Time-resolved solid state NMR of biomolecular processes with millisecond time resolution

We review recent efforts to develop and apply an experimental approach to the structural characterization of transient intermediate states in biomolecular processes that involve large changes in molecular conformation or assembly state. This approach depends on solid state nuclear magnetic resonance (ssNMR) measurements that are performed at very low temperatures, typically 25-30 K, with signal enhancements from dynamic nuclear polarization (DNP). This approach also involves novel technology for initiating the process of interest, either by rapid mixing of two solutions or by a rapid inverse temperature jump, and for rapid freezing to trap intermediate states. Initiation by rapid mixing or an inverse temperature jump can be accomplished in approximately-one millisecond. Freezing can be accomplished in approximately 100 microseconds. Thus, millisecond time resolution can be achieved. Recent applications to the process by which the biologically essential calcium sensor protein calmodulin forms a complex with one of its target proteins and the process by which the bee venom peptide melittin converts from an unstructured monomeric state to a helical, tetrameric state after a rapid change in pH or temperature are described briefly. Future applications of millisecond time-resolved ssNMR are also discussed briefly. Published by Elsevier Inc.

Automated summary

This article reviews recent developments in the experimental approach to characterizing transient intermediate states in biomolecular processes. This approach relies on solid state nuclear magnetic resonance (ssNMR) measurements at very low temperatures, enhanced by dynamic nuclear polarization (DNP). It also involves novel technologies for initiating and freezing the process of interest quickly. Recent applications include studying the formation of a complex between calmodulin and its target protein, as well as the conversion of the bee venom peptide melittin from an unstructured monomeric state to a helical, tetrameric state. Future applications of millisecond time-resolved ssNMR are also briefly discussed.