Structures of Alpha-1 obtained by ab initio modelling against 2 Å resolution data. (a) Stereoview of a ball-and-stick representation of an optimized model after the initial condensation using 1000 steps of conditional dynamics using the MLF target function; (b) Cα trace of 17 models obtained after 25 cycles of optimization (black lines) with the Cα trace of the refined structure overlaid (grey lines); (c) stereoview of the Cα trace of the model with the highest σA value. From left to right the helices are oriented down, up, down and up in the refined structure (the position of the N-terminus is indicated by a ball). The chain directionality in the depicted model is therefore from left to right: incorrect, incorrect, correct and correct. Assignment of atom labels (for b and c) was based on the gradient contributions in Conditional Optimization (as described in the main text for automated model building).