Intrinsically disordered proteins (IDPs) are challenging established structural biology perception and urge a reassessment of the conventional understanding of the subtle interplay between protein structure and dynamics. Due to their importance in eukaryotic life and central role in protein interaction networks, IDP research is a fascinating and highly relevant research area in which NMR spectroscopy is destined to be a key player. The flexible nature of IDPs, as a result of the sampling of a vast conformational space, however, poses a tremendous scientific challenge, both technically and theoretically. Pronounced signal averaging results in narrow signal dispersion and requires higher dimensionality NMR techniques. Moreover, a fundamental problem in the structural characterization of IDPs is the definition of the conformational ensemble sampled by the polypeptide chain in solution, where often the interpretation relies on the concept of ‘residual structure’ or ‘conformational preference’. An important source of structural information is information-rich NMR experiments that probe protein backbone dihedral angles in a unique manner. Cross-correlated relaxation experiments have proven to fulfil this task as they provide unique information about protein backbones, particularly in IDPs. Here we present a novel cross-correlation experiment that utilizes non-uniform sampling detection schemes to resolve protein backbone dihedral ambiguities in IDPs. The sensitivity of this novel technique is illustrated with an application to the prototypical IDP α-Synculein for which unexpected deviations from random-coil-like behaviour could be observed.

Cd(II) is a major genotoxic agent that readily displaces Zn(II) in a multitude of zinc proteins, abrogates redox homeostasis and deregulates cellular metalloproteome. To date this displacement has been described mostly for cysteine‐rich intraprotein binding sites in certain zinc finger domains and metallothionein. To visualize how Zn(II) to Cd(II) swap can affect the target protein’s status and thus understand the molecular basis of Cd(II)‐induced genotoxicity we focused on an intermolecular Zn(II)‐binding site from the crucial DNA repair protein Rad50 and its zinc hook domain. Using a length‐varied peptide base we hereby demonstrate that Zn(II) to Cd(II) displacement in Rad50’s hook domain alters it in a bimodal fashion: (i) Cd(II) induces around a two‐orders‐of‐magnitude stabilization effect (log K 12 Zn(II) = 20.8 vs log K 12 Cd(II) = 22.7), which defines an extremely high affinity of a peptide towards a metal ion, and (ii) disrupts the overall assembly of the domain, as shown by NMR and anisotropy decay data. Based on our results we propose a novel model explaining the molecular mechanism of Cd(II) genotoxicity that underlines Cd(II)’s impact on Rad50’s dimer stability and quaternary structure that could potentially result in abrogation of the major DNA damage response pathway.

Human serum albumin (HSA) is a monomeric, globular, multi-carrier and the most abundant protein in the blood. HSA displays multiple ligand binding sites with extraordinary binding capacity for a wide range of ions and molecules. For decades, HSA's ability to bind to various ligands has led many scientists to study its physiological properties and protein structure; indeed, a better understanding of HSA-ligand interactions in human blood, at the atomic level, will likely foster the development of more potent, and overall more performant, diagnostic and therapeutic tools against serious human disorders such as diabetes, cardiovascular disorders, and cancer. Here, we present a concise overview of the current knowledge of HSA's structural characteristics, and its coordination chemistry with transition metal ions, within the scope and limitations of current techniques and biophysical methods to reach atomic resolution in solution and in blood serum. We also highlight the overwhelming need of a detailed atomistic understanding of HSA dynamic structures and interactions that are transient, weak, multi-site and multi-step, and allosterically affected by each other. Considering the fact that HSA is a current clinical tool for drug delivery systems and a potential contender as molecular cargo and nano-vehicle used in biophysical, clinical and industrial fields, we underline the emerging need for novel approaches to target the dynamic functional coordination chemistry of the human blood serum albumin in solution, at the atomic level.