Communication: partial polarization transfer for single-scan spectroscopy and imaging.

A method is presented to partially transfer nuclear spin polarization from one isotope S to another isotope I by the way of heteronuclear spin couplings, while minimizing the loss of spin order to other degrees of freedom. The desired I spin polarization to be detected is a design parameter, while the sequence of pulses at the two Larmor frequencies is optimized to store the greatest unused S spin longitudinal polarization for subsequent use. The unitary evolution for the case of I(N)S spin systems illustrates the potentially ideal efficiency of this strategy, which is of particular interest when the spin-lattice relaxation time of S greatly exceeds that of I.

Nanoscale torsional resonator for polarization and spectroscopy of nuclear spins.

We propose a torsional resonator that couples to the transverse spin dipole of an attached sample. The absence of relative motion eliminates a source of friction that would otherwise hinder nanoscale implementation. Enhanced spontaneous emission induced by the resonator relaxes the longitudinal spin dipole at a rate of ∼1  s⁻¹ in the low-temperature limit.

A selective 15N-to-(1)H polarization transfer sequence for more sensitive detection of 15N-choline.

The sensitivity and information content of heteronuclear nuclear magnetic resonance is frequently optimized by transferring spin order of spectroscopic interest to the isotope of highest detection sensitivity prior to observation. This strategy is extended to 15N-choline using the scalar couplings to transfer polarization from 15N to choline's nine methyl 1H spins in high field. A theoretical analysis of a sequence using nonselective pulses shows that the optimal efficiency of this transfer is decreased by 62% as the result of competing 15N-(1)H couplings involving choline's four methylene protons.

Hyperpolarized (1)H NMR employing low gamma nucleus for spin polarization storage.

Here, we demonstrate the utility of low gamma nuclei for spin storage of hyperpolarization followed by proton detection, which theoretically can provide up to approximately (gamma[1H]/gamma[X])(2) gain in sensitivity in hyperpolarized biomedical MR. This is exemplified by hyperpolarized 1-(13)C sites of 2,2,3,3-tetrafluoropropyl 1-(13)C-propionate-d(3) (TFPP), (13)C T(1) = 67 s in D(2)O, and 1-(13)C-succinate-d(2), (13)C T(1) = 105 s in D(2)O, pH 11, using PASADENA. In a representative example, the spin polarization was stored on (13)C for 24 and 70 s, respectively, while the samples were transferred from a low magnetic field polarizer operating at 1.

Imaging quantum confinement with optical and POWER (perturbations observed with enhanced resolution) NMR.

The nanoscale distributions of electron density and electric fields in GaAs semiconductor devices are displayed with NMR experiments. The spectra are sensitive to the changes to the nuclear-spin Hamiltonian that are induced by perturbations delivered in synchrony with a line-narrowing pulse sequence. This POWER (perturbations observed with enhanced resolution) method enhanced resolution up to 10(3)-fold, revealing the distribution of perturbations over nuclear sites.

An optical NMR spectrometer for Larmor-beat detection and high-resolution POWER NMR.

Optical nuclear magnetic resonance (ONMR) is a powerful probe of electronic properties in III-V semiconductors. Larmor-beat detection (LBD) is a sensitivity optimized, time-domain NMR version of optical detection based on the Hanle effect. Combining LBD ONMR with the line-narrowing method of POWER (perturbations observed with enhanced resolution) NMR further enables atomically detailed views of local electronic features in III-Vs.

Fluorine-19 NMR chemical shift probes molecular binding to lipid membranes.

The binding of amphiphilic molecules to lipid bilayers is followed by 19F NMR using chemical shift and line shape differences between the solution and membrane-tethered states of -CF 3 and -CHF 2 groups. A chemical shift separation of 1.6 ppm combined with a high natural abundance and high sensitivity of 19F nuclei offers an advantage of using 19F NMR spectroscopy as an efficient tool for rapid time-resolved screening of pharmaceuticals for membrane binding.

PASADENA hyperpolarization of succinic acid for MRI and NMR spectroscopy.

