Red emitting fluorogenic dye as an efficient turn-on probe for milk allergen

Development of simple, fast and non-destructive technique such as fluorescence based method for the quanti-fication of milk allergens in various dairy products is a highly rewarding task. In this contribution, a red emitting fluorogenic dye, quinaldine red (QR) is reported for the detection and quantification of a milk allergen, beta lactoglobulin (beta-LG) in milk and whey matrices, utilizing its high selectivity and sensitivity towards beta-LG. Detail spectroscopic investigation reveals that binding of QR to the hydrophobic calyx site of beta-LG protein substantially reduces the torsional agility and propensity of TICT state formation of QR, rendering the dye highly fluorescent in nature. This enables estimation of beta-LG with LOD 52.1(+/- 0.9) nM in buffer solution and 0.21(+/- 0.01) mu M in 5 % bovine milk matrix respectively. Additionally, high selectivity and sensitivity, excellent repeatability, quick response, and emission in the biologically favorable red spectral region make QR based fluorometric quantifi-cation of beta-LG a highly attractive choice. Finally, the estimated beta-LG concentrations in milk and whey matrices from fluorometric titration and densitometry methods are found to match excellently with each other, suggesting potential of QR as an efficient turn-on fluorescent probe for the quantification of beta-LG (milk allergen) in various dairy products.