Nuclear magnetic resonance spectroscopy is a powerful tool for the structural analysis of organic compounds and biomolecules but typically requires macroscopic sample quantities. We use a sensor, which consists of two quantum bits corresponding to an electronic spin and an ancillary nuclear spin, to demonstrate room temperature magnetic resonance detection and spectroscopy of multiple nuclear species within individual ubiquitin proteins attached to the diamond surface. Using quantum logic to improve readout fidelity and a surface-treatment technique to extend the spin coherence time of shallow nitrogen-vacancy centers, we demonstrate magnetic field sensitivity sufficient to detect individual proton spins within 1 second of integration. This gain in sensitivity enables high-confidence detection of individual proteins and allows us to observe spectral features that reveal information about their chemical composition.

http://science.sciencemag.org/content/sci/351/6275/836.full.pdf

Nuclear magnetic resonance detection and spectroscopy of single proteins using quantum logic

NMR imaging methods are provided for determining the spatial petrophysical properties of materials. These methods employ the generation of separate Mo, T1 and T2 images from which various petrophysical characteristics may be obtained, such as free fluid index, porosity, pore sizes and distributions, capillary pressure, permeability, formation factor and clay content.

NMR imaging of materials

In this article, both sodium magnetic resonance (MR) and T1ρ relaxation mapping aimed at measuring molecular changes in cartilage for the diagnostic imaging of osteoarthritis are reviewed. First, an introduction to structure of cartilage, its degeneration in osteoarthritis (OA) and an outline of diagnostic imaging methods in quantifying molecular changes and early diagnostic aspects of cartilage degeneration are described. The sodium MRI section begins with a brief overview of the theory of sodium NMR of biological tissues and is followed by a section on multiple quantum filters that can be used to quantify both bi-exponential relaxation and residual quadrupolar interaction. Specifically, (i) the rationale behind the use of sodium MRI in quantifying proteoglycan (PG) changes, (ii) validation studies using biochemical assays, (iii) studies on human OA specimens, (iv) results on animal models and (v) clinical imaging protocols are reviewed. Results demonstrating the feasibility of quantifying PG in OA patients and comparison with that in healthy subjects are also presented. The section concludes with the discussion of advantages and potential issues with sodium MRI and the impact of new technological advancements (e.g. ultra-high field scanners and parallel imaging methods). In the theory section on T1ρ, a brief description of (i) principles of measuring T1ρ relaxation, (ii) pulse sequences for computing T1ρ relaxation maps, (iii) issues regarding radio frequency power deposition, (iv) mechanisms that contribute to T1ρ in biological tissues and (v) effects of exchange and dipolar interaction on T1ρ dispersion are discussed. Correlation of T1ρ relaxation rate with macromolecular content and biomechanical properties in cartilage specimens subjected to trypsin and cytokine-induced glycosaminoglycan depletion and validation against biochemical assay and histopathology are presented. Experimental T1ρ data from osteoarthritic specimens, animal models, healthy human subjects and as well from osteoarthritic patients are provided. The current status of T1ρ relaxation mapping of cartilage and future directions is also discussed. Copyright © 2006 John Wiley & Sons, Ltd.

Sodium and T1ρ MRI for molecular and diagnostic imaging of articular cartilage

Solid-State Li NMR with Applications to the Translational Dynamics in Ion Conductors

Publisher Summary Mossbauer spectroscopy can be likened to ultraviolet spectroscopy. Both techniques employ a source of radiation, an absorber and a detector. In Mossbauer spectroscopy, we consider transitions between nuclear energy levels with the emission and absorption of y rays; whereas, in ultraviolet spectroscopy, we consider the transitions between electronic energy levels with the emission and absorption of ultraviolet radiation. To observe resonance, a range of source photon energies is scanned: in ultraviolet by the use of a prism or grating, and in Mossbauer by employing the Doppler effect. The energy of the y ray (E,) is varied by the well-known Doppler formula d E = (V/C)E, where AE = change in energy of y photon, 11 = velocity of source relative to the absorber, and c = velocity of light. As in ultraviolet, absorption is plotted versus the energy of source photon (usually in velocity units for Mossbauer). Different compounds of one isotope give different spectra— that is, the nuclear energy levels are sensitive to the extranuclear environment. These differences in spectra can be attributed to the hyperfine interactions; the interactions between the nuclear charge distribution, and the extranuclear electric and magnetic fields. These hyperfine interactions give rise to the isomer shift (IS.) , the quadrupole splitting (Q.S.), and the magnetic Zeeman splitting.

D. J. E. Ingram

Papers

Nuclear Quadrupole Resonance Spectroscopy