A new bright red fluorescent protein that represented an important advancement was successfully created in 2016 by the research group led by biologist Dorus Gadella from the University of Amsterdam. That protein was given a name: mScarlet. The scientific community immediately recognized their red-hot protein. Nearly every country in the world is now using mScarlet DNA coding for cell biology research after it was requested 3,400 times.

Unfortunately, the mScarlet protein was found to fold more slowly and incompletely in mammalian cells than the commonly used green-fluorescent proteins, resulting in less than ideal brightness in these cells. The scientists continued to work on the protein to speed up and maximize folding.

A research team from the University of Amsterdam, led by Dorus Gadella, has developed a new bright red fluorescent protein: mScarlet3. They published the properties and DNA code of this protein.

They applied two mScarlet variations they had already made: one with fast folding but reduced brightness, and one with slow folding but ultimately brilliant fluorescence. They tried to create a new protein by fusing together the beneficial aspects of the two. They did this by making several precise adjustments to the protein’s structure, creating mScarlet3. The most recent version now combines the highest brightness with fast and thorough folding.

Finally, the biologists sent mScarlet3 to the Institut de Biologie Structurale in Grenoble (CNRS, CEA, Université Grenoble Alpes) for structural testing. The world’s brightest X-ray source, the European Synchrotron ESRF, was used by structural biologist Antoine Royant to map the molecular structure of the protein.

Royan said, “It turned out that mScarlet3 is so bright because of a special hydrophobic (oily) local structure in the protein, which both accelerates and enhances the folding of the protein.”

With this new, much improved version of the red fluorescent protein, the toolbox available to scientists in the lab is now more complete than ever.

gadella said, “Experiences with mScarlet have already been very positive, so we expect mScarlet3 to become even more popular among researchers and quickly become the new standard worldwide. Bright red fluorescent proteins are highly sought after because excitation of these red proteins is less harmful to cells than exciting green proteins.”

“Moreover, red light is scattered less, so that you can also look at molecular processes in deeper cell layers with the microscope. With mScarlet3 we finally have a very robust bright red fluorescent protein that folds quickly and completely without any further drawbacks. We expect a lot from new applications with mScarlet3, including the creation of new red fluorescent biosensors in which mScarlet3 can be used to visualize specific cell functions.”

Magazine reference:

  1. Theodorus WJ Gadella Jr*, Laura van Weeren, Jente Stouthamer, Mark A. Hink, Anouk HG Wolters, Ben NG Giepmans, Sylvain Aumonier, Jérôme Dupuy, Antoine Royant; mScarlet3: a brilliant and rapidly maturing red fluorescent protein; Nature Methods, Doi: 10.1038/s41592-023-01809-y