Figure 7.

Electron density maps for a loop region of human hnRNP A1 comprising residues 141–143 (all maps σ_A weighted and contoured at 1.0 σ). In all cases, the final refined structure is shown in black. (a) Best model (shown in red) from five simulated annealing refinements using the least-squares target. The connected density in the region of the model and the broken density in the region of the correct solution is due to model bias. (b) Model (shown in blue) from conjugate gradient minimization using the maximum likelihood target. Reduced model bias due to the maximum likelihood target results in connected electron density in the region of the correct solution. (c) Representative model (shown in orange) from five simulated annealing refinements using the maximum likelihood target. The combination of torsion angle simulated annealing and the maximum likelihood target reduces model bias even further. (d) Best model (shown in green) from five simulated annealing refinements using the maximum likelihood target. The correct placement of the residues has been automatically achieved. These images were created with the program o (31).