Preprints  

Shaped radiofrequency pulses are widely used in NMR spectroscopy to provide selective excitation or inversion of magnetization. Efficient accurate methods for calculating the performance of such pulses enable understanding of existing pulses and facilitate optimization of new pulses. A new approach for approximating the effects of shaped pulses is introduced and applied to some popular shaped pulses as examples. This approach also will be useful in other areas of theoretical NMR spectroscopy.

We show here that information about protein molecular dynamics can be directly extracted out of a single NMR spectrum. Understanding protein dynamics is essential to understanding its function, energetics and biology. We hope that this contribution helps bring this insight to a much broader application field and audience community than previously possible.

While most proteins adopt a single well-folded structure, several are known which interconvert among two or more conformations. Here we examine one system which is in equilibrium between two folds differing by a +3 shift in beta-strand register, describing sequence and environmental factors that bias the populations of the two structures. Notably, small molecule binding shifts the equilibrium, setting ways to artificially control natural or engineered proteins with this domain.

¹³C spin hyperpolarization using laser irradiation at room temperature is shown in two different systems: 1. Pentacene doped in an organic crystal of benzoic acid and 2. Nitrogen-Vacancy (NV) color centers in microdiamonds. The ¹³C NMR signal was enhanced by a factor of > 3000 using pentacene and > 300 using NV centers as a polarization source. We analyze the pros and cons of these two systems and discuss their prospects for room-temperature enhancement of NMR signals.

The application of anisotropic NMR parameters for the correct structural assignment of small molecules requires the use of partially ordered media. Previously we demonstrated that P3D simulations allows the determination of the correct diastereomer. Here we show that when steric or electrostatic factors dominate the alignment, P3D retains its diastereomer discrimination power and can define conformational ensembles of flexible molecules from sparse NMR data.

The efficiency of the MRI contrast agents can increase by exploiting magnetization transfer effects occurring in slow-rotating nanoparticles containing a paramagnetic metal ion and a large number of exchangeable surface protons. Occurrence of magnetization transfer should also be considered to determine accurate metal-proton distances, used for protein structure determination, from the experimental proton relaxation rates.

The demonstration of the Finite Pulse Radio Frequency Driven Recoupling experiment was firstly published over the past 20 years. Since it has become one of the used experiments. In this article we consider that experiment using other theoretical and simulated approaches with respect to the previous works. These approaches help us to understand more clearly the influence of each part of that experiment and to see how exactly the spin system is evaluated during it.

Modern contrast agents for MRI lead to new methods for e.g. cancer diagnosis. One of these promising methods is called PHIP (Para-Hydrogen Induced Polarization) and can be performed at low instrumentation costs. However, it is based on para-hydrogen which has to be produced on-site. Since commercial generators cost up to 150,000 €, we decided to provide the blueprints of our generator (< 3,000 €) as open-source to enable more groups to build their own generator and enter this research field.

We recently added 2D NMR spectroscopy to the well-established techniques able to obtain information on the process of unfolding using resonances of residues in the hydrophobic core of a protein. We asked whether a detailed analysis of the individual stability curves could provide additional site-specific information. By monitoring both cold and heat denaturation of individual residues we convincingly demonstrate that the two unfolding processes are intrinsically different.

Nowadays, almost all MRI technique used in clinical applications are based on a Fourier transformation of the raw data. Alternative non-Fourier magnetic resonance imaging techniques can offer some advantages under certain conditions. SPatio-temporal ENcoding (SPEN) is a non-Fourier method that usually employs frequency-swept radio frequency pulses and can give good images in inhomogeneous magnetic fields. In this work we show how one can improve this technique by using quadratic gradients.