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In this paper the authors compare 400 nm one-photon and 800 nm two-photon two-dimensional Fourier transform electronic spectra of the organic laser dye Coumarin 102 in methanol using collinear optical pulse sequences and phase cycling. Results from the two different experiments show differences in the photon echo peak positions and shapes, reflecting differences in the two-photon and one-photon selection rules. [ABSTRACT FROM AUTHOR]

Artifacts arising from aperiodic turbulent spin dynamics in gradient-based nuclear magnetic resonance (NMR) applications are comprehensively surveyed and numerically simulated by a nonlinear Bloch equation. The unexpected dynamics, triggered by the joint action of radiation damping and the distant dipolar field, markedly deteriorate the performance of certain pulse sequences incorporating weak pulsed-field gradients and long evolution times. The effects are demonstrated in three general classes of gradient NMR applications: solvent signal suppression, diffusion measurements, and coherence pathway selection. Gradient-modulated solvent transverse magnetization can be partially rephased in a series of self-refocusing gradient echoes that blank out solute resonances in the CHESS (chemical-shift-selective spectroscopy) and WATERGATE (gradient-tailored water suppression) solvent suppression schemes. In addition, the discovered dynamics contribute to erratic echo attenuation in pulsed gradient spin echo (PGSE) and PGSE stimulated echo diffusion measurements and produce coherence leakage in gradient-selected DQFCOSY and HMQC experiments. Specific remedies for minimizing unwanted effects are presented. [ABSTRACT FROM AUTHOR]

Analyzes additional resonances due to dipolar couplings between distant nuclei in a variety of two-dimensional solution nuclear magnetic resonance. Use of Bloch equations having a mean-field approximation to the demagnetizing field; Link between the peaks and intermolecular multiple-quantum coherence; Prediction of intensities in solution for dipolar effects.

It was recently reported that multiple-quantum NMR coherences could apparently be observed in water and other concentrated samples, in direct violation of established theory. These results were previously explained in a dressed-state framework as manifestations of the coupling between the spins and the coil (quantized radiation damping). Here we provide details of previously communicated experimental explorations of these effects [J. Chem. Phys. 96, 1659 (1992)], and we extend these results to multicomponent samples. We observe cross peaks between independent molecules in solution in two-dimensional experiments, including spectra with multiple-quantum coherence transfer echoes; we also demonstrate coherence transfer between solvent and (dilute) solute molecules. However, we show that these intermolecular cross peaks are induced by a mechanism which is local in nature, and thus radiation damping (either classical or quantized) cannot provide the bulk of the explanation for their occurrence. Simulations and analytical results show that the dipolar demagnetizing field can account for many of these surprising effects, although a complete picture must be more complex. [ABSTRACT FROM AUTHOR]

NMR with thermal polarization requires relatively concentrated samples, particularly for nuclei with low abundance and low gyromagnetic ratios, such as 15N. We expand the substrate scope of SABRE, a recently introduced hyperpolarization method, to allow access to 15N-enriched Schiff bases. These substrates show fractional 15N polarization levels of up to 2 % while having only minimal 1H enhancements. [ABSTRACT FROM AUTHOR]

Long-lived nuclear spin states could greatly enhance the applicability of hyperpolarized nuclear magnetic resonance. Using singlet states between inequivalent spin pairs has been shown to extend the signal lifetime by more than an order of magnitude compared to the spin lattice relaxation time (T1), but they have to be prevented from evolving into other states. In the most interesting case the singlet is between chemically equivalent spins, as it can then be inherently an eigenstate. However this presents major challenges in the conversion from bulk magnetization to singlet. In the only case demonstrated so far, a reversible chemical reaction to break symmetry was required. Here we present a pulse sequence technique that interconverts between singlet spin order and bulk magnetization without breaking the symmetry of the spin system. This technique is independent of field strength and is applicable to a broad range of molecules. [ABSTRACT FROM AUTHOR]

Purpose: A review of MRI temperature imaging methods based on intermolecular multiple quantum coherences (iMQCs) is presented. Temperature imaging based on iMQCs can provide absolute temperature maps that circumvent the artefacts that other proton frequency shift techniques suffer from such as distortions to the detected temperature due to susceptibility changes and magnetic field inhomogeneities. Thermometry based on iMQCs is promising in high-fat tissues such as the breast, since it relies on the fat signal as an internal reference. This review covers the theoretical background of iMQCs, and the necessary adaptations for temperature imaging using iMQCs. Materials and methods: Data is presented from several papers on iMQC temperature imaging. These studies were done at 7T in both phantoms and in vivo. Results from phantoms of cream (homogeneous mixture of water and fat) are presented as well as in vivo temperature maps in obese mice. Results: Thermometry based on iMQCs offers the potential to provide temperature maps which are free of artefacts due to susceptibility and magnetic field inhomogeneities, and detect temperature on an absolute scale. Conclusions: The data presented in the papers reviewed highlights the promise of iMQC-based temperature imaging in fatty tissues such as the breast. The change in susceptibility of fat with temperature makes standard proton frequency shift methods (even with fat suppression) challenging and iMQC-based imaging offers an alternative approach. [ABSTRACT FROM AUTHOR]

