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Merocyanine 540
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Introduction:
Merocyanine 540 is a fluorescent lipophilic probe which binds preferentially to membranes with
loosely packed lipids and as such stains apoptotic cells more brightly than normal cells. This change
is due to an increase in fluorescence which occurs with the loss of membrane symmetry. Lymphocytes
undergoing apotposis loosen the packing of lipids on their surface. Changes in merocyanine 540
fluorescence have been shown to generally correlate with the translation of membrane phosphatidyl
serine from the inner to the outer leaflet of the plasma membrane (1).
Application:
Merocyanine 540 stains intact cells so that cells programmed to die but still undisrupted can be
sorted from non-apoptotic cells on the basis of their increased merocyanine 540 staining. In general
there is a close correlation between Annexin V and merocyanine 540 in staining pattern, however
small differences in percentage of stained cells may be seen in some cell types (2). The advantage
of using merocyanine 540 is that it is a simple one step staining procedure which can be combined
with an antibody for a cell membrane antigen allowing phentoypic analysis of the apoptotic
cells.
Instructions for using Merocyanine 540:
- Add 10 ml merocyanine 540 (IQP-198) to 100 ml cell suspension.
- Incubate for 15 minutes.
- Analyze by flow cytometer.
- Merocyanine 540: excitation 488 nm/emission 560; Annexin V excitation 488 nm/ emission 512)
References:
1 Castedo,M., et al.., 1996 J.Immunol. 157. 512-521
2. Frey, T., 1997. Cytometry, 28. 253-263.
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