Mouse UltraAvidin FITC Staining Kit

The immunofluorescent staining method is preferred to distinguish fine subcellular structures in fixed tissue sections. The avidin-biotin system for immunostaining has increased the sensitivity for detecting very small amounts of antigen and definitive negative controls can be used as compared to the direct method of labelling.1-3 In this method, the secondary antibody directed against the immunoglobulin of the species in which the first antibody is raised, is biotin labeled. This is allowed to react with the primary antibody, followed by the addition of the fluorescein-conjugated UltraAvidin forming a complex whereby many fluorescein molecules are indirectly bound to each secondary antibody.4,5 The avidin has an extraordinary affinity for the small molecule biotin forming a noncovalent bond with a dissociation constant of 10-15M making this system highly stable.5,6 The bound conjugate is then visualized using a fluorescence microscope. The fluorochrome is excited by use of the appropriate light source. The light emitted is filtered by appropriate filters to remove stray light and allow the observer's eye to visualize fluorescent light from the fluorochrome.1 Fluorescein has a maximum absorbance at 492nm (blue) and an emission maximum at 518nm (green). It is covalently attached to UltraAvidin and purified to assure an optimal fluorochrome/protein molar ratio.

Leinco's UltraAvidin is a unique form of avidin, modified to prevent non-specific binding on cell surfaces either due to lectin-like receptor adherence or electrostatic interactions. The secondary Goat anti-mouse IgG antibody is a F(ab/)2 fragment, eliminating non-specific Fc receptor binding and is especially suitable for immunohistochemical studies. It is affinity isolated using Mouse IgG and is adsorbed against human serum proteins to reduce cross-reactivity with human tissue sections. The antibody is then conjugated to biotin at a molar ratio to optimize performance. The kit has been developed for enhanced sensitivity whereby low amounts of antigen may be detected or where lower concentrations of primary antibody may be used.

1. UltraBlock^TM Blocking Buffer - 4 ml
2. Reagent A: Goat Anti-Mouse IgG - Biotin - 1 ml
3. Reagent B: UltraAvidin Fluorescein - 1 ml
4. Mixing Bottles with drop dispenser tips: Mixing bottles are used to prepare the working solutions for the staining kit and to dispense the required amount on each tissue section. (Note: If held vertically upside down the volume of each drop is 45-50 ul. Holding the bottle at an angle would increase drop volume.) Note: Keep bottles closed to prevent microbial or dust contamination. Do not reuse working solutions.

Working Solutions
1. Blocking Buffer: Add 1.0 ml of Blocking Buffer from the Mouse UltraAvidin Fluorescein Staining Kit to 9 ml PBS in the Mixing Bottle 1. Snap on drop dispenser tip.
2. Primary Antibody: Adjust to required concentration with PBS.
3. Biotinylated secondary antibody: Add 1 drop of Reagent A from the Mouse UltraAvidin Fluorescein Staining Kit to 10ml PBS in Mixing Bottle 2.
4. UltraAvidin-Fluorescein: Add 50ul from the Reagent B of the Mouse UltraAvidin Fluorescein Staining Kit to 10ml PBS in Mixing Bottle 3.

Suggested Method
All the steps are carried out at room temperature in moist chambers.
1. For cryostat sections fix in acetone for 10 mins and air dry. Go directly to Step 5.
2. For paraffin sections fix at 35oC for 2-3 minutes.
3. Deparaffinize in xylene for 20 mins.
4. Wash in decreasing grades of ethanol, 10mins in each.
5. Wash under running tap water for 10 mins.
6. Wash in PBS for 10 mins.
7. Wipe slide and add the blocking serum dropwise onto the slide, covering the section. Incubate for 20 mins.
8. Drain out blocking buffer and add primary antibody onto the section, covering it. Incubate for 1 hour.
9. Drain out antibody and wash in PBS for 10 mins.
10. Wipe slides and add the biotinylated secondary antibody onto the section, covering it. Incubate for 30 mins.
11. Drain out antibody and wash in PBS for 10 mins.
12. Wipe the slides and add the UltraAvidin-Fluorescein onto the section, covering it. Incubate for 30 mins.
13. Drain out solution and wash in PBS for 10 mins.
14. Counterstain and mount in glycerol.

(Note: Fluorochrome staining is not stable and cannot be preserved. For best results, it should be observed and photographed, if needed, immediately after processing the section.)

These instructions are for the use of Leinco's Mouse UltraAvidin Fluorescein Staining Kit for immunohistology. The mouse primary antiserum/ antibody is supplied by the user. Reagents supplied are sufficient for at least 1000 tissue sections. When not in use the reagents should be stored at 0-5^C.

1. Peter, J.H. and Baumgarten, H (Eds.) (1992) Monoclonal Antibodies Springer-Verlag, New York, Berlin, Heidelberg