High Pressure NMR

NMR In the early 1990s we became very interested in the application of high hydrostatic pressure to problems in protein biophysics. High pressure NMR of biomacromolecules was largely limited to the so-called autoclave design where the entire probe is put under pressure. This approach allowed very high pressures to be achieved but completely compromised the quality of the probe that could be constructed under this constraint. We implemented a high pressure tube approach that enabled NMR at kilobar pressures in a standard state-of-the-art high performance probe. The key feature was the invention of a method for joining the tube to a pressure manifold. We have used hydrostatic pressure NMR in a variety of ways over the past fifteen years. An initial result, was to take advantage of the large difference in DV associated with disruption and solvation of ion pairs (large and negative due to electrostriction) as compared to the disruption of a VDW interaction (small). This allowed us to answer a seemingly simple question: how much is an ion pair worth in free energy? (Urbauer et al. (1995) JACS). The large electrostriction effects in protein complexes also allowed the exposure of a protein-protein molecular recognition mechanism (Kranz et al. (2002) Biochemistry). Until recently, the apparatus was home built and rather cumbersome and unpredictable, which is unsettling in the context of an expensive NMR cyroprobe. Recently, our tube design has been commercialized and made much easier to use by addition of a computer controlled pressure generator and a tube with much higher pressure capabilities (please see disclosure). These advances now make use of high pressure simpler and, importantly, safe to the instruments. As a result, our use of pressure is expanding rapidly, especially in the context of hydrogen exchange and NMR relaxation studies of protein motion where we anticipate significant benefits.

Hydrogen Exchange

Walter Englander introduced the idea of native state hydrogen exchange in 1995 where the stability of an intrinsically cooperative piece of structure in a protein can be differentially modulated by chemical denaturant perturbation. The distinguishing feature is the change in accessible surface area. This led, in part, to the "foldon" view of the energy landscape of proteins. However, one can protest that the chemical denaturant

Current Project Personnel

Ellen Fu
John Gledhill

On-Going & Future Projects

  • applications to hydrogen exchange in large proteins
  • applications in high dimensional NMR spectra
  • applications in selective excitation spectroscopy

Useful papers

Gledhill & Wand (2010) JMR
Gledhill et al (2009) J Biomol. NMR
Gledhill & Wand (2008) JMR
Gledhill & Wand (2007) JMR