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A new method for magnetic resonance imaging (MRI) based on the detection of relatively strong signal from intermolecular zero-quantum coherences (iZQCs) is reported. Such a signal would not be observable in the conventional framework of magnetic resonance; it originates in long-range dipolar couplings (10 micrometers to 1 millimeter) that are traditionally ignored. Unlike conventional MRI, where image contrast is based on variations in spin density and relaxation times (often with injected contrast agents), contrast with iZQC images comes from variations in the susceptibility over a distance dictated by gradient strength. Phantom and in vivo (rat brain) data confirm that iZQC images give contrast enhancement. This contrast might be useful in the detection of small tumors, in that susceptibility correlates with oxygen concentration and in functional MRI., Contrast in MRI is largely based on variations in spin density or relaxation times, sometimes enhanced by injected contrast agents such as gadolinium compounds. The relation between these parameters and [...]

Researchers interested in high-resolution nuclear magnetic resonance (NMR) spectroscopy have long sought higher magnetic fields to enhance resolution and simplify spectra. Magnets with substantially larger fields than those available in the best commercial spectrometers are available, but the inhomogeneity is unacceptable for high-resolution spectra. A detection method (termed HOMOGENIZED) is presented that removes inhomogeneity while retaining chemical shift differences and J couplings. With existing inhomogeneous magnets, this method could nearly double the largest resonance frequency available for high-resolution NMR. The HOMOGENIZED sequence is based on observations of intermolecular zero-quantum coherences between a solute molecule and solvent molecules that are micrometers away; as long as the field is homogeneous over this short distance, sharp resonances are recovered without echoes. Experimental demonstrations and a detailed density matrix theory to explain the effect are presented., For decades, spectroscopists studying high-resolution NMR have sought ever higher magnetic fields, largely because the spectral width (dominated by chemical shifts) is linearly proportional to the field strength and the [...]

Experiments were carried out to examine the creation and detection of intermolecular multiple-quantum coherences between water molecules. Specifically, the influence of variable-angle pulsed field gradients and the magnetization caused by the intermolecular MQ coherences was investigated with respect to poor water suppression in biomolecular NMR studies of isotopically labeled proteins in aqueous solution.

A magnetic resonance imaging technique based on intermolecular multiple-quantum coherences in solution (the correlated spectroscopy revamped by asymmetric z gradient echo detection or CRAZED experiment) is described here. Correlations between spins in different molecules were detected by magnetic-field gradient pulses. In order for a correlation to yield an observable signal, the separation between the two spins must be within a narrow band that depends on the area of the gradient pulses. The separation can be tuned from less than 10 micrometers to more than 1 millimeter, a convenient range for many applications., A variety of nuclear magnetic resonance (NMR) methods have proven useful for extracting structural information. For example, the nuclear Overhauser effect (NEO) (1) can be used to determine if two [...]

Intermolecular multiple-quantum coherences between bulk water and a glycoprotein fragment at modest concentration (20 mM) have been experimentally produced and detected, although such coherences are inconceivable in the normal theoretical framework of nuclear magnetic resonance. A density matrix treatment explains these results by including the long-range dipolar interaction between spins and by discarding the high-temperature approximation. These results imply that peak intensities (critical for structural determinations) can be distorted in many gradient experiments, and show that magic-angle gradients provide substantial improvements with reduced gradient strengths. They also suggest methods for contrast enhancement in magnetic resonance imaging., Nuclear magnetic resonance (NMR) is an extremely versatile form of spectroscopy, in part because commercially available spectrometers can generate exceedingly complex pulse sequences. More importantly, however, quite sophisticated theoretical tools [...]