Nuclear magnetic resonance is a technique that allows the measurement of the nanoscale distances between the atoms of a molecule. It is often relied upon for finding the structure of a molecule and how atoms are bonded, but measurements become inaccurate for large distances and therefore for large biological molecules. This research presents a new software for calculating the distances between nuclei and unpaired electrons which offers more accurate long-range distances in biological molecules.

This paper analyzes a commonly used line-narrowing mechanism (homonuclear decoupling) in solid-state NMR and discusses what limits the achievable line width. Based on theoretical considerations, the contribution of different effects to the line width is discussed and a new contributing term is identified. This research allows us to evaluate new ways to improve the line width in such homonuclear decoupled spectra.

Detailed interpretation of brain MRI data is hampered by the fact that each imaging voxel comprises several types of cells and tissues. To address this, we adapt signal encoding and data inversion strategies from solid-state and low-field NMR to quantify the sub-voxel heterogeneity of the human brain with 5D relaxation–diffusion distributions wherein distinct tissue components are resolved, individually characterized, and subsequently mapped throughout the volume of the brain.

DNP is a method used to enhance NMR signals by transferring polarization from radicals to nuclear spins using microwave irradiation. The EPR spectrum of the radical during the irradiation is determined by a process called spectral diffusion and affects the DNP efficiency. This process can be measured by electron–electron double resonance. We explored experimentally and theoretically the contribution of the hyperfine coupling of the ¹⁴N nuclei in the nitroxide radical to the spectral diffusion.

The determination of distance distributions in the nanometre range is an important application of pulsed electron paramagnetic resonance spectroscopy. However, low sensitivity is often a major challenge. In this paper, we compare several broadband-shaped pulses and compare their performance to classical rectangular pulses in order to increase the sensitivity of double electron–electron resonance to a commercial setup. We show that improvements in sensitivity of up to 86 % are possible.

Measuring distances between unpaired electron spins is an important application of electron paramagnetic resonance. The longest distance that is accessible is limited by the phase memory time of the electron spins. Here we show that strong continuous microwave irradiation can significantly slow down relaxation. Additionally, we introduce a phase-modulation scheme that allows measurement of the distance during the irradiation. Our approach could thus significantly extend the accessible distances.

A dipolar cross-polarization (dCP) sequence employing simple radiofrequency pulse shapes with reduced power requirements is demonstrated to transfer proton polarization to insensitive heteronuclei.

We have recently demonstrated the capability to rapidly spin spherical rotors inclined precisely at the magic angle (54.74°) with respect to the external magnetic field used for nuclear magnetic resonance (NMR) experiments. We show that it is possible to spin a spherical rotor without using turbine grooves and that these rotors are extremely stable because of the inherent spherical-ring geometry. These results portend the facile implementation of spherical rotors for solid-state NMR experiments.

We have assembled a few off-the-shelf electronic chips and a popular Arduino Uno microcomputer board in an automatic system that performs so-called tuning and matching of an arbitrary NMR probe head at very low cost. This removes the tedium of doing the job by hand, the bane of many NMR analysts. It also brings accuracy and repeatability into the process, which is so necessary for high throughput analysis or when working with low-field permanent magnesystems with excessive magnetic field drift.

The combination of magnetic resonance with laser spectroscopy provides some interesting options for increasing the sensitivity and information content of magnetic resonance by many orders of magnitude. This review covers the basic physics behind the relevant processes, such as angular momentum conservation during absorption and emission.

Quantitative analysis of mixtures is a challenge in applications ranging from foods to industrial chemistry. Nuclear magnetic resonance (NMR) is increasingly used for analysis; however, overlapping peaks in the spectrum pose a major difficulty, especially for the new generation of benchtop NMR instruments. We propose a fast and simple model-based approach to enhance the accuracy of quantification. We demonstrate it on industrially relevant test samples where the accuracy is increased by 40 %.

The cosmetic industry integrates in its products active ingredients of vegetal origin. For this purpose, plant extracts are prepared and their content must be characterized to check their conformity with safety regulations. Many plant extracts contain a high proportion of high-boiling-point solvents that may conflict with analytical protocols. Extract analysis by fractionation and subsequent ¹³C NMR analysis required a new solvent signal suppression technique to provide better analytical data.

For the first time, a three-dimensional map of the distribution of water in a test sample has been obtained from the random radio signal (spin noise) emitted spontaneously by hydrogen nuclei in a magnetic field with varying field gradients. A special variant of a projection–reconstruction algorithm has been developed for noise data, which allows one to adjust the image quality between high resolution/low contrast and low resolution/high contrast from the same previously recorded spin noise data.

We explored hydrogenation reaction with a para-spin isomer of a hydrogen molecule as a source of nuclear singlet state. As a product of this reaction, the state was populated between two protons of the methylene group. We have shown that, utilizing long-lived properties of such a nuclear spin state, a high nuclear spin polarization can be accumulated. To explain this effect we have given a kinetic model which could be potentially applied for similar schemes involving spin dynamics in chemistry.

