Protein dynamics

Theoretical works

Microsecond Timescale Proton Rotating-frame Relaxation under Magic Angle Spinning

Petra Rovó, Rasmus Linser

This paper deals with the theoretical foundation of proton magic-angle-spinning rotating-frame relaxation (R1r) and establishes the range of validity and accuracy of the presented approach to describe low-amplitude microsecond timescale motion in the solid-state. Beside heteronuclear dipolar and chemical shift anisotropy interactions, a major source of relaxation for protons is the homonuclear dipolar interaction. For this latter relaxation process no general analytical equation has been published until now which would describe the R1r relaxation at any spinning-speed, spin-lock field, or tilt-angle. To validate the derived equations we compared the analytical relaxation rates, obtained by solving the master equation within the framework of Redfield theory, with numerically simulated relaxation rates. We found that for small opening angles (~10°) the relaxation rates obtained with stochastic Liouville simulations agree well with the analytical Redfield relaxation rates for a large range of motional correlation times. However, deviations around the rotary-resonance conditions highlight the fact that Redfield treatment of the solid-state relaxation rates can only provide qualitative insights into the microsecond timescale motion.

doi: 10.1021/acs.jpcb.7b03333


Microsecond timescale protein dynamics: a combined solid-state NMR approach

Petra Rovó, Rasmus Linser

Conformational exchange in proteins is a major determinant in protein functionality. In particular, the microsecond to millisecond timescale is associated with enzymatic activity and interactions between biological molecules. We show here that a comprehensive data set of R1r relaxation dispersion profiles employing multiple effective fields and tilt angles can be easily obtained in perdeuterated, partly back-exchanged proteins at fast magic-angle spinning and further complemented with chemical-exchange saturation transfer NMR experiments. The approach exploits complementary sources of information and enables the extraction of multiple exchange parameters for microsecond to millisecond timescale conformational exchange, most notably including the sign of the chemical shift differences between the ground and excited states.