Distinguishing Molecular Mechanical Action from Photothermal and Photodynamic Behavior

Abstract

Molecular motors (MM) are molecular machines, or nanomachines, that rotate unidirectionally upon photostimulation and perform mechanical work on their environment. In the last several years, it has been shown that the photomechanical action of MM can be used to permeabilize lipid bilayers, thereby killing cancer cells and pathogenic microorganisms and controlling cell signaling. The work contributes to a growing acknowledgement that the molecular actuation characteristic of these systems is useful for various applications in biology. However, the mechanical effects of molecular motion on biological materials are difficult to disentangle from photodynamic and photothermal action, which are also present when a light‐absorbing fluorophore is irradiated with light. Here, an overview of the key methods used by various research groups to distinguish the effects of photomechanical, photodynamic, and photothermal action is provided. It is anticipated that this discussion will be helpful to the community seeking to use MM to develop new and distinctive medical technologies that result from mechanical disruption of biological materials.

Molecular Shuttles with a Photoresponsive Macrocycle: Investigating Interactions and Operation within Lipid Membranes

“…Such fine-tuned control could be exploited to modulate lipid-lipid and lipid-protein interactions, critical for different cellular processes. [13][14][15][16][17] Smith and coworkers provided evidence that the wobbling motion of certain rotaxanes within lipid bilayers is sufficient to induce local defects in the headgroup region, promoting the translocation of phospholipids across the lipid membrane via a "slip-pop" mechanism. 18 However, this rotaxane lacked shuttling motion as the axle featured only a single recognition site for the macrocycle.…”