Real Time Observation of Low-Temperature Protein Motions

Optical methods were used to study the internal motions of myoglobin and cytochrome c. The experiments show that these proteins exhibit conformational fluctuations at temperatures as low as 2 K. The distribution of fluctuation rates can be measured in real time and turns out to be very sharp. The temperature dependence of the structural relaxation of myoglobin follows a simple Arrhenius law. The results are in agreement with existing models for protein dynamics.