Low field nuclear magnetic resonance spectroscopy of hyperpolarized spin systems

Results of the dissertation must be divided into three sections. The first section is concerned with construction of a magnet system suitable for high-resolution low-field nuclear magnetic resonance spectroscopy which was planned, prepared and evaluated. In the following, the newly developed experimental setup was used for low-field nuclear magnetic resonance experiments in combination with hyperpolarization. In the second section the new setup was used for spectroscopy of hyperpolarized xenon and investigation of the Spin Polarization Induced Nuclear Overhauser Effect. In the third section parahydrogen induced polarization was investigated experimentally and theoretically. To Section 1: Due to the high precision requirements spectroscopy grade magnets all coils (1 mean field coil, 4 shim coils) were carefully measured and, if required, remade. The system was tested with current sources differing in temporal stability and theoretically and experimentally achievable homogeneities were compared. To Section 2: SPINOE Experiments in this section (1) revealed, that SPINOE is not limited to unpolar organic molecules. Furthermore, it was shown experimentally that the so-called "strongly coupled spin systems" exists at higher field strengths, where as expected, large heteronuclear coupling constants present in inorganic molecules shift the strong coupling regime to from earth's magnetic field to several mT fields.To Section 3: In order to advance the state of the theory of para-hydrogen induced polarization (PHIP) a compound suitable for investigation with the new setup under the restrictions imposed by the the performance parameters determined in section 1 was prepared. A suitable catalyst system for catalytic hydrogenation step of the para-hydrogen induced polarization step was localized. In the following the system was investigated by spectroscopy at different magnetic field strengths, made possible by the system constructed in section 1. The results obtained were used to derive and verify (2) the heteronuclear three-spin density matrix, which is a key reference point for PHIPexperiments. (1) Experiments were performed in Collaboration with the ERS visitors Prof. K. Ishikawa, Kyoto University and Dr. B. Patton, UC Berkeley. (2) In collaboration with M.Sc. P. Türschmann and Prof. S. Appelt

Low field nuclear magnetic resonance spectroscopy of hyperpolarized spin systems

Results of the dissertation must be divided into three sections. The first section is concerned with construction of a magnet system suitable for high-resolution low-field nuclear magnetic resonance spectroscopy which was planned, prepared and evaluated. In the following, the newly developed experimental setup was used for low-field nuclear magnetic resonance experiments in combination with hyperpolarization. In the second section the new setup was used for spectroscopy of hyperpolarized xenon and investigation of the Spin Polarization Induced Nuclear Overhauser Effect. In the third section parahydrogen induced polarization was investigated experimentally and theoretically. To Section 1: Due to the high precision requirements spectroscopy grade magnets all coils (1 mean field coil, 4 shim coils) were carefully measured and, if required, remade. The system was tested with current sources differing in temporal stability and theoretically and experimentally achievable homogeneities were compared. To Section 2: SPINOE Experiments in this section (1) revealed, that SPINOE is not limited to unpolar organic molecules. Furthermore, it was shown experimentally that the so-called "strongly coupled spin systems" exists at higher field strengths, where as expected, large heteronuclear coupling constants present in inorganic molecules shift the strong coupling regime to from earth's magnetic field to several mT fields.To Section 3: In order to advance the state of the theory of para-hydrogen induced polarization (PHIP) a compound suitable for investigation with the new setup under the restrictions imposed by the the performance parameters determined in section 1 was prepared. A suitable catalyst system for catalytic hydrogenation step of the para-hydrogen induced polarization step was localized. In the following the system was investigated by spectroscopy at different magnetic field strengths, made possible by the system constructed in section 1. The results obtained were used to derive and verify (2) the heteronuclear three-spin density matrix, which is a key reference point for PHIPexperiments. (1) Experiments were performed in Collaboration with the ERS visitors Prof. K. Ishikawa, Kyoto University and Dr. B. Patton, UC Berkeley. (2) In collaboration with M.Sc. P. Türschmann and Prof. S. Appelt

Fundamental Aspects of Parahydrogen Enhanced Low-Field Nuclear Magnetic Resonance

We report new phenomena in low-field 1H nuclear magnetic resonance (NMR) spectroscopy using parahydrogen induced polarization (PHIP), enabling determination of chemical shift differences, δν, and the scalar coupling constant J. NMR experiments performed with thermal polarization in millitesla magnetic fields do not allow the determination of scalar coupling constants for homonuclear coupled spins in the inverse weak coupling regime (δν<J). We show here that low-field PHIP experiments in the inverse weak coupling regime enable the precise determination of δν and J. Furthermore we experimentally prove that observed splittings are related to δν in a nonlinear way. Naturally abundant 13C and 29Si isotopes lead to heteronuclear J-coupled 1H-multiplet lines with amplitudes significantly enhanced compared to the amplitudes for thermally prepolarized spins. PHIP-enhanced NMR in the millitesla regime allows us to measure characteristic NMR parameters in a single scan using samples containing rare spins in natural abundance

Direct Transformation Of Amino Acids Into Diazirines And 15N2-Diazirines And Their Application As Hyperpolarized Markers

International audienc

Direct Transformation Of Amino Acids Into Diazirines And 15N2-Diazirines And Their Application As Hyperpolarized Markers

International audienc

Terminal Diazirines Enable Reverse Polarization Transfer from 15 N 2 Singlets

International audienceDiazirine moieties are chemically stable and have been incorporated into biomolecules without impediment of biological activity. The 15N2 labeled diazirines are appealing motifs for hyperpolarization supporting relaxation protected states with long‐lived lifetimes. The (‐CH15N2) diazirine groups investigated here are analogues to methyl groups, which provides the opportunity to transfer polarization stored on a relaxation protected (‐CH15N2) moiety to 1H, thus combining the advantages of long lifetimes of 15N polarization with superior sensitivity of 1H detection. Despite the proximity of 1H to 15N nuclei in the diazirine moiety, 15N T1 times of up to (4.6±0.4) min and singlet lifetimes Ts of up to (17.5±3.8) min are observed. Furthermore, we found terminal diazirines to support hyperpolarized 1H2 singlet states in CH2 groups of chiral molecules. The singlet lifetime of 1H singlets is up to (9.2±1.8) min, thus exceeding 1H T1 relaxation time (at 8.45 T) by a factor of ≈100

Diazirine 14N/15N isotopomers: chirality and hyperpolarization

International audienc

Iodonitrene in Action: Direct Transformation of Amino Acids into Terminal Diazirines and 15 N 2 -Diazirines and Their Application as Hyperpolarized Markers

International audienceA one-pot metal-free conversion of unprotected amino acids to terminal diazirines has been developed using phenyliodonium diacetate (PIDA) and ammonia. This PIDA-mediated transformation occurs via three consecutive reactions and involves an iodonitrene intermediate. This method is tolerant to most functional groups found on the lateral chain of amino acids, it is operationally simple, and it can be scaled up to provide multigram quantities of diazirine. Interestingly, we also demonstrated that this transformation could be applied to dipeptides without racemization. Furthermore, 14 N 2 and 15 N 2 isotopomers can be obtained, emphasizing a key trans-imination step when using 15 NH 3. In addition, we report the first experimental observation of 14 N/ 15 N isotopomers directly creating an asymmetric carbon. Finally, the 15 N 2-diazirine from L-tyrosine was hyperpolarized by a parahydrogen-based method (SABRE-SHEATH), demonstrating the products' utility as hyperpolarized molecular tag

Direct Transformation Of Amino Acids Into Diazirines And 15N2-Diazirines And Their Application As Hyperpolarized Markers

International audienc