This puzzle is unlike anything we have ever posted before! We have given you extremely accurate electron density, but no sequence information. This protein has 95-residues, but your starting model only has 5 Alanines that are floating in the density. You'll need to insert residues and mutate them as you make your way through the density. We know this won't be easy, some might even suggest that this task is impossible... but we know that if anyone can do it: you can!
We are giving you two weeks to work on this... good luck!
Most of these electron density maps are derived from protein crystals, in which a protein forms a regular lattice—you can imagine many copies of this protein aligning and arranging themselves into a 3D grid. We only visualize one "unit cell" of the crystal in the puzzle, but the density actually repeats itself infinitely in the X, Y, and Z directions.
I found this explanation with pictures helped me to understand the positioning but this is one example and unlikely to be the same for every cloud we get.
my understanding is that the cloud and associated density score and pull on the protein, continues to repeat but is only visible in the central space so building 'outside of the visible cloud' can mess you up a bit - that could be incorrect of course, but now I just build inside the cloud and turn the view off and on frequently.