysis

“…10 Pulse Q-band ENDOR was acquired using the Davies pulse sequence ( /2 ---echo), where is the delay between mw pulses and RF pulses, is the length of the RF pulse and the RF frequency is randomly sampled during each pulse sequence. For the 2H Davies ENDOR experiments collected from 0.5 -20.…”

Conformational dynamics and distribution of nitroxide spin labels

“…The most efficient way of simulating a CW EPR spectrum from a trajectory LG(t) that describes the dynamics of the g-tensor frame with respect to the laboratory frame consists of the computation of the free induction decay (FID), subsequent Fourier transformation, and pseudomodulation [76] to compute the derivative-like lineshapes. The first implementation sampled a Brownian dynamics trajectory at intervals of 0.3 ns to provide a Nyquist band corresponding to a 100 mT field sweep, assuming a trajectory length of 1 s with 2 14 data points to obtain 30 T resolution [77].…”

Spin distribution of the H-cluster in the Hox–CO state of the [FeFe] hydrogenase from Desulfovibrio desulfuricans: HYSCORE and ENDOR study of 14N and 13C nuclear interactions

“…This length of the microwave pulse was found to be sufficient to suppress field-dependent distortions in the absorption-like spectrum due to the presence of magnetic nuclei. To facilitate the comparison with CW X-band spectra, free induction decay detected spectra were differentiated using the so-called pseudomodulation procedure described by Hyde et al [43].…”