CheShift

CheShift-2 (pronounced /tʃeʃɪft/) is an application created to compute ¹³C^α and ¹³C^β protein chemical shifts and to validate protein structures. It is based on quantum mechanics computations of ¹³C^α and ¹³C^βchemical shift as a function of the torsional angles (φ, ψ, ω and χ¹, χ²) of the 20 amino acids.

CheShift-2 can return a list of theoretical chemical shift values from a PDB file. It also can display a 3D protein model based on an uploaded PDB file and chemical shift values. The 3D protein model is colored using a five color code indicating the differences of the theoretical vs the observed chemical shifts values. The differences between observed and predicted ¹³C^α and ¹³C^β chemical shifts can be used as a sensitive probe with which to detect possible local flaws in protein structures. If both ¹³C^α and ¹³C^β observed chemical shifts are provided CheShift-2 will attempt to provide a list of alternative χ1 and χ2 side-chain torsional angles that will reduce the differences between observed and computed chemical shifts, these values can be used to repair flaws in protein structures.

CheShift-2 can be accessed online at http://www.cheshift.com, or via PyMOL plugin.