We use the PASADENA (parahydrogen and synthesis allow dramatically enhanced nuclear alignment) method to achieve 13C polarization of approximately 20% in seconds in 1-13C-succinic-d2 acid. The high-field 13C multiplets are observed as a function of pH, and the line broadening of C1 is pronounced in the region of the pK values. The 2JCH, 3JCH, and 3JHH couplings needed for spin order transfer vary with pH and are best resolved at low pH leading to our use of pH approximately 3 for both the molecular addition of parahydrogen to 1-13C-fumaric acid-d2 and the subsequent transfer of spin order from the nascent protons to C1 of the succinic acid product.

Towards hyperpolarized (13)C-succinate imaging of brain cancer.

We describe a novel (13)C enriched precursor molecule, sodium 1-(13)C acetylenedicarboxylate, which after hydrogenation by PASADENA (Parahydrogen and Synthesis Allows Dramatically Enhanced Nuclear Alignment) under controlled experimental conditions, becomes hyperpolarized (13)C sodium succinate. Fast in vivo 3D FIESTA MR imaging demonstrated that, following carotid arterial injection, the hyperpolarized (13)C-succinate appeared in the head and cerebral circulation of normal and tumor-bearing rats. At this time, no in vivo hyperpolarized signal has been localized to normal brain or brain tumor.

Ultra-fast three dimensional imaging of hyperpolarized 13C in vivo.

Objective: PASADENA, a chemical method of enhancing nuclear spin polarization has demonstrated 13C polarizations of order unity for the nascent products of molecular addition by parahydrogen. The extreme brevity of signal enhancement obtained by hyperpolarization requires improved 13C MR in vivo imaging techniques for their optimum utility.

Materials And Methods: 13C imaging sequences, including 13C 3D FIESTA, were compiled for a GE LX 1.

Observation of force-detected nuclear magnetic resonance in a homogeneous field.

We report the experimental realization of BOOMERANG (better observation of magnetization, enhanced resolution, and no gradient), a sensitive and general method of magnetic resonance. The prototype millimeter-scale NMR spectrometer shows signal and noise levels in agreement with the design principles. We present 1H and 19F NMR in both solid and liquid samples, including time-domain Fourier transform NMR spectroscopy, multiple-pulse echoes, and heteronuclear J spectroscopy.

Quantum statistical corrections to dynamic nuclear magnetic resonance.

A quantum statistical treatment of the chemical exchange between molecular eigenstates or conformations revealed previously unsuspected dynamic terms in the spin Hamiltonian operator that describes fast exchange. These terms resulted from the effect of nuclear spin on rotational and vibrational relaxation. With the traditional theory, an interpretation of new carbon-13 nuclear magnetic resonance measurements of the chemical shift of methylcyclohexane in solution showed fast-exchange equilibrium constants that were inconsistent with the slow-exchange free-energy difference and were spread over a range of 30 percent for the various carbon-13 positions.

Nuclear magnetic resonance by measuring reaction yield of spin symmetry species.

It is proposed that the nuclear magnetic resonance of sites which release dihydrogen can be obtained by measuring the branching fraction to the ortho and para forms. The motivation is to transform the sensitivity problem from that of detecting magnetization into the more tractable one of establishing the para and ortho content of free H2. It is shown with a density operator formalism that the para mole fraction reports directly on the zero-quantum coherence of the precursor and that other spin operators may be observed indirectly.

Force-detected magnetic resonance without field gradients.

A novel method of nuclear magnetic resonance (NMR) is described which promises to be preferable to known general methods at sample length scales below approximately 100 microm. Its advantages stem from the seemingly paradoxical combination of a homogeneous static magnetic field and detection of a mechanical force between a spin-bearing sample and a magnet assembly. In contrast to other methods of force-detected nuclear magnetic resonance (FDNMR), the method is characterized by better observation of magnetization, enhanced resolution, and no gradient (BOOMERANG), and it is generally applicable with respect to sample composition, pulse sequence, and magnetic field strength.

Reduced haemolytic C1 activity in serum of hypogammaglobulinaemic chickens.

Sera from hypogammaglobulinaemic chickens, aged 22–44 days, and age-matched controls were assayed for C1 haemolytic activity by three methods, two involving cell intermediates (EAIgMC4 and EAckC4) and the third an EAck and a guinea-pig R1. Total haemolytic complement (C) was also titrated using rabbit erythrocytes bearing chicken antibody. Immunoglobulin status was monitored by immunoelectrophoresis.