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Scientists at UC Santa Cruz need your help! They have been unable to solve the structure of the human astrovirus (HAstV) capsid protein, which is involved in host cell receptor binding. They have some experimental data about the protein structure, but have been unable to find a model that explains the experimental data. This is a multi-start puzzle, with 5 different starting structures provided by the Zhang structure prediction server. Reset the puzzle to cycle through the different starting models. We are giving you 2 weeks to try out all 5 starting models.

Design a symmetric protein trimer, with 3 identical chains of 60 residues each! This puzzle includes a Secondary Structure Objective, so no more than 50% of your design can form helices. The H-bond Network Objective encourages players to build buried, satisfied H-bond networks at the interface between symmetric chains. H-bond networks are a great way to introduce polar residues at the interface, but it's important that all of the bondable atoms make hydrogen bonds! We've also adjusted the H-bond Network Objective so that poor-scoring H-bonds may not contribute to networks; poor-scoring H-bonds will be displayed in red. This puzzle uses the Buried Unsats Objective, with a large penalty for buried polar atoms that can't make H-bonds. In this puzzle, there are no limits on the Complex Core, but we've included the Complex Core objective so players can see the core residues that can be incorporated into H-bond Networks.

Design a protein to bind to influenza virus! This puzzle is set up similar to the Round 5, but we've increased the Contact Surface goal to 500.

This is a throwback puzzle to the early days of Foldit. This human protein helps to regulate the reduction potential of the cell, and should be modeled here in reduced form (with no disulfide bonds). We are revisiting old Foldit puzzles so we can see how useful the recent additions to the game have been.

Design a D2 symmetric protein tetramer, with 4 identical chains that assemble together! Unlike the cyclical C4 symmetry that we are used to, the proteins in this puzzle will come together as a "dimer of dimers" with D2 symmetry. The H-bond Network Objective encourages players to build buried, satisfied H-bond networks at the interface between symmetric chains. H-bond networks are a great way to introduce polar residues at the interface, but it's important that all of the bondable atoms make hydrogen bonds! We've also adjusted the H-bond Network Objective so that poor-scoring H-bonds may not contribute to networks; poor-scoring H-bonds will be displayed in red. This puzzle uses the Buried Unsats Objective, with a large penalty for buried polar atoms that can't make H-bonds. In this puzzle, there are no limits on the Complex Core, but we've included the Complex Core objective so players can see the core residues that can be incorporated into H-bond Networks.

Design a protein that can bind to the TGF-beta receptor! We saw some excellent designs in the previous Round 2 puzzle, so this puzzle is set up just the same. Try to max out the Contact Surface Objective by using sidechains that pack closely against the target binding site!

Fold this TNK1 protein into the electron density map! This is a follow up to Puzzle 1984, now starting from the crystallographer's best model. We want to know if you can improve it!

Design a symmetric protein tetramer, with 4 identical chains that assemble together! This puzzle includes a Secondary Structure Objective, so no more than 50% of your design can form helices. The H-bond Network Objective encourages players to build buried, satisfied H-bond networks at the interface between symmetric chains. H-bond networks are a great way to introduce polar residues at the interface, but it's important that all of the bondable atoms make hydrogen bonds! We've also adjusted the H-bond Network Objective so that poor-scoring H-bonds may not contribute to networks; poor-scoring H-bonds will be displayed in red. This puzzle uses the Buried Unsats Objective, with a large penalty for buried polar atoms that can't make H-bonds. In this puzzle, there are no limits on the Complex Core, but we've included the Complex Core objective so players can see the core residues that can be incorporated into H-bond Networks.

This sandbox puzzle features a symmetric tetramer design by ichwilldiesennamen from Puzzle 1977. An exceptional 100% satisfied H-bond network is buried at the interface with zero BUNS! That should prevent this design from forming aggregates or off-target assemblies. For more, check out Foldit Lab Report #19 on YouTube! This sandbox puzzle is non-competitive and will not award any points.

Design a protein to bind to the Tie2 receptor! This puzzle is much like the Round 1 puzzle, except that we've increased the threshold for the Contact Surface Objective. Aim for a Contact Surface value of at least 500!