Is Alexa Fluor 488 the same as Fitc?

Differences Between Alexa Fluor 488 and FITC

Alexa Fluor 488 and Fluorescein Isothiocyanate (FITC) are both fluorescent dyes used widely in various biological applications such as flow cytometry, fluorescence microscopy, and immunoassays. Despite their common usage in labeling proteins, antibodies, and other molecules for fluorescent detection, they are not the same compound and have distinct characteristics.

Chemical Structure

Alexa Fluor 488: It is a sulfonated rhodamine derivative with enhanced photostability.

FITC: It is a derivative of fluorescein with an isothiocyanate reactive group that allows it to covalently attach to amines at high pH levels.

Spectral Properties

Alexa Fluor 488: It has an excitation peak at 495 nm and an emission peak at 519 nm.

FITC: It has an excitation peak at 494 nm and an emission peak at 518 nm. While similar, the narrower emission spectrum of Alexa Fluor 488 generally provides a better signal-to-noise ratio.

Photostability

Alexa Fluor 488: Known for its improved photostability, allowing it to retain fluorescence longer under the microscope or in a flow cytometer.

FITC: Less photostable than Alexa Fluor 488, which leads to quicker photobleaching.

Applications

• Alexa Fluor 488: Commonly used where higher photostability is required or when multiple fluorescent dyes are used, for it has less bleed-through.
• FITC: Often employed for routine detection when photostability is not the primary concern.

In summary, Alexa Fluor 488 and FITC are both green-fluorescent dyes with similar excitation and emission wavelengths but they differ in their chemical structures, photostability, and some aspects of their application. Alexa Fluor 488 is generally preferred for more demanding applications due to its greater photostability and specific spectral properties.