cholera toxin subunit B （recombinant）

Fluorescence Spectra

Alexa Fluor® 594 goat anti mouse IgG antibody/pH 7.2

Absorption and fluorescence emission spectra of Alexa Fluor® 594 goat anti–mouse IgG antibody in pH 7.2 buffer.

 

Description
The Alexa Fluor 594 cholera toxin subunit B conjugate is labeled with our bright, photostable, red-fluorescent Alexa Fluor 594 dye （which is spectrally similar to Texas Red dye）. The conjugate is derived from nontoxic recombinant B subunit, so it is compley free of the toxic A subunit. Alexa Fluor 594 cholera toxin subunit B conjugate is also available in a unit size of 500 µg （C-22842）.

Revised:  02?September?2003
Product Information
Cholera Toxin Subunit B （CT-B） Conjugates
Storage upon receipt:
? ≤ ?20°C
? Desiccate
? Protect from light
Abs/Em:  See Table 1
Introduction
Table 1.  Conjugates of cholera toxin subunit B.
Unit Size  Label  Abs/Em *
100 µg 500 µg
Alexa Fluor 488  495/519  C-34775  C-22841
Alexa Fluor 555  555/565  C-34776  C-22843
Alexa Fluor 594  590/617  C-34777  C-22842
Alexa Fluor 647  650/668  C-34778  
Biotin NA C-34779 
Horseradish
peroxidase （HRP）
NA C-34780 
* Approximate absorption （Abs） and fluorescence emission （Em） maxima, in nm.  NA = Not
applicable. 

Cholera toxin from Vibrio cholerae is comprised of two sub-
units, A and B, arranged in an AB5
 configuration. The A subunit
is an ADP-ribosyltransferase, which disrupts the proper signal-
ing of G proteins and eventually leads to dehydration of the cell.
1
The nontoxic B subunit is important to the protein complex as it
allows the protein to bind to cellular surfaces via the pentasac-
charide chain of ganglioside GM1
.
2
 At neutral pH, the 11.4 kDa
B subunit exists as a 57 kDa pentamer.
3
The B subunit of cholera toxin （CT-B） has proven to be a
powerful tool for retrograde labeling of neurons.
4,5
 This tracer
has been used in a variety of applications, including tracing of ra
forebrain afferents,
6
 projections of the parabrachial region 7
 and
neurons of the urinary bladder wall.
8
 More recently, researchers
have found that CT-B can be used as a marker for lipid rafts,
which are membrane microdomains enriched in cholesterol and
sphingolipids. Lipid rafts segregate specific groups of proteins
and thereby provide a hub for cellular signaling and protein traf-
ficking.
9, 10
Molecular Probes’ CT-B conjugates （Table 1） are made from
recombinant cholera toxin subunit B.  Because the B-subunit
source material is recombinant in origin, it is extremely pure and
compley free of the toxic A subunit.

powder in 0.1 mL or 0.5 mL of buffer, for example, phosphate-
buffered saline （PBS）. With the addition of 2 mM sodium azide,
solutions can be stored at 2–6°C for approximay three months.
For longer storage, divide the solution into aliquots and freeze at
≤–20°C.
The peroxidase conjugates of cholera toxin B are supplied in a
unit size of 100 µg. When stored desiccated at –20°C, the lyo-
philized powder is stable for at least six months. Solutions of
1.0 mg/mL can be prepared by dissolving the powder in 0.1 mL
of PBS, pH 7.2. Store solutions at 2–6°C with the addition of
thimerosal to a final concentration of 0.02%. DO NOT USE
AZIDE for the HRP-conjugates. For prolonged storage after re-
constitution, add glycerol to a final concentration of 50% （v/v）,
aliquot and store at –20°C. When stored properly, solutions are
stable for approximay three months. PROTECT FROM
LIGHT.  AVOID REPEATED FREEZING AND THAWING OF
SOLUTIONS.
For the Alexa Fluor and biotin conjugates, the lot-specific
degree of labeling （typically 5–10 moles of dye per mole of the
B subunit pentamer） is indicated on the product label.

Product List  Current prices may be obtained from our Web site or from our Customer Service Department.
Cat # Product Name Unit Size
C-34775 cholera toxin subunit B （recombinant）, Alexa Fluor? 488 conjugate .......................................................................................... 100 µg
C-22841 cholera toxin subunit B （recombinant）, Alexa Fluor? 488 conjugate .......................................................................................... 500 µg
C-34776 , Alexa Fluor? 555 conjugate .......................................................................................... 100 µg
C-22843 , Alexa Fluor? 555 conjugate .......................................................................................... 500 µg
C-34777 , Alexa Fluor? 594 conjugate .......................................................................................... 100 µg
C-22842 , Alexa Fluor? 594 conjugate .......................................................................................... 500 µg
C-34778 , Alexa Fluor? 647 conjugate .......................................................................................... 100 µg
C-34779 , biotin-XX conjugate ....................................................................................................... 100 µg
C-34780 , horseradish peroxidase conjugate ........................................................ ........................ 100 µg

Materials
The biotin- and dye-labeled cholera toxin B subunits are sup-
plied in unit sizes of 100 µg and 500 µg. When stored desiccated
at ≤–20°C, these products are stable for at least six months.
Solutions of 1.0 mg/mL can be prepared by dissolving the

Due to the diversity of applications for the cholera toxin sub-
unit B, please consult the primary literature for appropriate work-
ng concentrations.

References
1. J Biol Chem 255, 1252 （1980）;  2.  Mol Microbiol 13, 745 （1994）;  3. Biochemistry 35, 16069 （1996）;  4. Brain Res 243 215 （1982）;  5. Brain Res 231, 33
（1982）;  6. Neuroscience 82, 443 （1998）;  7. Brain Res 816, 364 （1999）;  8. Neuroscience 87, 275 （1998）;  9. J Cell Biol 147, 447 （1999）;  10. J Cell Biol 141, 929
（1998）.