Magnetic resonance (Gottingen, Germany)最新文献

Understanding spatially heterogeneous molecular diffusion in semicrystalline polymers is critical for elucidating interfacial dynamics in soft materials. This study employs static-gradient nuclear magnetic resonance (NMR) imaging to capture the depth-resolved translational motion of polymer chains in a polytetrafluoroethylene (PTFE) film. By focusing on spin-spin relaxation behavior in amorphous regions near crystalline lamellae, we identify multiple diffusion regimes consistent with Bloch-Torrey analysis. The results reveal that molecular mobility at the substrate interface of PTFE film, immobilized on a glass substrate using epoxy resin, is significantly constrained, likely due to interfacial pinning, while the air-side surface shows signs of enhanced mobility. Our findings highlight the utility of static-gradient field NMR for probing nanoscale dynamical heterogeneity in semicrystalline systems.

Fast and accurate arbitrary waveform generators (AWGs) for generating shaped pulses in electron paramagnetic resonance (EPR) have been commercially available for over a decade now. However, while the use of chirp pulses as inversion pulses in pulsed electron double resonance (PELDOR) experiments has become common, their application for generating broadband phase-sensitive transverse magnetization is not widely adopted within the community. Here, we give a detailed insight into optimization procedures and instrumental challenges when using chirped pulses for broadband Fourier transform (FT) detection of electron spin echo signals, particularly the two-dimensional frequency-correlated single-frequency technique for refocusing (SIFTER) experiment. To better understand the influence of chirped pulses on the generation of broadband transverse magnetization, we investigated the phase and amplitude of chirped echoes for different time bandwidth products while varying the number of refocusing pulses, particularly under the influence of $B_1$ inhomogeneity. Following our optimization procedures, we were able to perform EPR-correlated 2D-SIFTER measurements using rigid nitroxide spin labels on an RNA duplex. Finally, we also demonstrate the first experiments with two novel SIFTER pulse sequences, which could be of interest for the detection of either shorter or longer distances.

Long-lived states (LLSs) have lifetimes $T_{\mathrm{LLS}}$ that exceed longitudinal spin-lattice relaxation times $T_1$ . In this study, lifetimes $T_{\mathrm{LLS}}$ (¹⁹F) have been measured in three different achiral per- and polyfluoroalkyl substances (PFAS) containing two or three consecutive CF₂ groups. In a static magnetic field $B_0=11.7$ T, the lifetimes $T_{\mathrm{LLS}}$ (¹⁹F) exceed the longitudinal relaxation times $T_1{(}^{19}$ F) by about a factor of 2. The lifetimes $T_{\mathrm{LLS}}$ (¹⁹F) can be strongly affected by binding to macromolecules, a feature that can be exploited for the screening of fluorinated drugs. Both $T_{\mathrm{LLS}}$ (¹⁹F) and $T_1$ (¹⁹F) should be longer at lower fields where relaxation due to the chemical shift anisotropy (CSA) of ¹⁹F is less effective, which is demonstrated here by running experiments at two fields of 11.7 and 7 T.

Using cell-free protein synthesis, the protein G B1 domain (GB1) was prepared with uniform high-level substitution of valine by (2 $S$ ,3 $S$ )-4-fluorovaline, (2 $S$ ,3 $R$ )-4-fluorovaline or 4,4'-difluorovaline. The ${}^{19}F$ nuclear magnetic resonance (NMR) signals are distributed over a wide spectral range. The fluorinated samples maintain the relative ${}^{1}H$ chemical shifts of the wild-type protein, opening a convenient route to assign the ${}^{19}F$ -NMR signals. For the singly fluorinated residues, the ${}^{13}C$  chemical shifts of the remaining ${\mathrm{CH}}_3$ group are subject to a $\gamma$ effect that depends on the population of different rotameric states of the ${\mathrm{CH}}_{2}F$ group and correlates with ${}^3{J}_{\mathrm{FC}}$ coupling constants. In addition, the preferentially populated rotamers are reflected by the $\gamma$ -gauche effect on ${}^{19}F$ chemical shifts, which correlates with ${}^3{J}_{\mathrm{HF}}$ couplings. Some of the side-chain conformations determined by these restraints position the fluorine atom near a backbone carbonyl group, a non-intuitive finding that has previously been observed in the high-resolution crystal structure of a different protein. Through-space scalar ${}^{19}F$ - ${}^{19}F$ couplings due to transient fluorine-fluorine contacts are observed between residues 39 and 54.

