Clashing Importance or CI is a Foldit setting that controls how strongly clashes between atoms push the protein apart. Clashing importance varies between 0.0 and 1.0. At CI = 0.0, Foldit is content to let two atoms occupy the same space at the same time. At CI = 1.0, atoms are pushed apart when they even start to get close to each other. CI = 1.0 represents the "real world" importance of clashes.Clashing importance can be controlled manually using the slider in the Behavior Options menu.
Clashing importance can also be set in recipes.
Setting clashing importance to less than 1.0 can be a useful strategy at many points in the game. But clashes still affect the score, regardless of clashing importance. So it's important to always finish with CI = 1.0.
Programming interface Edit
The section below discusses an early verion of the behavior options menu. The technical aspects of clashing importance are still valid, but the wiggle and shake accuracy sliders are probably gone for good.
The Clashing Importance (CI) slider is a behavioral sliding scale that ranges from 0.00 to 1.00, in individual increments of 0.01. The purpose of this scale is to adjust the amount of clashing behavior tolerated by the protein by reducing the effect the van der waals and electrostatic interactions during a Pose-altering operation (e.g. Wiggle, Shake, Mutate).
Of the two remaining sliders: One slider affects the behavior of Wiggle and the other affects the behavior of Shake. The names are temporary, so if you think the names don't quite fit, we're willing to rename them.
The clashing importance behavioral slider is a strategic tool - involved in everything from programming recipes, in LUA, to bounding across multiple energy landscapes to avoid Local Minima. The importance of this valuable tool cannot be overstated.
Update - In early 2012, both the Wiggle Accuracy and Shake Accuracy Sliders were removed as developers reverted back to an earlier version. There is no projected date for their return as of March 2012.