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#fluorescence detection

2 public questions tagged with this topic.

PCR Modifications

What is the primary function of SYBR Green in qPCR?

SYBR Green I is a sensitive double-stranded DNA intercalating dye widely used in real-time PCR. In free solution its fluorescence is minimal, but upon binding to minor groove and intercalation between base pairs of duplex DNA, conformational restriction greatly enhances quantum yield, producing strong green emission under excitation. Signal intensity increases proportionally with amplicon accumulation, allowing quantification without sequence-specific probes. It does not block nonspecific amplification, cleave DNA or quench fluorescence; rather, it serves as reporter of total double-stranded product. Specificity must be confirmed by melt curve analysis since any duplex, including dimers, will fluoresce.

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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Protein-Protein Interaction

BiFC (Bimolecular Fluorescence Complementation) detects:

Bimolecular Fluorescence Complementation is a genetic technique to visualize protein-protein association in living cells. Candidate proteins are fused to non-fluorescent N- and C-terminal fragments of a fluorescent protein such as YFP or Venus. Individually fragments are non-fluorescent. When fused proteins interact, fragments are brought into proximity to refold into functional fluorophore, emitting fluorescence detectable by microscopy or flow cytometry. Irreversible complementation reports localization of interaction. It does not measure RNA cleavage, phosphorylation per se, or mismatch repair but specifically protein-protein interaction.

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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