Diffusion equation for the longitudinal spectral diffusion: the case of the RIDME experiment

Abstract

Relaxation-induced dipolar modulation enhancement (RIDME) time trace shapes reveal linear scaling with the proton concentration in homogeneous glassy samples. We describe here an approximate diffusion equation-based analysis of such data,...

A GdIII-Based Spin Label at the Limits for Linewidth Reduction through Zero-Field Splitting Optimization

“…A quantitative analysis of hyperfine interaction with statistically large nuclear reservoirs, as applied in electron spectral diffusion experiments, also allows us to discuss in some detail the feasibility of the proposed solvent-related line broadening. As mentioned, the linewidth change for [Alk 3 -{Gd III (NO3Pic)}] 2 corresponds to the linewidth contribution from the solvent hyperfine interactions of certainly less than 6 Gauss (σ-value in a Gaussian approximation, assuming no correlation between ZFS and hyperfine broadening).…”

“…In our experiments, RIDME outperforms DEER in terms of modulation depth, whereas DEER allows for the detection of longer time traces and has a less steep intermolecular background signal. We would like to point out that a good understanding of the composition of the RIDME background has been achieved, and good fitting models to describe its shape are available. ,, …”

“…We would like to point out that a good understanding of the composition of the RIDME background has been achieved, and good fitting models to describe its shape are available. 50,55,59 The DEER form factor trace was analyzed using the DeerAnalysis GUI version with a model-free distance distribution fit and with a single Gaussian model for the distance distribution (Figure 6b,d). The RIDME form factor trace was analyzed using a single Gaussian model for the distance distribution and with two slightly different sets of dipolar overtone coefficients (Figure 6c,d): 0.51, 0.40, and 0.09 5 and 0.46, 0.40, and 0.14.…”

Quantification of Distributions of Local Proton Concentrations in Heterogeneous Soft Matter and Non-Anfinsen Biomacromolecules

“…Our earlier results justify this approximation and showed a simple relation σ ∝ C H with the conversion factor 0.0214 MHz L mol −1 . 53 By simulating sets of ih-RIDME traces for different proton concentrations in homogeneous samples, we determined time windows where the traces are sensitive to particular concentration ranges (Figure 1e). The steepest ih-RIDME decay is always obtained in the trace recorded with the longest mixing time; here, T mix = 1920 μs.…”

“…The echo signal arises from refocusing after the second π/2 pulses have flipped the grid to the transverse plane. Thus, by leveling the grid longitudinal spectral diffusion (LSD) interferes with refocusing and causes a decay of the echo intensity. , This signal decay due to LSD adds to the RIDME decay due to electron–electron interactions. The LSD-induced decay can be separated from the influence of electron–electron dipolar interaction by variation of the mixing time T mix instead of the dipolar evolution time τ.…”