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We develop an exact analytical description of spinning sideband intensities in magic-angle spinning NMR, e.g., for 13C CSA. This can be used in spectral fitting to obtain tensor parameters and plays out its advantage in the analysis of orientation effects in non-isotropic samples. We present an improved approach to process data obtained with the simple syncMAS experiment, which is powerful but not very popular due to the as yet not very transparent and difficult data analysis.

We use the theory of magnetostatic reciprocity to compute manufacturable solutions of complex magnet geometries, establishing a quantitative metric for the placement and subsequent orientation of discrete pieces of permanent magnetic material. This leads to self-assembled micro-magnets, adjustable magnetic arrays, and an unbounded magnetic field intensity in a small volume, despite realistic modelling of complex material behaviours.

Multidimensional NMR relaxation experiments provide a powerful means of studying protein dynamics but typically require long acquisition times. Here, we combine two approaches that individually shorten the length of the experiment: accordion spectroscopy and non-uniform sampling (NUS). We extract relaxation rate constants by applying maximum likelihood estimation of sparse exponential modes modeled on the accordion–NUS interferograms, resulting in time savings by a factor of roughly 10.

Nuclear magnetic resonance spectroscopy is at the forefront of analytical methods used in organic chemistry and phytochemistry. Multiplet structure deconvolution has been revisited in the perspective of a robust integration in the computer-assisted workflow of 1D spectra analysis. New features include the management of coupling partners with spin > 1/2, second-order effects and partial signal overlap.

Unlike rigid folded proteins, intrinsically disordered proteins (IDPs) exist as an ensemble of dynamically interconverting structures. Cross-correlated spin-relaxation experiments are particularly suited to characterize the structural dynamics of IDPs as they encode a protein's structural memory. By translating diffusion models of folded proteins to segmental motions in IDPs, we define and assess a sensitive experimental measure for the presence of anisotropic dynamics in the protein backbone.

NMR represents a key spectroscopic technique for studying intrinsically disordered proteins (IDPs) that lack a stable three-dimensional structure. We present a set of NMR experiments tailored for proline residues, which are highly abundant in IDPs. The novel experiments have very interesting properties for the investigation of IDPs of increasing complexity.

The radio-frequency (rf) field amplitude in solid-state NMR probes changes over the sample volume, i.e. different parts of the sample will experience different nutation frequencies. If the sample is rotated inside the coil as it is typical for magic angle spinning in solid-state NMR, such a position-dependent inhomogeneity leads to an additional time dependence of the rf field amplitude. We show that such time-dependent modulations do not play an important role in many experiments.

Sample rotation around the magic angle averages out the dipolar couplings in homonuclear spin systems in a first-order approximation. However, in higher orders, residual coupling terms remain and lead to a broadening of the spectral lines. We investigate the source of this broadening and the effects on the powder line shape in small spin systems with and without chemical shifts. We show that one can expect different scaling behavior as a function of the spinning frequency for the two cases.

In drug discovery, ready access to accurate atomic resolution information revealing conformations and dynamics of novel small molecules in solution guides rational design to optimize drug potency and physical chemistry. We developed an efficient integration of molecular dynamics calculations and visualization protocols with NMR conformational analysis of free ligands in solution. Agreement between experiment and theory inspires confidence in prospective computational analysis of new designs.

Isotope filters are pivotal for studying interactions between labelled and unlabeled moieties by NMR. We present an isotope filter method to complement existing filters and attenuate undesired signals that escaped them. This advance will readily facilitate molecular studies of binding events or post-translational modifications by NMR.

The transfer of polarization from protons to half-integer spin quadrupolar nuclei provides insights into the proximities between these nuclei. We analyse the best transfers at 20 and 62 kHz MAS obtained with RINEPT and PRESTO recouplings using adiabatic or composite π pulses. The 1H magnetization is best transferred using PRESTO-R22,7,2 (180) or -R16,6,7 (270,90) at 20 or 62 kHz MAS, respectively, and RINEPT-SR4,2,1 (270,90).

This publication presents research in biomolecular NMR, spin hyperpolarisation and spin chemistry. Robert Kaptein made key contributions to magnetic resonance and proposed the radical pair mechanism for chemically induced dynamic nuclear polarisation (CIDNP). He developed laser CIDNP and computational methods for protein structure determination. He is known for studying the lac repressor and its DNA complexes. He played a leading role in establishing the NMR large-scale facilities in Europe.

An approach is described for formulating the kinetic master equations of the time evolution of hyperpolarized NMR signals in reacting (bio)chemical systems. We take a stepwise approach to formulate mathematical models of enzyme systems that agree with standard descriptions of (bio)chemical kinetics while remaining capable of describing the time evolution of magnetization described by the Bloch–McConnell equations.

