Leipzig Spin Resonance Colloquium
When small is beautiful in magnetic resonance
For select applications, and especially when samples are naturally small, or small for technical reasons, the NMR system must accomodate this vanishing sample size, which implies the use of miniaturized detection and sample handling sub-systems. In my presentation I will thus address the challenge of achieving the required miniaturization of NMR hardware for sample sizes of around one microlitre and less. I will illustrate the ways we gain control over the patterning of NMR-compatible materials at the microscale, and discuss some of the detection (sub-) systems that my group has established with these processes over the past five years or so. This will include a demonstration of the sort of measurements we can achieve by these systems.
Genes, Cells, and Magnetic Resonance Imaging
Symmetry-Based NMR Pulse Sequences in Solids and Liquids
NMR pulse sequences may be designed in such a way that they impose a symmetrical pattern in time and space on the nuclear spin dynamics. This approach leads to selection rules on the average Hamiltonian, which governs the main operating principle of the pulse sequence. The selection rules depend on a small set of integers, called symmetry numbers, which may be chosen to select terms of interest while suppressing the effect of interfering terms. In magic-angle-spinning solid-state NMR, this approach has been used for some time, to implement robust solutions to a variety of problems, such as double-quantum and zero-quantum dipolar recoupling, and the recoupling of chemical shift anisotropy interactions.
Recently, we have shown that the symmetry-based approach to pulse sequence design is also useful for certain spin dynamical problems in solution NMR. These include the robust conversion of magnetization to long-lived singlet order in near-equivalent spin-pair systems. We show that the PulsePol sequence, which has been used for a variety of tasks in nitrogen-vacancy magnetometry, may be understood as a riffled version of a symmetry-based pulse sequence, and used for robust singlet-triplet conversion in solution NMR.
In my talk I will review the principles of symmetry-based pulse sequence design and discuss how this approach leads to rapid and general solutions to a variety of spin dynamical problems in both solution NMR and solid-state NMR.
For our recent paper see http://arxiv.org/abs/2206.07109
Hyperpolarization with parahydrogen
Since many years PHIP (Parahydrogen Induced Polarization) and its reversible variant SABRE (Signal Amplification By Reversible Exchange) are among the most versatile tools for NMR signal enhancement in solution NMR. In the present talk we first give a short introduction into PHIP and SABRE, followed by several examples from our recent work. The first example shows results from our investigations of a bioactive derivative of the sunflower trypsin inhibitor-1 (SFTI-1), which inhibits matriptase, a colon cancer related enzyme. The PHIP activity of the inhibitor was achieved by labeling the tetradecapeptide with O-propargyl-L-tyrosine. Employing a carefully optimized automatized PHIP setup  in 1D-PHIP experiments an enhancement of up to ca. 1200 compared to normal NMR was found.[2,3] This huge enhancement factor permitted the ultrafast single scan detection of 2D-TOCSY spectra of micromole solutions of the PHIP labelled inhibitor. The second example discusses the application of parahydrogen for the detection of low-concentrated intermediates of hydrogenation reactions via the PANEL (PArtial NEgative Line experiment). The third example describes some recent results on substituent influences on the SABRE activity of Iridium complexes with heterocyclic carbene ligands. Then we present recent results on the hyperpolarization of fumarate and eptifibatide, an antiplatelet aggregation inhibitor, which derives from the venom of certain rattlesnakes
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