EverGreen: A Calcium Sensing Fluorescent Protein with Ultra-Slow Response Properties

EverGreen, a green fluorescent protein calcium biosensor, extends a decay component to 6.1 min, enabling fluorescence detection minutes after calcium fluctuations dissipate.

• Why it matters: Fast calcium indicators can be hard to use when read-out timing is constrained, such as with plate readers or cell sorters. Slower decay could better match experimental workflows that cannot tightly couple activation and measurement.
• What they did: The authors engineered EverGreen by molecular engineering to lengthen a slow component of its decay time constant. They then assessed how long fluorescence remains detectable after calcium changes.
• The result: EverGreen’s fluorescence can be detected for minutes after the underlying calcium fluctuation has already dissipated. This supports synthetic biology directed evolution projects under instrumentation and methodology limits.

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