Rocking motion in solid proteins as studied by solid-state NMR techniques

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The aim of the project is a comparative study of a specific type of molecular dynamics in solid protein samples, overall restricted protein motion as a whole, that is rocking motion. This type of protein mobility was discovered only recently and its nature is still not fully clear. The parameters of the rocking motion, that is the amplitude, the correlation time, the width of the correlation time distribution and the activation energy, will be experimentally determined using the 15N and 13C relaxation (T1rho) and exchange (dipolar and CSA CODEX) solid-state NMR techniques that cover microsecond to millisecond ranges of molecular motions. The experiments will be conducted on two proteins, GB1 and thermophilic proteasome, having very different molecular weight. Both proteins will be studied in a form of microcrystals and amorphous powders at different hydration levels. Thermophilic proteasome will also be investigated in a form of sediment in a magic-angle-spinning rotor. Ultimately, we hope to find answers on the following questions: a) How different is the rocking motion between proteins of different size and structural features? b) What is the difference between the rocking motion of the same protein in crystalline and amorphous states and in MAS-sediments? c) How the hydration layer between proteins affects the parameters of the rocking motion? d) How wide is the correlation times distribution of the rocking motion?