Efficient analysis of macromolecular rotational diffusion from heteronuclear relaxation data

A novel program has been developed for the interpretation of N-15 relaxatio n rates in terms of macromolecular anisotropic rotational diffusion. The pr ogram is based on a highly efficient simulated annealing/minimization algor ithm, designed specifically to search the parametric space described by the isotropic, axially symmetric and fully anisotropic rotational diffusion te nsor models. The high efficiency of this algorithm allows extensive noise-b ased Monte Carlo error analysis. Relevant statistical tests are systematica lly applied to provide confidence limits for the proposed tensorial models. The program is illustrated here using the example of the cytochrome c' fro m Rhodobacter capsulatus, a four-helix bundle heme protein, for which data at three different field strengths were independently analysed and compared .