What does ninhydrin detect on electrophoresis paper?
Ninhydrin, or 2,2-dihydroxy-1,3-indandione, is classical colorimetric reagent for detection of alpha-amino acids on paper chromatography or electrophoretograms. Primary amines and free amino acids undergo oxidative deamination and condensation with ninhydrin to produce deep purple chromophore known as Ruhemann's purple, absorbing at 570 nanometers, enabling sensitive visualization of separated amino acid bands. Secondary amines like proline yield yellow product. It does not specifically detect lipids, sugars, or intact proteins under similar conditions, though N-terminal residues may react wea
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.