The use of hyperpolarized species, i.e., species whose nuclear polarization is transiently multiplied by several orders of magnitude, can perfectly be combined with the use of benchtop NMR spectrometers. In particular, laser-polarized ¹²⁹Xe, due to its large chemical shift range and the proximity of its resonance frequency to ¹³C, can be observed on a non-dedicated low-field spectrometer. Detection of low amounts of molecules can be achieved using NMR techniques based on chemical exchange.

Magnetic resonance experiments are described using a mathematical object called the spin density operator. The article explores the regions of an abstract space called Liouville space which may be occupied by the density operator. The study is of particular relevance to hyperpolarized magnetic resonance, which is capable of generating greatly enhanced nuclear magnetic resonance signals which may be used, amongst other things, for imaging of metabolism in the human body.

Trigger factor (TF) is a conserved bacterial molecular chaperone that exists in a monomer–dimer equilibrium in solution. It binds to the ribosome as a monomer to facilitate folding of nascent polypeptide chains. We showed that dimeric TF exhibits distinct domain dynamics and conformational polymorphism and that TF contains multiple substrate binding sites that are only accessible in its monomeric form. The equilibrium of TF in different oligomeric states may serve as a regulatory mechanism.

We present a system for facilitated sample vitrification, melting, and transfer in dissolution dynamic nuclear polarization experiments. The system enables insertion of a sample through an airlock in combination with a dedicated dissolution system that is inserted through the same airlock shortly before the melting event. The cryostat can thus be operated continuously at low temperatures, and the melting process is rapid as no pressurization steps of the cryostat are necessary for dissolution.

The Wnt signalling pathway plays a major role in prevention of cancer, whereby the protein Dishevelled connects from the transmembrane receptor Frizzled to downstream effectors via its PDZ domain. Here, cycles of chemical synthesis and structural biology are applied to develop PDZ ligands that block the Frizzled–Dishevelled interaction using NMR for screening, in ligand development, and for deriving structure–activity relationships. Cellular reporter assays demonstrate their efficacy.

The RFDR sequence has been widely used for homonuclear recoupling. The paper describes a heteronuclear version of RFDR. HET-RFDR sequence transfers longitudinal polarization between heteronuclear pairs by applying RFDR on two channels simultaneously. We perform an operator analysis of HET-RFDR and RFDR. Such an analysis allows for better understanding of the influence of offsets and paths of magnetization transfers for both these experiments, as well as the crucial role of XY phase cycling.

This is an obituary for Konstantin Lvovitch Ivanov.

Reversible para-hydrogen-induced polarization (PHIP) is a technique to enhance NMR signals in solution, based on the association/dissociation of para-hydrogen and substrate molecules with/from an iridium catalyst. In this work we present an approach to measure NMR relaxation as well as rate constants of para-hydrogen association/dissociation with/from the iridium catalyst. These rates are important for understanding the different PHIP efficiencies observed for different substrate molecules.

Derivatives of the amino acids tryptophan and tyrosine were studied in their potential to enhance their signal in nuclear magnetic resonance spectroscopy (NMR) by laser-induced dynamic nuclear polarisation (CIDNP). Signal enhancement up to two orders of magnitude was obtained.

The folding, refolding and misfolding of biomacromolecules including proteins, DNA and RNA is an important area of biophysical research to understand functional and disease states of a cell. NMR spectroscopy provides detailed insight, with both high time and atomic resolution. These experiments put stringent requirements on signal-to-noise for often irreversible folding reactions. The review describes methodological approaches and highlights key applications.

Methyl groups are rarely acidic. But in a lumazine derivative with biological significance the position-7 methyl group can be deprotonated. The existence of two protonation states is a prerequisite for a non-classical disproportionation reaction initiated by light. We provide evidence for such dismutation using a variant of nuclear magnetic resonance that is capable of detecting nuclear hyperpolarization. Our findings may shed new light on enzymatic riboflavin biosynthesis.

This work presents a setup for the investigation of electrochemical processes during operation (in operando) using nuclear magnetic resonance (NMR) spectroscopy. The setup was designed to minimize the interferences between the NMR instrument and the electrochemical equipment. Employing this setup, the dynamic equilibrium of carbon dioxide in aqueous bicarbonate electrolyte has been monitored in operando, revealing intercations with the electrode setup.

NMR relaxation rate constants are powerful probes of the functional dynamics of biological macromolecules, such as proteins and nucleic acids. However, variations in choice of models used to analyze relaxation data obscure variations due to critical biological or chemical effects. Bootstrap aggregation, a recently developed statistical method, circumvents the model selection problem and enables more consistent and insightful interpretation of NMR relaxation data.

Dynamic nuclear polarization (DNP) magic angle spinning NMR yields huge signal enhancements and is attractive for signal-limited cases. We studied polarization transfer pathways underlying sensitivity and resolution in DNP experiments on tubular assemblies of HIV-1 CA protein. All three polarization transfer pathways are simultaneously active and can be selected by carefully choosing experimental conditions. Our study highlights the unique capabilities of DNP for structural biology applications.