We offer a broad range of Alexa Fluor fluorescent streptavidin conjugates (Table 1 and Table 3) and avidin conjugates (Table 2). These dyes represent a major breakthrough in the development of fluorescent labeling reagents and, without exception, produce the best and brightest conjugates we have ever tested. Benefits of the Alexa Fluor dyes and their conjugates include exceptionally bright conjugatesexcellent photostability, and a broad range of emission colors. These characteristics make Alexa Fluor dyes the best choice for most imaging applications.

Table 1. Alexa Fluor Fluorescent Streptavidin Conjugates

Streptavidin Conjugates Ex (nm)* Em (nm)* Cat . No.
Alexa Fluor 350 Streptavidin 346 442 S11249 (1 mg)
Alexa Fluor 405 Streptavidin 402 421 S32351 (1 mg)
Alexa Fluor 430 Streptavidin 434 539 S11237 (1 mg)
Alexa Fluor 488 Streptavidin 495 519 S11223 (1 mg)
S32354 (0.5 mL)
Alexa Fluor 500 Streptavidin 503 525 S32352 (1 mg)
Alexa Fluor 514 Streptavidin 518 540 S32353 (1 mg)
Alexa Fluor 532 Streptavidin 530 554 S11224 (1 mg)
Alexa Fluor 555 Streptavidin 555 565 S21381 (1 mg)
S32355 (0.5 mL)
Alexa Fluor 546 Streptavidin 556 573 S11225 (1 mg)
Alexa Fluor 568 Streptavidin 578 603 S11226 (1 mg)
Alexa Fluor 594 Streptavidin 590 617 S11227 (1 mg)
S32356 (0.5 mL)
Alexa Fluor 610 Streptavidin 612 628 S32359 (1 mg)
Alexa Fluor 633 Streptavidin 632 647 S21375 (1 mg)
Alexa Fluor 635 Streptavidin 633 647 S32364 (1 mg)
Alexa Fluor 647 Streptavidin 650 668 S21374 (1 mg)
S32357 (0.5 mL)
Alexa Fluor 660 Streptavidin 663 690 S21377 (1 mg)
Alexa Fluor 680 Streptavidin 679 702 S21378 (1 mg)
S32358 (0.5 mL)
Alexa Fluor 700 Streptavidin 702 723 S21383 (1 mg)
Alexa Fluor 750 Streptavidin 749 775 S21384 (1 mg)

*Approximate fluorescence excitation (Ex) an d emission (Em) maxima for conjugates, in nm.

Alexa Fluor Streptavidin Fluorescent Conjugates in Action


Multicolor fluorescence microscopy analysis of muntjac fibroblasts. The actin cytoskeleton was labeled with biotin phalloidin and visualized using Alexa Fluor 350 streptavidin. Mitochondria were stained with MitoTracker Red CMXRos; the nucleus was labeled with an anti-phosphohistone primary antibody and visualized using Alexa Fluor 500 goat anti–mouse IgG.

The cytoskeleton of a fixed and permeabilized bovine pulmonary artery endothelial cell.Tubulin was detected using mouse monoclonal anti–α-tubulin antibody and visualized with Alexa Fluor 647 goat anti–mouse IgG antibody (pseudocolored magenta). Endogenous biotin in mitochondria was labeled with green-fluorescent Alexa Fluor 488 streptavidin; DNA was stained with blue-fluorescent DAPI.


Table 2. Alexa Fluor® NeutrAvidin and Avidin Conjugates

Fluorescent  Conjugate  Ex (nm)* Em (nm)*  Cat . No.
Alexa Fluor 350  Neutravidin 346 442 A11236
Alexa Fluor 488  Avidin 495 519 A21370

*Approximate fluorescence excitation (Ex) an d emission (Em) maxima for conjugates, in nm.<

Alexa Fluor–Phycobiliprotein Streptavidin Conjugates

We offer fluorescent streptavidin conjugates of with tandem dyes R-PE (R-Phycoerythrin) and APC (Allophycocyanin) labeled with long-wavelength Alexa Fluor dyes. Our tandem conjugates (Table 3) comprise a donor phycobiliprotein—R-PE or APC—conjugated to longer wavelength–emitting fluorescence acceptors. By the process of fluorescence resonance energy transfer (FRET), an energy transfer cascade is established wherein most of the light absorbed by the donor R-PE or APC results in fluorescence of the acceptor dye. This process can be quite efficient, resulting in almost total transfer of energy to the acceptor dye.

Table 3. Tandem Alexa Fluor–Phycobiliprotein Streptavidin Conjugates

R-PE, B-PE, and Tandem–R-PE Conjugates
Streptavidin Conjugates   Ex (nm)* Em (nm)*  Cat . No. 
Alexa Fluor 610–R-PE  Streptavidin 496, 546, 565 † 630 S20982
Alexa Fluor 647–R-PE  Streptavidin 496, 546, 565 † 668 S20992
Alexa Fluor 680–R-PE  Streptavidin 496, 546, 565 †  702 S20985
Alexa Fluor 750–R-PE  Streptavidin 496, 546, 565 †  771 S32363
APC and Tandem-APC Conjugates
Streptavidin Conjugates  Ex (nm)* Em (nm)* Cat . No.
Allophycocyanin (APC) Streptavidin 650 660 S868, S32362
Alexa Fluor 680–APC  Streptavidin 650 702 S21002
Alexa Fluor 700–APC  Streptavidin 650 723 S21005
Alexa Fluor 750–APC  Streptavidin 650 775 S21008

*Approximate fluorescence excitation (Ex) an d emission (Em) maxima for conjugates, in nm