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#sensitivity

3 public questions tagged with this topic.

Electrophoresis

Which dye is more sensitive than Coomassie for protein detection?

Sensitivity differences among protein dyes determine detection limits in gels. Coomassie Brilliant Blue R-250 detects roughly 50 to 100 nanograms per band by binding electrostatically to basic and aromatic residues, suitable for routine quantification. Silver staining involves impregnation of gel with silver ions that bind to carboxyl, sulfhydryl and amino side chains, followed by reduction to metallic silver by formaldehyde, achieving 50 to 100-fold greater sensitivity down to 1 to 5 nanograms. Bromophenol blue merely tracks migration front, while ethidium bromide and SYBR Green intercalate nucleic acids, not proteins, limiting their utility.

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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Fluorescence and CD Spectroscopy

Which technique is more sensitive than pH glass electrode?

Fluorescence measurement counts emitted photons against essentially dark background, permitting detection down to picomolar concentrations using photomultipliers and photon counting. Glass pH electrode measures electrochemical potential with inherent drift and limited low-concentration response. Absorption spectrophotometry must discriminate small absorbance difference between intense incident and transmitted beams, restricting sensitivity to micromolar levels. Circular dichroism also detects small differential absorbance. Because quantum yield amplifies signal and background remains low, fluorescent probes track minute changes in ions, pH or metabolites with far superior sensitivity.

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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Flow cytometry, FACS, ELISA

Which enhances ELISA sensitivity without compromising specificity?

Sensitivity in ELISA often enhanced via avidin biotin system without losing specificity. Primary antibody binds antigen, biotinylated secondary antibody binds primary, then streptavidin conjugated enzyme with four biotin binding sites attaches. Each secondary can carry multiple biotins, recruiting many enzyme molecules, amplifying signal dramatically. HRP and ALP alone give single enzyme per antibody. Direct detection lacks amplification steps. Biotinylation preserves antibody specificity because antigen recognition remains unchanged, while enzyme loading increases. This approach lowers detection limit for low abundance proteins and improves signal to noise ratio.

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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