Resonant pulses in a spin-lock frame are used to select parts of the rf-field distribution in NMR experiments. Such pulses can be implemented in a straightforward way and arbitrarily shaped pulses can be used. We show an application of such pulses in homonuclear decoupling where restricting the amplitude distribution of the rf field leads to improved performance.

The stable, two-atomic radical NO, which is an important biophysical messenger, was studied with magnetic resonance methods. Caused by its specific electronic configuration, it has sensor properties: its magnetic moment sensitively depends on its environment and restricted mobility therein. The interaction with solvents or solid phases can thus be quantified. Encapsulating the radical in the nearly spherical cage of modified C₆₀ fullerenes is a perfect situation to study this effect.

Dipolar electron paramagnetic resonance spectroscopy methods such as DEER provide data on how proteins change shape, thus giving detailed insight into how proteins work. We present DeerLab, a comprehensive open-source software for reliably analyzing the associated data. The software implements a series of theoretical and algorithmic innovations and thereby improves the quality and reproducibility of data analysis.

Magnetic resonance detectors require a high degree of precision to be useful. Their design must e.g. carefully weigh field strength and field homogeneity to find the best compromise. Here we show that inverse computational design is a viable method to find such a trade-off. Apart from the electromagnetic field solution, the simulation program also determines the boundary between insulating and conducting material and moves the material boundaries around until the compromise is best satisfied.

We studied spin dynamics in nuclear spin systems at low magnetic fields, where strong coupling among nuclear spins of the same kind, here ¹³C, is expected. Such conditions are known to be favorable for coherent polarization transfer. However, to our surprise, interactions with other nuclei, i.e., protons, lead to a breakdown of the strong coupling conditions. By using a two-field nuclear magnetic resonance approach, we can manipulate low field-spin dynamics and reintroduce strong coupling.

This work presents systematic methodological study of one of the types of the nuclear magnetic resonance experiments that enables study of molecular dynamics on a millisecond timescale. A modification of a standard experiment was suggested that excludes possible artefacts and distortions. It has been demonstrated that the standard experiment reveals slow overall motion of proteins in a rigid crystal lattice, whereas the artefact-free experimental setup demonstrates that the proteins are rigid.

Natural photosynthetic reaction centers (RCs) are built up by two parallel branches of cofactors. While photosystem II and purple bacterial RCs selectively use one branch for light-driven electron transfer, photosystem I, as also shown here, is using both branches. Comparing NMR chemical shifts, we shown that the two donor cofactors in photosystem I are similarly distinguished to those in purple bacterial RCs (Schulten et al., 2002; Biochemistry 41, 8708). Alternative reasons are discussed.

The sensitivity of magnetic resonance imaging can be increased by coupling of the less sensitive nuclear spins which are excited at radio frequencies to unpaired electron spins of radicals which are excited at microwave frequencies. Here we demonstrate how a Fabry–Perot-type microwave resonance structure can be used to significantly enhance the polarization transfer from electron to water proton nuclear spins under constant flow conditions for imaging applications at 1.5 T.

With a pulsed dipolar electron paramagnetic resonance technique named double electron–electron resonance (DEER), we measure nanometer distances between spin labels attached to biomolecules. If more than one spin type is present (A and B), we can separately address AA, AB, and BB distances via distinct spectroscopic channels, increasing the information content per sample. Here, we investigate the appearance of unwanted channel crosstalks in DEER and suggest ways to identify and suppress them.

Through a series of DEER measurements on two Gd rulers, with Gd–Gd distances of 2.1 and 6.0 nm, we show that artefacts commonly observed when measuring short distances can be eliminated by avoiding excitation of the central transition by both the pump and observer pulses. By using a wideband induction mode sample holder at 94 GHz, we demonstrate that high-quality DEER measurements will become possible using Gd spin labels at sub-µM concentrations, with implications for in-cell DEER measurements.

Electron spin detection was recently demonstrated using superconducting circuits and amplifiers at millikelvin temperatures, reaching the quantum limit of sensitivity. We use such a setup to measure electron-spin-echo envelope modulation on a small number of electron spins, in two model systems: bismuth donors in silicon and erbium ions doped in CaWO₄ (calcium tungstate). Our results are a proof of principle that hyperfine spectroscopy is feasible with these quantum-limited ESR spectrometers.

We introduce ssNMRlib, a library of pulse sequences and jython scripts for user-friendly setup and acquisition of solids-state NMR experiments. ssNMRlib facilitates all steps of data acquisition, including calibration of various pulse-sequence parameters and semi-automatic setup of even complex high-dimensional experiments, using an intuitive graphical user interface, launched directly within Bruker's Topspin acquisition program.

This work discusses nuclear magnetic resonance (NMR) experiments, which make use of coherent spin evolution at level anti-crossings. In this work, we provide a common description of such phenomena (hopefully, a reasonably simple one), which is illustrated by a number of examples from various subfields of NMR.