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 ConjugatesEx (nm)*Em (nm)*Cat . No.
Alexa Fluor 350 Streptavidin346442S11249 (1 mg)
Alexa Fluor 405 Streptavidin402421S32351 (1 mg)
Alexa Fluor 430 Streptavidin434539S11237 (1 mg)
Alexa Fluor 488 Streptavidin495519S11223 (1 mg)
S32354 (0.5 mL)
Alexa Fluor 500 Streptavidin503525S32352 (1 mg)
Alexa Fluor 514 Streptavidin518540S32353 (1 mg)
Alexa Fluor 532 Streptavidin530554S11224 (1 mg)
Alexa Fluor 555 Streptavidin555565S21381 (1 mg)
S32355 (0.5 mL)
Alexa Fluor 546 Streptavidin556573S11225 (1 mg)
Alexa Fluor 568 Streptavidin578603S11226 (1 mg)
Alexa Fluor 594 Streptavidin590617S11227 (1 mg)
S32356 (0.5 mL)
Alexa Fluor 610 Streptavidin612628S32359 (1 mg)
Alexa Fluor 633 Streptavidin632647S21375 (1 mg)
Alexa Fluor 635 Streptavidin633647S32364 (1 mg)
Alexa Fluor 647 Streptavidin650668S21374 (1 mg)
S32357 (0.5 mL)
Alexa Fluor 660 Streptavidin663690S21377 (1 mg)
Alexa Fluor 680 Streptavidin679702S21378 (1 mg)
S32358 (0.5 mL)
Alexa Fluor 700 Streptavidin702723S21383 (1 mg)
Alexa Fluor 750 Streptavidin749775S21384 (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  Neutravidin346442A11236
Alexa Fluor 488  Avidin495519A21370

*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  Streptavidin496, 546, 565 †630S20982
Alexa Fluor 647–R-PE  Streptavidin496, 546, 565 †668S20992
Alexa Fluor 680–R-PE  Streptavidin496, 546, 565 † 702S20985
Alexa Fluor 750–R-PE  Streptavidin496, 546, 565 † 771S32363
APC and Tandem-APC Conjugates
Streptavidin Conjugates Ex (nm)*Em (nm)*Cat . No.
Allophycocyanin (APC) Streptavidin650660S868, S32362
Alexa Fluor 680–APC  Streptavidin650702S21002
Alexa Fluor 700–APC  Streptavidin650723S21005
Alexa Fluor 750–APC  Streptavidin650775S21008

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