A Range of Capabilities Available to User Community

1. SOLID STATE NMR

— NMR in Resistive (25 T) and Hybrid (45 T) Magnets
The 25 T resistive magnet has a short term temporal stability of ~5ppm and its field inhomogeneity can be reduced below 1ppm using small sample magic-angle spinning. Using the newly developed HENPEC method, residual magnetic field fluctuations can be corrected. Thus 25 T and 45 T magnets can be used for NMR experiments with medium resolution. We can use the fast 50 kHz, 2 mm MAS probe for NMR measurement of any nuclei in the lower-gamma range. A second 2 mm fast MAS probe is available for higher frequency nuclei. A 1H/2H HRMAS solution probe will be built in 2003 to extend the NMR capability of resistive magnets to solution samples and high frequency nuclei. A new Tecmag Discovery NMR console is available for NMR work on the 45 T Hybrid, the 25 T Keck, and the other resistive magnets. This instrument has three RF transmit channels, two independent receive channels, and three gradient channels. With a frequency range to 1.92 GHz, it is capable of 1H NMR up to 45 T. A flux stabilization system, ferromagnetic and active shims are being improved and optimized for 25 T system.
Fig. 1: The 27Al spectra of 9Al2O3+2B2O3 obtained at different fields, including one from 45 Tesla hybrid magnet.

— Intermolecular zero-quantum NMR spectroscopy
Warren Warren (Princeton Univ.) has been improving the intermolecular zero-quantum approach to obtain high resolution NMR spectra using the 25 T Keck resistive magnet at the NHMFL since first demonstration couple of years ago.

— Double rotation (DOR) NMR experiments
The double axial (6 kHz and 1.5 kHz for inner and outer rotations) MAS experiment averages both the first and the second-order spin interactions for high resolution NMR spectroscopy of quadrupolar nuclei. This DOR facility is available to users of the 25 T Keck, 720 MHz NB and 600 MHz WB magnets.

— Satellite-Transition Magic-Angle Spinning (STMAS)
The newly developed STMAS NMR experiment achieves high resolution isotropic NMR spectra of quadrupolar nuclei. The experiment improves spectral sensitivity by an order of magnitude over the well-known multiple-quantum MAS experiment.

— Triple-resonance solid state NMR Experiments
1H/19F/X and 1H/X/Y three-channel probes are available on the 600 MHz wide bore magnet. Triple-resonance capability permits distance measurement among nuclei with different resonance frequencies.

— High Field Structural Studies of Membrane Proteins
Double resonance spectroscopy up to 14 T for the observation of orientational constraints in membrane proteins is available. A structural approach for high-resolution structures of membrane proteins is of major scientific and medical importance.

— Stray Field Imaging
A STRAFI imaging probe has been built for the 19.6 T superconducting magnet at the NHMFL in collaboration with Andrei Samoilenko (Chemical Physics Institute, Russian Academy of Sciences). The magnet has a stray field gradient about 75 T/m at 11.7 T and the STRAFI probe can achieve spatial resolution on the order of 10 µm. A second STRAFI probe with a floating probe head (a version of goniometer) has been completed, and enhances the spatial resolution.

2. SOLUTION NMR

— Solution NMR at High Fields
A large variety if solution NMR experiments are available to users at 500, 600, 720 and 750 MHz fields. Cryoprobes are being purchased for both 500 and 600 MHz solution NMR spectrometers. These probes will be used for high throughput structural genomics and for the characterization of high sensitivity kinetic and folding processes.
Fig. 2: Expansion of contour plot from a 720 MHz 2D [15N,1H]-TROSY spectrum showing the well-resolved crosspeaks. Solution: 1 mM 15N-labeled Arginine Kinase, 5 mM Na-citrate (pH=6), [90:10] [H2O;D2O], 30°C. NMR parameters: t1max=72 ms; t2max=49 ms; measurement time=6 hr. Final matrix processed to 1.2 and 0.5 Hz/pt res­olution in 1H and 15N dimensions, respectively.

— Microcoils for Solution NMR
In collaboration with Andrew Webb (Univ. of Illinois at Champaign-Urbana), the NHMFL has been developing microcoil technology in both Tallahassee and in Gainesville using the 830 and 750 MHz instruments. This technology minimizes the amount of protein required for structural characterization.

3. IMAGING

— Microimaging Experiments
A 25 mm clear access microimaging probe body is available for use with the 500, 600 and 750 MHz microimaging spectrometers. The clear access to the active volume is essential for some small animal and flow measurements.

— Phased Array Hardware
Both the 4.7 T, 33 cm and 11.7 T, 40 cm have four channel phased array hardware installed (the first in the U.S. on animal imaging systems). A large number of in-house custom built coils are available. The brand new Siemens 3 T/60 cm head magnet is fully operational and is available for human head MRI on research subjects and for larger animal studies.

— Imaging RF Coil Development
Novel, more efficient volume imaging coils (the ReCav coils) have been developed in-house and introduced to users of 400 and 200 MHz spectrometers by RF group in Gainesville. Phased array coils have been constructed for 200 MHz.

— Hyperpolarized 129Xe and 3He
New spin exchange optical pumping system for the generation of hyperpolarized 129Xe and 3He is now available. The new polarized noble gas generator incorporates the highest power fiber coupled diode array laser system ever used for spin exchange optical pumping. The system has been designed to be self-contained for maximum functionality and portability to support a wide variety of hyperpolarized 129Xe and 3He NMR and MRI experiments at NHMFL sites. NMR applications already underway include studies of surfaces, binding sites in proteins, phase transitions, and gas clathrate hydrates.