Visualization of electrical activity in living cells represents an important challenge in context of basic neurophysiological studies. Here we report a new voltage sensitive fluorescent indicator which response could be detected by fluorescence monitoring in a single red channel. To the best of our knowledge, this is the first fluorescent protein-based voltage sensor which uses insertion-into-circular permutant topology to provide an efficient interaction between sensitive and reporter domains. Its fluorescent core originates from red fluorescent protein (FP) FusionRed, which has optimal spectral characteristics to be used in whole body imaging techniques. Indicators using the same domain topology could become a new perspective for the FP-based voltage sensors that are traditionally based on Förster resonance energy transfer (FRET).

Center for Functional Connectomics Korea Institute of Science and Technology Seoul Korea

Central European Institute of Technology Masaryk University Brno Czech Republic

Institute of Higher Nervous Activity and Neurophysiology Moscow Russian Federation

Nizhny Novgorod State Medical Academy Nizhny Novgorod Russia

Pirogov Russian National Research Medical University Moscow Russia

Shemyakin Ovchinnikov Institute of Bioorganic Chemistry Moscow Russian Federation

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