Chicken Erythrocyte Nuclei
These nuclei, which have multiple peaks, are excellent for checking instrument linearity.
2.0 mL Catalog No.  1006$91.00

BioSure® Chicken Erythrocyte Nuclei (CENs) are an internal biological reference material that can function as a performance standard when calibrating and troubleshooting flow cytometers. This control can be used as a reference for all types of cells. CENs are isolated from fresh chicken blood and fixed in ethanol-PBS. The procedure yields single nuclei, doublets, triplets and a few larger aggregates. DNA linear scale histograms of propidium iodide (PI) stained nuclei exhibit multiple peaks; single nuclei constitute peak one (nearest the ordinate) while the next three peaks to the right have mean channel values which are approximately 2, 3, and 4 times greater than the single nuclei peak. A properly aligned flow cytometer will also have a CV for the single nuclei peak of less than or equal to 3%. The published genome size is 2.5 picograms1.


BioSure® CENs are supplied as an unstained suspension in 2.0 milliliter volumes. The nuclei count per milliliter is at least 2.0 X 107.


CENs are stable at 2° - 8° C until the expiration date denoted on each vial label.


To 48 milliliters of calcium and magnesium free Dulbecco's PBS, add 2.5 mg of propidium iodide (PI) and 0.3 mL of Nonidet P40 (NP40). Mix the solution and Q.S. to 50 mL. Staining solution is stable at 2° - 8° C for at least 30 days when stored protected from light in an amber bottle.


The recommended working solution is a 1:10 dilution of the stock CENs in the PI stain prepared previously. This provides an adequate density of nuclei and sufficient working solution for several hours.

Typical CEN graph

1. Gently mix the CEN stock for 5 - 10 seconds to suspend the nuclei, and add one or two drops to a test tube (13 X 75 mm).

2. Add 1.0 mL of PI stain, mix for 5 - 10 seconds, and incubate at room temperature (22°- 25° C) for 10 minutes protected from light.

3. Mix sample 5 - 10 seconds and evaluate. Samples are typically stable at 2° - 8° C for 4 hours when protected from light.

NOTE: The flow cell of some cytometers is susceptible to clogging. Filtering the stained preparation through a 30 - 50 mesh nylon screen will eliminate large nuclear aggregates.


Although the Negative Control has been thoroughly washed to remove residual fixative, the chemical is hazardous, and it is recommended that gloves and eye protection be worn when handling this product.

1 Gregory, T.R.; Animal Genome Size Database: 2001-2005, available at

  • Initial Standardization
  • Daily Monitoring
  • Sensitivity Assessment
  • Alignment & Linearity
  • Biological Safety Data
  • Material Safety Data Sheet

Check your Cytometer Performance with BioSure® CENs

Here's everything you need to know about using BioSure® Chicken Erythrocyte Nuclei (CENs) for cytometer alignment and linearity checks. It's so easy and effective, you'll want to make it a routine process in your lab! It's so economical, you can do this check daily, or whenever your instrument appears not to be performing. Get ready for optimized performance.

Alignment and Linearity Procedure

All you do is prepare the PI solution, prepare a working solution with BioSure® CENs, incubate, analyze, and evaluate.

Prepare the BioSure® PI Solution

  1. 1. Remove 4.0 mL of PI Staining Buffer from Bottle B and add it to the PI Stain in Bottle A.
    CAUTION: Wear gloves and protective eye wear when handling the PI Stain and solution. Always handle and dispose of bottles and contents in accordance with good laboratory practices.
  2. 2. Replace the cap on Bottle A and gently invert the bottle several times.
  3. 3. Pour the contents of Bottle A into Bottle B and mix.
  4. 4. Rinse Bottle A with 4.0 mL of the mixture in Bottle B to remove any remaining dye and add the mixture back into Bottle B.
  5. 5. Place the enclosed PI Staining Solution label over the label on Bottle B and store at 2° - 8° C. The staining solution is ready for use.

Prepare the Working Solution

The recommended working solution is a 1:10 dilution of BioSure® CENs to PI Staining solution. This dilution provides an adequate density of nuclei for analysis, and supplies sufficient working solution for several hours.

  1. 1. Gently mix BioSure® CENs for 5 - 10 seconds to suspend the nuclei.
  2. 2. Add one or two drops of CENs to a 13 x 75-mm test tube.
  3. 3. Add 1.0 mL of PI stain to the test tube, mix for 5 - 10 seconds, and incubate at room temperature (22° - 25° C) for 10 minutes. Protect from light.
  4. 4. Mix the sample for 5 - 10 seconds before analyzing.

Evaluate the Linearity and Alignment

Look at the single-nuclei peak near the ordinate, and the other peaks with mean channel values about two, three, and four times greater. The flow cytometer is properly aligned when CV's for the single, double, and triple peaks are less than or equal to 3%.

Procedural Notes

  1. 1. The mixed BioSure® PI staining solution is stable for at least 90 days when refrigerated at 2° - 8° C in the amber bottle.
  2. 2. BioSure® CENs are stable when refrigerated at 2° - 8° C, until the expiration date on each vial label.
  3. 3. Mixed samples (PI solution and CENs) remain stable for four hours when refrigerated at 2° - 8° C and protected from light.
  4. 4. The flow cells of some cytometers are susceptible to clogging. If clogging occurs, filter the stained preparation through a 30 to 50 micron mesh nylon screen to eliminate large nuclear aggregates.

Biological Safety Data

This product is manufactured by BioSure®, Inc. as a biological research product. To the best of our knowledge, this product does not contain concentrations of carcinogenic, teratogenic or chemical agents that exceed 0.1% or greater in accordance with OSHA’s Hazardous Communication Standard 29CFR1910.1200 (d) (5) (i-iv). This product is exempt from the Material Safety Data Sheet requirements. Biological research controls should be handled using proper laboratory safety procedures, such as gloves, eye protection etc. Disposal can be by normal sewage. However, autoclaving or incineration is recommended should this product be mixed with hazardous or infectious materials such as human or animal serum, plasma, whole blood or tissue. If you have further questions, please call us at 800-345-2267 or email us at