D.J. Thomas’s research while affiliated with European Molecular Biology Laboratory and other places

... Standard motifs in protein secondary structure are traditionally described in terms of two torsional angles, φ and ψ, per residue, which define for each C α -atom the rotation of the left and right peptide plane about the N − C α and C α − C bond, respectively [187]. In the past different methods have been developed to determine secondary structure elements [106,163,57,190] and to describe their geometry in more detail [9,181,194]. A rigourous mathematical description of protein secondary structure can be obtained by applying the theory of screw motions, where the winding of the protein backbone is described in terms of local helix parameters. ...

Reference:

Signature of protein adaptation to warm deep sea environments: the case of Initiation Factor 6 studied by molecular simulation and neutron scattering.