Practice question

Immunofluorescence demands bright, photostable red emitters distinguishable from green fluorescein and blue nuclear stains. Alexa 568 absorbs near 578 nanometers and emits near 603 nanometers in orange-red region, providing excellent spectral separation from Alexa 488 and DAPI. When conjugated to secondary antibodies, it specifically marks target antigens like tubulin, actin or membrane receptors with low background and persistent signal during z-stack acquisition. FITC and GFP emit green, while DAPI emits blue, making them unsuitable for red channel labeling in three-color panels requiring distinct detection windows.