Abstract
Simple and convenient method of protein dynamics evaluation from the insufficient experimental N-15 relaxation data is presented basing on the ratios, products, and differences of longitudinal and transverse N-15 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.