The introduction of the multidimensional NMR spectroscopy was a breakthrough in biological NMR me-thodology since it allowed the unequivocal correlation of different spin states of the system. The introduction of large pressure perturbations in the corresponding radio frequency (RF) pulse sequences adds an extra structural dimension into these experiments. We have developed a microprocessor controlled pressure jump unit that is able to introduce fast, strong pressure changes at any point in the pulse sequences. Repetitive pressure changes of 80 MPa in the sample tube are thus feasible in less than 30 ms. Two general forms of these experiments are proposed here, the pressure perturbation transient state spectroscopy (PPTSS) and the pressure perturbation state correlation spectroscopy (PPSCS). PPTSS can be used to measure the rate constants and the activation energies and activation volumes for the transition between different conformational states including the folded and unfolded state of proteins, for polymerisation-depolymerisation processes and for ligand binding at atomic resolution. PPSCS spectroscopy correlates the NMR parameters of different pressure induced states of the system thus allowing the measurement of properties of a given pressure induced state such as a folding intermediate in a different state e. g. the folded state. Selected examples for PPTSS and PPSCS spectroscopy are presented in this paper.DOI
Journal: Journal of the American Chemical Society
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