MESF Calculations

Abe Schwartz 73437.2722 at CompuServe.COM
Mon Nov 25 11:56:45 EST 1996

Dear Collegues:

MESFs were developed to provide a meaningful "absolute" unit of
fluorescence intensity which was instrument independent.  MESFs for
standard particles are established via spectrofluormetry directly against
solutions of high purity fluorochome which have the same excitation and
emission spectra  and are as responsive to the environment as the labeled
samples, e.g., pH.  Meeting these criteria, automatically provides
correction for differences in extinction coefficients, quenching and
changes in quantum efficiency which would be necessary to consider if
actual numbers of fluorochrome molecules on the standard particles were

The following references may provide useful information:

Schwartz, A.,   Monograph: Fluorescent Microbead Standards, pub FCSC 1988.
Schwartz, A. and Fernandez-Repollet, E., Technical Aspects of Fluorescence
   Quantitative Measurements by Flow Cytometry, Clinical Immunology      
   Newsletter vol 15 (6/7) pp. 73-77  1995.
Schwartz, A. and Fernendez-Repollet, E., Development of Clinical        
   Standards for Flow Cytometry, Annals of NY Acad. of Sci., vol 677 pp.
   28-39, 1993.
Schwartz, A., Fernandez-Repollet, E., Vogt, R. and Gratama, J.W.,        
   Standardizing Flow Cytometry: Construction of a Standardized        
   Fluorescence Calibration Plot Using Matching Spectral Calibrators,    
   Cytometry (Comm in Clinical Cytometry) 26:22-31, 1996.

Note, the determining MESFs of a sample does not accurately indicate the
number of antibodies binding to the sample (Antibody Binding Capacity,
ABC) unless the "effective F/P" ratio or antibody binding standards are

I hope this information clarifies what MESF units are and how they are

Best regards,

Abe Schwartz, PhD
President, FCSC

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