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Fold a kinesin protein into an electron density map! This is a follow-up to Puzzle 1767, now starting with the crystallographer's structure! Players may also load in their solutions from Puzzle 1767. Note that this puzzle will only be up for 5 days, and will expire on December 13.

This is the second puzzle in our poly-proline helix design series! This is an 80 residue protein with a 12-residue long frozen poly-proline helix, and designable residues on either side. Just like in Round 1, it will be necessary to satisfy the exposed oxygens on the helix backbone to ensure that the protein stays folded! Globular structures with a hydrophobic core will have the best chance of folding in the real world.

This is a throwback puzzle to the early days of Foldit. This toxin, produced by the Mozambique spitting cobra, induces contracture in skeletal and cardiac muscle. This protein contains eight cysteine residues, which oxidize to form four disulfide bonds. We are revisiting old Foldit puzzles so we can see how useful the recent additions to the game have been.

Fold a kinesin protein into an electron density map! We are giving you a monomer unit of the crystal structure 6IGN, which represents the coiled-coil stalk portion of a kinesin protein. Kinesins are motor proteins that transport cargo within the cell, by "walking" along the cellular cytoskeleton. This particular crystal structure of has a poor R-free value, meaning that some of the x-ray diffraction data is poorly explained by the crystallographer's structure. We are curious whether Foldit players can build a better structure into the electron density map!

Redesign a TIM barrel protein with symmetry! We're looking for Foldit players' help in redesigning a well-behaved monomeric protein, so that it self-assembles into a trimer with C3 symmetry. The starting structure is a large (184 residue) protein previously designed in the Baker Lab. Players should bring the three symmetric units into contact, and redesign the interface between units. We expect the monomer unit may need to change shape slightly to make a good interface, so the backbone is flexible and all positions can be redesigned. In nature, proteins with this kind of fold (called a TIM barrel) are frequently found as symmetric complexes. We'd like to see if we can turn this designed TIM barrel into a symmetric complex, but this is a difficult problem for our computer programs in the Baker Lab. We think Foldit players can help!

This is a throwback puzzle to the early days of Foldit. This protein, which inhibits muscle contraction in the absence of calcium ions, changes conformation in the presence of calcium to allow muscle contraction. We are revisiting old Foldit puzzles so we can see how useful the recent additions to the game have been.

H-bond Networks are back! The H-bond Network Objective encourages players to bury 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! In this puzzle, there are no limits on the Complex Core, but we've included the Complex Core objective so players can see which residues count as core in the H-bond Networks.

This puzzle introduces a new secondary structure, the poly-proline helix! The starting structure is a small 38 residue protein with a frozen helix and designable residues on either end. Players should fold the starting structure to create a compact globular protein that incorporates this new type of secondary structure. Note that the backbone of the poly-proline helix has bondable oxygen atoms. If any of these oxygens are buried in the protein core, they will need to make hydrogen bonds! See the blog for more information!

This is a throwback puzzle to the early days of Foldit. This toxin is found in green mamba venom, and blocks the flow of calcium ions that normally depolarize the muscle cell to induce muscle contraction. This protein contains six cysteine residues that oxidize to form three disulfide bonds. We are revisiting old Foldit puzzles so we can see how useful the recent additions to the game have been.

H-bond Networks are back! The H-bond Network Objective encourages players to bury 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! In this puzzle, there are no limits on the Complex Core, but we've included the Complex Core objective so players can see which residues count as core in the H-bond Networks. There a few other objectives in effect; see the puzzle comments for details. The Baker Lab will run folding predictions on your solutions for this puzzle, and those that perform well will be synthesized in the lab. Remember, you can use the Upload for Scientists button for up to 5 designs that you want us to look at, even if they are not the best-scoring solutions!