The angle, Θij, between the two helices, i and j, forming an EF hand of apoCaM (or holoCaM) in different states (M1, M2 and M3) at [KCl] = 0.5 M.

The direction of an α-helix, i, is defined by a vector pointing from an averaged position of the first four residues (N) to an averaged position of the last four residues in an α-helix. Θij of an EF hand is defined by the arccosine of the inner product of the two vectors of helices i and j. The notation of ABCDEFGH represents the eight helices of CaM from its N-terminus to C-terminus.