From: Abe Schwartz (73437.2722@CompuServe.COM)
Date: Mon Nov 25 1996 - 11:56:45 EST
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 determined. 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 used. I hope this information clarifies what MESF units are and how they are used. Best regards, Abe Schwartz, PhD President, FCSC
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