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Encapsulating a protein in a reverse micelle and dissolving it in a low-viscosity solvent can lower the rotational correlation time of a protein and thereby provides a novel strategy for studying proteins in a variety of contexts. The preparation of the sample is a key element in this approach and is guided by a number of competing parameters. Here we examine the applicability of several strategies for the preparation and characterization of encapsulated proteins dissolved in low viscosity fluids that are suitable for high performance NMR spectroscopy. Ubiquitin is used as a model system to explore various issues such as the homogeneity of the encapsulation, characterization of the hydrodynamic performance of reverse micelles containing protein molecules, and the effective pH of the water environment of the reverse micelle. [ABSTRACT FROM AUTHOR]

Application of triple-resonance and isotope-edited-NOE methods to the study of increasingly larger macromolecules and their complexes remains a central goal of solution NMR spectroscopy. The slow reorientational motion of larger molecules leads to rapid transverse relaxation and results in losses in both resolution and sensitivity of multidimensional-multinuclear solution NMR experiments. A recently described technique employs a physical approach to increase the tumbling rate of macromolecules in an attempt to preserve access to the full range of structural restraints available to studies of smaller systems. This technique involves encapsulation of a hydrated protein in a surfactant shell which is subsequently solubilized in a low viscosity solvent. A simple, efficient and cost effective NMR cell that accommodates the moderate liquefaction pressures required in the encapsulation method is described. Application of the method to the 56 kD triose phosphate isomerase homodimer is demonstrated. [ABSTRACT FROM AUTHOR]

The majority of proteins are too large to be comprehensively examined by solution NMR methods, primarily because they tumble too slowly in solution. One potential approach to making the NMR relaxation properties of large proteins amenable to modern solution NMR techniques is to encapsulate them in a reverse micelle which is dissolved in a low viscosity fluid. Unfortunately, promising low viscosity fluids such as the short chain alkanes, supercritical carbon dioxide, and various halocarbon refrigerants all require the application of significant pressure to be kept liquefied at room temperature. Here we describe the design and use of a simple cost effective NMR tube suitable for the preparation of solutions of proteins encapsulated in reverse micelles dissolved in such fluids. [ABSTRACT FROM AUTHOR]