Fast evaluation of protein dynamics from deficient 15 N relaxation data.

Simple and convenient method of protein dynamics evaluation from the insufficient experimental ¹⁵ N relaxation data is presented basing on the ratios, products, and differences of longitudinal and transverse ¹⁵ N relaxation rates obtained at a single magnetic field. Firstly, the proposed approach allows evaluating overall tumbling correlation time (nanosecond time scale). Next, local parameters of the model-free approach characterizing local mobility of backbone amide N-H vectors on two different time scales, S ² and R _ex , can be elucidated. The generalized order parameter, S ² , describes motions on the time scale faster than the overall tumbling correlation time (pico- to nanoseconds), while the chemical exchange term, R _ex , identifies processes slower than the overall tumbling correlation time (micro- to milliseconds). Advantages and disadvantages of different methods of data handling are thoroughly discussed.