Probing the orientation and membrane permeation of rhodamine voltage reporters through molecular simulations and free energy calculations.

The transmembrane potential of plasma membranes and membrane-bound organelles plays a fundamental role in cellular functions such as signal transduction, ATP synthesis, and homeostasis. Rhodamine voltage reporters (RhoVRs), which operate based on the photoinduced electron transfer (PeT) mechanism, are non-invasive, small-molecule voltage sensors that can detect rapid voltage changes, with some of them specifically targeting the inner mitochondrial membrane. In this work, we conducted extensive molecular dynamics simulations and free-energy calculations to investigate the physicochemical properties governing the orientation as well as membrane permeation barriers of three RhoVRs.

Orientation and Membrane Partition Free Energy of PeT-Based Voltage-Sensitive Dyes from Molecular Simulations.

Voltage measurement via small-molecule fluorescent indicators is a valuable approach in deciphering complex dynamics in electrically excitable cells. However, our understanding of various physicochemical properties governing the performance of fluorescent voltage sensors based on the photoinduced electron transfer (PeT) mechanism remains incomplete. Here, through extensive molecular dynamics and free energy calculations, we systematically examine the orientation and membrane partition of three PeT-based voltage-sensing VoltageFluor (VF) dyes in different lipid environment.