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Structure determination of a small protein through a 23-dimensional molecular-replacement search

Acta Cryst. (2003). D59, 709–718


We have recently described a multidimensional molecular-replacement method that attempts to simultaneously and independently determine the positional and orientational parameters of all molecules present in the asymmetric unit of a target crystal structure through a reverse Monte Carlo optimisation of a suitable statistic (like the R factor or the linear correlation coefficient between the observed and calculated structure factor amplitudes). This paper reports the successful application of this method to a 23-dimensional molecular-replacement problem, allowing the determination of the crystal structure of a 4-α-helical bundle protein. The search model for the calculation was a 26-residue-long polyalanine helix amounting to less than 13% of the total number of atoms in the asymmetric unit of the target crystal structure.

N. M. Glykos and M. Kokkinidis