Related Experiment Video
Updated: May 26, 2026

Magnetic Tweezers for the Measurement of Twist and Torque
Published on: May 19, 2014
Optimized torsion-angle normal modes reproduce conformational changes more accurately than cartesian modes
Jenelle K Bray1, Dahlia R Weiss, Michael Levitt
1Department of Structural Biology, Stanford Medical School, Stanford, California, USA. jenelle@stanford.edu
Abstract:
We present what to our knowledge is a new method of optimized torsion-angle normal-mode analysis, in which the normal modes move along curved paths in Cartesian space. We show that optimized torsion-angle normal modes reproduce protein conformational changes more accurately than Cartesian normal modes. We also show that orthogonalizing the displacement vectors from torsion-angle normal-mode analysis and projecting them as straight lines in Cartesian space does not lead to better performance than Cartesian normal modes. Clearly, protein motion is more naturally described by curved paths in Cartesian space.
Related Concept Videos
Conformations of Cyclohexane
The chair form is the most stable and derives its name from its resemblance to the “easy chair.” In the chair conformation, two carbon atoms are arranged out-of-plane — one above and one below, minimizing the torsional strain. In the chair form, the bond angle is very close to the ideal tetrahedral value,...
¹H NMR of Conformationally Flexible Molecules: Temporal Resolution
Unsymmetric Bending - Angle of Neutral Axis
When a bending moment is applied at an angle θ concerning the vertical axis of a symmetrical member, it can be resolved into components along the member's principal centroidal axes. The...
Torsion of Noncircular Members
¹H NMR of Conformationally Flexible Molecules: Variable-Temperature NMR
Chair Conformation of Cyclohexane
The hydrogen atoms linked to carbons are arranged in two different axial and equatorial orientations to achieve this staggered...

