Protein dynamics from Mössbauer spectra. The temperature dependence

Protein-specific dynamics reveals itself in Mössbauer spectra by a strong temperature dependence of the mean square displacement, 〈x²〉^γ, of the Mössbauer nucleus. In addition, the protein dynamics may give rise to broad lines whose width and intensity also strongly depend on temperature. Both features are understood with an extension of the Brownian oscillator model which accounts for fluctuations between conformational substates mediated by transition states. The model is also capable of relating the temperature dependence of 〈x²〉 values obtained from X-ray investigations and Mössbauer experiments. 〈x²〉 values from Mössbauer experiments exhibit saturation at high temperatures.