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.  (Unit Size)
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
Alexa Fluor® 488  Avidin

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

Alexa Fluor®–Phycobiliprotein Streptavidin Conjugates

Life Technologies™ offers 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.  (Unit Size)
Alexa Fluor® 610–R-PE  Streptavidin
496, 546, 565 †
Alexa Fluor® 647–R-PE  Streptavidin
496, 546, 565 †
Alexa Fluor® 680–R-PE  Streptavidin
496, 546, 565 † 
Alexa Fluor® 750–R-PE  Streptavidin
496, 546, 565 † 
APC and Tandem-APC Conjugates
Streptavidin Conjugates   Ex (nm)* Em (nm)*  Cat . No.  (Unit Size)
Allophycocyanin (APC)  Streptavidin
S868, S32362
Alexa Fluor® 680–APC  Streptavidin
Alexa Fluor® 700–APC  Streptavidin
Alexa Fluor® 750–APC  Streptavidin
*Approximate fluorescence excitation (Ex) an d emission (Em) maxima for conjugates, in nm

All-in-One Kits for Fluorescence Imaging

The Image-iT® FX Kits provide all of the dyes and reagents you need for optimal immunofluorescence imaging of fixed cells and tissue sections using Alexa Fluor® fluorescent streptavidin conjugates. Each kit includes:
A pack of two CultureWell® (Grace Bio-Labs) chambered cover glasses is also included for convenient processing. Each Image-iT® FX Kit provides sufficient materials to perform 50–100 assays.
Alexa Fluor® Labeling Kits