Observation of contraction and expansion in a bis(peptide)-based mechanical molecular actuator.

A novel, bis(peptide) based molecular actuator (1) has been synthesized. It is demonstrated to undergo contraction and expansion controlled by the addition and removal of Cu2+; this is demonstrated by the direct observation of a change in hydrodynamic properties by using sedimentation analysis and size exclusion chromatography. The molecule undergoes a large change in sedimentation coefficient, axial ratio, and size exclusion chromatography elution time when it binds copper. The demonstration of a controlled change in the mechanical properties of 1 make it a good starting point for the development of molecular devices that will harness changes in molecular shape and size to create molecular devices such as sensors or valves.