Alexa dyes, a series of new fluorescent dyes that yield exceptionally bright, photostable conjugates

Alexa 350, Alexa 430, Alexa 488, Alexa 532, Alexa 546, Alexa 568, and Alexa 594 dyes are a new series of fluorescent dyes with emission/excitation spe ctra similar to those of AMCA, Lucifer Yellow, fluorescein, rhodamine 6G, t etramethylrhodamine or Cy3, lissamine rhodamine B, and Texas Red, respectiv ely (the numbers in the Alexa names indicate the approximate excitation wav elength maximum in nm). All Alexa dyes and their conjugates are more fluore scent and more photostable than their commonly used spectral analogues list ed above. In addition, Alexa dyes are insensitive to pH in the 4-10 range. We evaluated Alexa dyes compared with conventional dyes in applications usi ng various conjugates, including those of goat anti-mouse IgG (GAM), strept avidin, wheat germ agglutinin (WGA), and concanavalin A (ConA). Conjugates of Alexa 546 are at least twofold more fluorescent than Cy3 conjugates. Pro teins labeled with the Alexa 568 or Alexa 594 dyes are several-fold brighte r than the same proteins labeled with lissamine rhodamine B or Texas Red dy es, respectively. Alexa dye derivatives of phalloidin stain F-actin with hi gh specificity. Hydrazide forms of the Alexa dyes are very bright, formalde hyde-fixable polar tracers. Conjugates of the Alexa 430 (ex 430 nm/em 520 n m) and Alexa 532 (ex 530 nm/em 548 nm) fluorochromes are spectrally unique fluorescent probes, with relatively high quantum yields in their excitation and emission wavelength ranges.