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. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1007/s10858-018-0176-3) contains supplementary material, which is available to authorized users.