The dependence of the bulk signal intensity from a CRAZED NMR pulse sequence on magnetic field gradient strength and direction as a method to probe the geometry of porous materials is investigated. In this article, we report on the reconstruction of three-dimensional media consisting of a void phase and an NMR-observable liquid phase using the bulk intensity of the distant dipolar field. The correlation gradient strength and direction provide the spatial encoding of the material geometry. An integral equation for the total signal intensity is then solved numerically by a simulated annealing algorithm to recover the indicator function of the fluid phase. Results show that cylindrical and spherical structures smaller than the volume contributing to the NMR signal can be resolved using three values of the correlation distance and three orthogonal gradient directions. This is done by minimizing a cost function which measures the distance between the bulk signal dependence on gradient parameters for the simulated configuration and the signal dependence for the target configuration. The algorithm can reconstruct and differentiate their spherical and cylindrical phase-inverted equivalents. It can also differentiate horizontal from vertical cylinders, demonstrating the potential for assessing structural anisotropy and other coarse geometric quantifiers in a porous material. [Copyright &y& Elsevier]

Various analogs of NMR and MRI are now technically possible in optics; specifically, high-resolution laser-pulse shaping and complex pulse sequence generation with well-defined phase shifts has been demonstrated. Here we summarize this technology and discuss the potential for these methods to enhance optical functional imaging, competing with (and surpassing?) what is possible by functional MRI. [Copyright &y& Elsevier]

Experimental investigations of the effects of moderately powerful (10-20 W cm ) offresonant continuous lasers on NMR spectra provide no evidence for the B (3) field recently proposed, or for any other mechanism which depends on the light polarization. Observed 1H and 13C line shifts with argon-ion laser irradiation for the molecule p -methoxyphenyliminocamphor mostly can be explained by heating effects. Residual shifts due to other mechanisms appear to be at most 0.1 Hz (5% of the linewidth). One mechanism which could account for residual shifts of this magnitude is differences between NMR frequencies in the excited (triplet) and ground electronic states, although our data have insufficient resolution to make definitive claims. However, it seems unlikely that this effect can be made sufficiently large to give practical resolution enhancements without massive heating. - 2. [ABSTRACT FROM AUTHOR]

Reports on the production and detection of intermolecular multiple-quantum coherences between bulk water and a glycoprotein fragment at modest concentration. Density matrix treatment; Distortion of peak intensities; Methods for contrast enhancement in magnetic resonance imaging.

Reports on the difficulties in interpreting the spectra of nuclear magnetic resonance (NMR). Problems and solutions in interpreting NMR; How it works; Methods used in developing techniques for interpretation.

We report the design and development of novel 15N-and 13C-labeled NO-sensing probes for hyperpolarized nuclear magnetic resonance (HP-NMR) studies. These probes undergo selective and rapid reaction with NO to generate the AZO-products in situ that can be monitored with distinguishable NMR signals as a read-out. This study also provides direct comparison of the 15N and 13C nuclei performances in hyperpolarized reaction-based probes. [Display omitted] [Display omitted] Nitric oxide (NO) is an important signaling molecule involved in a wide range of biological processes. Development of non-invasive, real-time detection of NO is greatly desired yet remains challenging. Here we report the design and development of novel 15N- and 13C-labeled NO-sensing probes for hyperpolarized nuclear magnetic resonance (HP-NMR) studies. These probes undergo selective and rapid reaction with NO to generate in situ AZO-products that can be monitored with distinguishable NMR signals as a read-out. This study also allows for a direct comparison of the 15N and 13C nuclei performances in hyperpolarized reaction-based probes. The simple and general SABRE-SHEATH hyperpolarization method works on the 15N- and 13C-NO-sensing probes. Measured long spin–lattice relaxation (T 1) values, especially for 15N-NO probes, will allow for real-time reaction-based imaging of NO. [ABSTRACT FROM AUTHOR]

The article presents information on the Magnetic resonance spectroscopy. Diagnostics can be empowered with the richness of Nuclear Magnetic Resonance which is familiar to the lab chemist. Intermolecular zero quantum coherences (iZQCs) are intrinsically insensitive to magnetic field inhomogeneities. Despite some variations, they yield sharp lines along the indirect dimension. This communication presents the first high-resolution iZQC spectrum in vivo which reveals that motion has restricted previous attempts. The fast spectroscopy allows the successful application of iZQC spectroscopy in vivo to organs that are inaccessible by standard techniques.

A major challenge in cancer biology is to monitor and understand cancer metabolism in vivo with the goal of improved diagnosis and perhaps therapy. Because of the complexity of biochemical pathways, tracer methods are required for detecting specific enzyme-catalyzed reactions. Stable isotopes such as 13C or 15N with detection by nuclear magnetic resonance provide the necessary information about tissue biochemistry, but the crucial metabolites are present in low concentration and therefore are beyond the detection threshold of traditional magnetic resonance methods. A solution is to improve sensitivity by a factor of 10,000 or more by temporarily redistributing the populations of nuclear spins in a magnetic field, a process termed hyperpolarization. Although this effect is short-lived, hyperpolarized molecules can be generated in an aqueous solution and infused in vivo where metabolism generates products that can be imaged. This discovery lifts the primary constraint on magnetic resonance imaging for monitoring metabolism--poor sensitivity--while preserving the advantage of biochemical information. The purpose of this report was to briefly summarize the known abnormalities in cancer metabolism, the value and limitations of current imaging methods for metabolism, and the principles of hyperpolarization. Recent preclinical applications are described. Hyperpolarization technology is still in its infancy, and current polarizer equipment and methods are suboptimal. Nevertheless, there are no fundamental barriers to rapid translation of this exciting technology to clinical research and perhaps clinical care. [ABSTRACT FROM AUTHOR]

Focuses on a study which showed that two readily observed effects in solution nuclear magnetic resonance combine to generate bizarre spin dynamics even with simple sequences. Explanation of the simplest pulse/gradient combination; Effect of radiation; Occurrence of positive feedback.