Pseudocontact shifts from mobile spin labels

TL;DR

This paper analyzes how mobile spin labels affect pseudocontact shifts, showing that non-spherical distributions can cause deviations from point dipole models and proposing methods to reconstruct paramagnetic center distributions from experimental data.

Contribution

It introduces a detailed analysis of PCS induced by mobile spin labels considering non-spherical distributions and provides analytical, numerical solutions and reconstruction techniques.

Findings

Non-spherical density causes deviations from point dipole approximation.

Analytical and numerical solutions for the general PDE are provided.

Reconstruction of paramagnetic center distributions from PCS data is feasible.

Abstract

This paper presents a detailed analysis of the pseudocontact shift (PCS) field induced by a mobile spin label that is viewed as a probability density distribution with an associated effective magnetic susceptibility anisotropy. It is demonstrated that non-spherically-symmetric density can lead to significant deviations from the commonly used point dipole approximation for PCS. Analytical and numerical solutions are presented for the general partial differential equation that describes the non-point case. It is also demonstrated that it is possible, with some reasonable approximations, to reconstruct paramagnetic centre probability distributions from the experimental PCS data.