Conference travel contributes to the climate footprint of academic research. Here, we provide a quantitative estimate of the carbon emissions associated with conference attendance by analyzing travel data from participants of 10 international conferences in the field of magnetic resonance, namely EUROMAR, ENC and ICMRBS. We find that attending a EUROMAR conference produces, on average, more than 1 t ${\mathrm{CO}}_{2\mathrm{eq}.}$ . For the analyzed conferences outside Europe, the corresponding value is about 2-3 times higher, on average, with intercontinental trips amounting to up to 5 t. We compare these conference-related emissions to other activities associated with research and show that conference travel is a substantial portion of the total climate footprint of a researcher in magnetic resonance. We explore several strategies to reduce these emissions, including the impact of selecting conference venues more strategically and the possibility of decentralized conferences. Through a detailed comparison of train versus air travel - accounting for both direct and infrastructure-related emissions - we demonstrate that train travel offers considerable carbon savings. These data may provide a basis for strategic choices of future conferences in the field and for individuals deciding on their conference attendance.

Combining high-resolution high-field nuclear magnetic resonance (NMR) with an evolution of spin systems at a low magnetic field offers many opportunities for the investigation of molecular motions and hyperpolarization and the exploration of field-dependent spin dynamics. Fast and reproducible transfer between high and low fields is required to minimize polarization losses due to longitudinal relaxation. Here, we introduce a new design of a sample shuttle that achieves remarkably high speeds ( $v_{\max }$ $\sim$ 27 m s^-1). This hybrid pneumatic-mechanical apparatus is compatible with conventional probes at the high-field center. We show applications in water relaxometry in solutions of paramagnetic ions, high-resolution proton relaxometry of a small molecule, and sample shuttling of a solution of a 42 kDa protein. Importantly, this fast sample shuttle (FSS) system is narrow, with a diameter of $d$ $=$ 6 mm for the sample shuttle container based on a standard 5 mm outer diameter glass tube, which should allow near access to the sample for magnetic manipulation at a low field.

Additive manufacturing has enabled rapid prototyping of components with minimum investment in specific fabrication infrastructure. These tools allow for a fast iteration from design to functional prototypes within days or even hours. Such prototyping technologies exist in many fields, including three-dimensional mechanical components and printed electric circuit boards (PCBs) for electrical connectivity, to mention two. In the case of nuclear magnetic resonance (NMR) spectroscopy, one needs the combination of both fields; we need to fabricate three-dimensional electrically conductive tracks as coils that are wrapped around a sample container. Fabricating such structures is difficult (e.g., six-axis micro-milling) or simply not possible with conventional methods. In this paper, we modified an additive manufacturing method that is based on the extrusion of conductive ink to fast-prototype solenoidal coil designs for NMR. These NMR coils need to be as close to the sample as possible and, by their shape, have specific inductive values. The performance of the designs was first investigated using electromagnetic field simulations and circuit simulations. The coil found to have optimal parameters for NMR was fabricated by extrusion printing, and its performance was tested in a 1.05 $T$ imaging magnet. The objective is to demonstrate reproducible rapid prototyping of complicated designs with high precision that, as a side effect, hardly produces material waste during production.

The implementation of parallel nuclear magnetic resonance detection aims to enhance measurement throughput in support of high-throughput-screening applications, including, for example, drug discovery. In support of modern pulse sequences and solvent suppression methods, each detection site must have independent pulsed field gradient capabilities. Hereby, a challenge is introduced in which the local gradients applied in parallel detectors introduce field spillover into adjacent channels, leading to spin dephasing and, hence, to signal suppression. This study proposes a compensation scheme employing optimized pulses to achieve coherence locking during gradient pulse periods. The design of coherence-locking pulses utilizes optimal control to address gradient-induced field inhomogeneity. These pulses are applied in a pulsed-gradient spin echo (PGSE) experiment and a parallel heteronuclear single quantum coherence (HSQC) experiment, demonstrating their effectiveness in protecting the desired coherences from gradient field spillover. This compensation scheme presents a valuable solution for magnetic resonance probes equipped with parallel and independently switchable gradient coils.