Is Alexa Fluor 647 the same as APC?

Alexa Fluor 647 vs APC: A Detailed Comparison

Alexa Fluor 647 and Allophycocyanin (APC) are both fluorescent dyes used extensively in the field of biochemistry and cell biology for labeling proteins, antibodies, and other molecules for fluorescence microscopy, flow cytometry, and other fluorescence-based detection methods. Despite their common use in similar applications, they are distinct in their chemical properties, fluorescence characteristics, and applications.

Chemical Properties

• Alexa Fluor 647: A synthetic dye designed for high photostability and brightness. It is part of the Alexa Fluor family, known for their stability and resistance to photobleaching.
• APC: A natural fluorescent protein derived from algae. It is a phycobiliprotein and has a larger molecular weight compared to synthetic dyes like Alexa Fluor 647.

Fluorescence Characteristics

• Alexa Fluor 647: Excited at 650 nm and emits at 665 nm. Known for its high quantum yield and brightness.
• APC: Excited at approximately 650 nm and emits at about 660 nm. It is also highly fluorescent but has a bulkier structure due to its protein nature.

Applications

• Alexa Fluor 647: Due to its small size and high photostability, it is preferred for applications where long-term imaging or multiple excitations are required.
• APC: Often used in flow cytometry and cell sorting where its larger size and natural origin are not limiting factors. It is commonly conjugated to antibodies for these applications.

In summary, while Alexa Fluor 647 and APC serve similar purposes in the realm of fluorescent labeling, they differ significantly in their chemical nature, fluorescence properties, and optimal applications. Choosing between them depends on the specific requirements of the experiment, including considerations of photostability, brightness, and molecular size.