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RhodaMal Dyes: Novel Red Emissive Fluorophores as Probes for High Contrast Live-Cell Imaging
A Mavroskoufis1, P Aßmann1, L M Filla1
1Institute of Chemistry and Biochemistry, Freie Universität Berlin, Berlin, Germany.
Chemistry (Weinheim an Der Bergstrasse, Germany)
|July 18, 2026
Summary
Researchers developed new red fluorescent dyes, RhodaMal 620 and RhodaMal 638, for advanced microscopy. These dyes show enhanced fluorescence in viscous environments and enable super-resolution imaging of mitochondria.
Area of Science:
- Organic Chemistry
- Biophysical Chemistry
- Cell Biology
Background:
- Red and near-infrared emitting dyes are crucial for fluorescence microscopy applications.
- Traditional rhodol frameworks are widely used but can be improved for specific imaging needs.
Purpose of the Study:
- To synthesize and characterize novel red emissive dyes, RhodaMal 620 and RhodaMal 638.
- To investigate the photophysical properties and potential applications of these new dyes in fluorescence imaging.
Main Methods:
- Incorporation of malononitrile moiety into the rhodol framework to create new dyes.
- Spectroscopic analysis in aqueous solutions and varying viscosity media.
- Mitochondrial targeting via conjugation with triphenylphosphonium cation (TPP+).
- Super-resolution imaging using Stimulated Emission Depletion (STED) microscopy.
Main Results:
- RhodaMal 620 and RhodaMal 638 exhibit absorption/emission maxima at 620/638 nm and 664/708 nm.
- A significant 20-fold increase in fluorescence signal was observed in high-viscosity media.
- TPP+-conjugated dyes demonstrated efficient mitochondrial localization.
- Live cell STED microscopy achieved super-resolution imaging with a 77 nm resolution.
Conclusions:
- The new RhodaMal dyes offer enhanced fluorescence properties, particularly in crowded cellular environments.
- These dyes are suitable for mitochondrial targeting and advanced super-resolution microscopy.
- The developed dyes represent a valuable tool for high-resolution live cell imaging.
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