Probing exchange kinetics and atomic resolution dynamics in high-molecular-weight complexes using dark-state exchange saturation transfer NMR spectroscopy.
We present the protocol for the measurement and analysis of dark-state exchange saturation transfer (DEST), a novel solution NMR method for characterizing, at atomic resolution, the interaction between an NMR-'visible' free species and an NMR-'invisible' species transiently bound to a very high-molecular-weight (>1 MDa) macromolecular entity. The reduced rate of reorientational motion in the bound state that precludes characterization by traditional NMR methods permits the observation of DEST. (15)N-DEST profiles are measured on a sample comprising the dark state in exchange with an NMR-visible species; in addition, the difference (ΔR(2)) in (15)N transverse relaxation rates between this sample and a control sample comprising only the NMR-visible species is also obtained. The (15)N-DEST and ΔR(2) data for all residues are then fitted simultaneously to the McConnell equations for various exchange models describing the residue-specific dynamics in the bound state(s) and the interconversion rate constants. Although the length of the experiments depends strongly on sample conditions, approximately 1 week of NMR spectrometer time was sufficient for full characterization of samples of amyloid-β (Aβ) at concentrations of ~100 μM.
Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, Bethesda, Maryland, USA.
Nicolas L
NL
Fawzi
Jinfa
J
Ying
Dennis A
DA
Torchia
G Marius
GM
Clore
D016229:Amyloid beta-Peptides / Q000737:chemistry; D007700:Kinetics; D046911:Macromolecular Substances / Q000737:chemistry*; D008970:Molecular Weight; D009587:Nitrogen Isotopes; D019906:Nuclear Magnetic Resonance, Biomolecular / Q000379:methods*; D012984:Software; D013997:Time Factors
D016229:Amyloid beta-Peptides; D046911:Macromolecular Substances; D009587:Nitrogen Isotopes