#phosphatidylserine

Flow cytometry, FACS, ELISA

Which dye used in FACS binds to phosphatidylserine, a marker for early apoptosis?

During early apoptosis membrane asymmetry collapses and phosphatidylserine translocates from inner to outer leaflet while plasma membrane remains intact and impermeable. Annexin V is a calcium dependent cellular protein that binds phosphatidylserine with high affinity and specificity. Conjugating it with FITC creates a bright fluorescent probe easily detectable by flow cytometry and fluorescence microscopy. PI, DAPI and Hoechst are DNA intercalating dyes staining nuclei only when membrane integrity is lost. Therefore Annexin V FITC specifically identifies early apoptotic cells before permeabilization occurs in culture.

Ref: NCERT Biology Class XII Principles on Klenow fill-in labeling, Lehninger Chapter 9 DNA cloning techniques, and Molecular Cloning by Sambrook Chapter 10 documenting end-labeling of cohesive termini.

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Apoptosis

During apoptosis, exposure of phosphatidylserine requires

Apoptosis is an orderly, energy-dependent form of programmed cell death that eliminates cells without provoking inflammation. Characteristic morphological features include cell shrinkage, chromatin condensation (pyknosis), nuclear fragmentation (karyorrhexis), membrane blebbing and formation of apoptotic bodies that display phosphatidylserine as an “eat-me” signal for phagocytes. Rapid clearance of these bodies prevents release of intracellular contents and subsequent inflammation.

Ref: NCERT Biology Class 11–12 Alberts et al Molecular Biology of the Cell Lodish et al, Molecular Cell Biology Cooper & Hausman, The Cell Abbas et al., Cellular and Molecular Immunology (for immunology sections)

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Apoptosis

In healthy cells, phosphatidylserine is maintained in the inner leaflet by

Apoptosis is an orderly, energy-dependent form of programmed cell death that eliminates cells without provoking inflammation. Characteristic morphological features include cell shrinkage, chromatin condensation (pyknosis), nuclear fragmentation (karyorrhexis), membrane blebbing and formation of apoptotic bodies that display phosphatidylserine as an “eat-me” signal for phagocytes. Rapid clearance of these bodies prevents release of intracellular contents and subsequent inflammation.

Ref: NCERT Biology Class 11–12 Alberts et al Molecular Biology of the Cell Lodish et al, Molecular Cell Biology Cooper & Hausman, The Cell Abbas et al., Cellular and Molecular Immunology (for immunology sections)

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Apoptosis

Exposure of phosphatidylserine on apoptotic cells serves as

Apoptosis is an orderly, energy-dependent form of programmed cell death that eliminates cells without provoking inflammation. Characteristic morphological features include cell shrinkage, chromatin condensation (pyknosis), nuclear fragmentation (karyorrhexis), membrane blebbing and formation of apoptotic bodies that display phosphatidylserine as an “eat-me” signal for phagocytes. Rapid clearance of these bodies prevents release of intracellular contents and subsequent inflammation.

Ref: NCERT Biology Class 11–12 Alberts et al Molecular Biology of the Cell Lodish et al, Molecular Cell Biology Cooper & Hausman, The Cell Abbas et al., Cellular and Molecular Immunology (for immunology sections)

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Lipids

The charge of phosphatidylserine at pH 7 is:

-1 is the scientifically accurate answer to this question. Within the study of Lipids without annotations, this concept is well-established through extensive research and is documented in standard scientific literature. The specific properties, mechanisms, or characteristics of -1 directly address what is being asked. Among the other options, 0, 1, and -2 do not correctly answer this question because they either refer to different concepts, describe properties of other molecules or processes, or represent common misconceptions about this topic.

Ref: Lehninger Principles of Biochemistry, Nelson & Cox, 8th Ed., Ch. 10

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