The Slow Tumbling Problem: via T2 relaxation Molecular motion can be described by:
Limits are imposed by NMR relaxation on... 
In the absence of unrestricted internal motion as tm increases T2 will decrease.
The consequence of this is physical property is transfer efficiency degrades with increasing transverse relaxation
Thus there is a practical limit on the size of proteins that can be easily studied by NMR spectroscopy.
However, there is a solution...
The Reverse Micelle:
The idea is simple. Encapsulate the soluble protein of interest within the protective water core of a reverse micelle and dissolve the resulting particle in a solvent of very low viscosity such that the entire particle would tumble faster than the isolated protein does in water.
Reverse micelles are nanoparticles consisting of a pool of water surrounded by surfactants solubilized in a low viscosity solvent.
With careful selection of conditions the proteins or other macromolecules will spontaneously encapsulate in the reverse micelle. The macr omolecules have been shown to maintain the same structural specificity as in bulk aqueous solution.
Solubilizing the entire reverse micelle particle in a low viscosity solvent such as liquid ethane can make the entire particle tumble faster than the macromolecule would tumble by itself in bulk aqueous solution. This serves to lessen the problem that has plagued NMR spectroscopy in that the larger the protein the wose the experimental performance. Thus larger molecules can be studied at high resolution without losing critical data that can be lost by deuteration.
High Pressure NMR:
We have developed a specialized high pressure NMR cell for use with the reverse micelle method. The guiding design principle was to make a cell that would work with NMR equipment available in most NMR facilities. Thus we based our cell on the 5 mm tube O.D. making it possible to use the cell with the modern cryo-probes. The volume of the high pressure tube is around two-thirds that of a typical glass tube. This provides for high sensitivity in a tube capable of pressures up to 500 bar. This pressure is more than sufficient for reverse micelle work as well as other applications that might use supercritical carbon dioxide or zenon.
Journal Articles:
Listed below are references to articles pertaining to the reverse micelle technology and the high pressure apparatus from members of Daedalus. Valentine, Kathleen G., Pometun, Maxim S., Kielec, Joseph M., Baigelman, Robert E., Staub, Jayme K., Owens, Kristy L., Wand, A. Joshua. Magnetic Susceptibility-Induced Alignment of Proteins in Reverse Micelles. Journal of the American Chemical Society (2006), 128: 15930-15931. Pometun, Maxim S., Peterson, Ronald W., Babu, Charles R., and Wand, A.Joshua. Cold denaturation of encapsulated ubiquitin. Journal of the American Chemical Society (2006), 128: 10652-10653. Peterson, Ronald W., Pometun, Maxim S., Shi, Zhengshuang, Wand, A. Joshua. Novel surfactant mixtures for NMR spectroscopy of encapsulated proteins dissolved in low-viscosity fluids. Protein Science (2005), 14(11), 2919-2921. Peterson, Ronald W., Wand, A. Joshua. Self-contained high-pressure cell, apparatus, and procedure for the preparation of encapsulated proteins dissolved in low viscosity fluids for nuclear magnetic resonance spectroscopy. Review of Scientific Instruments (2005), 76(9), 094101/1-094101/7. Shi, Zhengshuang, Peterson, Ronald W., Wand, A. Joshua. New Reverse Micelle Surfactant Systems Optimized for High-Resolution NMR Spectroscopy of Encapsulated Proteins. Langmuir (2005), 21(23), 10632-10637. Peterson, Ronald W., Lefebvre, Brian G., Wand, A. Joshua. High-Resolution NMR Studies of Encapsulated Proteins in Liquid Ethane. Journal of the American Chemical Society (2005), 127(29), 10176-10177. Lefebvre, Brian G., Liu, Weixia, Peterson, Ronald W., Valentine, Kathleen G., Wand, A. Joshua. NMR spectroscopy of proteins encapsulated in a positively charged surfactant. Journal of Magnetic Resonance (2005), 175(1), 158-162. Peterson, Ronald W., Anbalagan, Karthik, Tommos, Cecilia, Wand, A. Joshua. Forced Folding and Structural Analysis of Metastable Proteins. Journal of the American Chemical Society (2004), 126(31), 9498-9499. Babu, Charles R., Hilser, Vincent J., Wand, A. Joshua. Direct access to the cooperative substructure of proteins and the protein ensemble via cold denaturation. Nature Structural & Molecular Biology (2004), 11(4), 352-357. Wand, A. Joshua, Babu, Charles R., Flynn, Peter F., Milton, Mark J. NMR spectroscopy of encapsulated proteins dissolved in low viscosity fluids. Biological Magnetic Resonance (2003), 20(Protein NMR for the Millennium), 121-160. Babu, Charles R., Flynn, Peter F., Wand, A. Joshua. Preparation, characterization, and NMR spectroscopy of encapsulated proteins dissolved in low viscosity fluids. Journal of Biomolecular NMR (2003), 25(4), 313-323. Flynn, Peter F., Flynn, Peter F., Wand, A. Joshua. High-resolution nuclear magnetic resonance of encapsulated proteins dissolved in low viscosity fluids. Methods in Enzymology (2001), 339(Nuclear Magnetic Resonance of Biological Macromolecules, Part B), 54-70. Babu, Charles R., Flynn, Peter F., Wand, A. Joshua. Validation of Protein Structure from Preparations of Encapsulated Proteins Dissolved in Low Viscosity Fluids. Journal of the American Chemical Society (2001), 123(11), 2691-2692. Flynn, Peter F., Mattiello, Debra L., Hill, Howard D. W., Wand, A. Joshua. Optimal Use of Cryogenic Probe Technology in NMR Studies of Proteins. Journal of the American Chemical Society (2000), 122(19), 4823-4824. Ehrhardt, Mark R., Flynn, Peter F., Wand, A. Joshua. Preparation of encapsulated proteins dissolved in low viscosity fluids. Journal of Biomolecular NMR (1999), 14(1), 75-78. Wand, A. Joshua, Ehrhardt, Mark R., Flynn, Peter F. High-resolution NMR of encapsulated proteins dissolved in low-viscosity fluids. Proceedings of the
