Proton longitudinal relaxation coupling in dynamically heterogeneous soft systems

A quantitative description of water dynamics and water macromolecule interactions is of fundamental importance for both biological and non-biological heterogeneous soft systems. The biological functions for most biomolecules critically depend on the properties of the macromolecule-water interface, and for synthetic polymeric materials and food the effects of hydration on the structural and dynamic properties govern rheological properties and are often fundamental for industrially relevant processes, ultimately determining the applicability of these materials. The Edzes and Samulski model for coupled relaxation has been extensively used to analyze data from different types of experiments, suitably rewriting the coupled Bloch equations according to both the pulse sequence applied and the number of distinguishable proton pools. Magnetization transfer (MT) or cross relaxation spectroscopy, also termed Z-spectroscopy by Grad and Bryant, has been extensively used to obtain information on the spectral lineshape of the macromolecular protons as well as on relaxation in heterogeneous system.