Thermo Fisher, A16302, Alexa Fluor™ 420 NHS Ester (Succinimidyl Ester)

Quantity: 100 μg
Unit Size: Each
Typical conjugation reactionAmine-reactive Alexa Fluor 420 NHS Ester can be conjugated with virtually any protein, antibody, or peptide. The reaction can be scaled for any amount of protein, but the concentration of the protein should be at least 2 mg/mL for optimal results. We recommend trying three different degrees of labeling, using three different molar ratios of the reactive reagent to protein.Alexa Fluor 420 NHS Ester is typically dissolved in high-quality, anhydrous dimethylsulfoxide (DMSO) (Cat. No. D12345), and the reaction is carried out in 0.1–0.2 M sodium bicarbonate buffer, pH 8.3, at room temperature for 15 minutes. Because the pKa of the terminal amine is lower than that of the lysine epsilon-amino group, more selective labeling of the amine terminus may be achieved using a buffer closer to neutral pH.Conjugate purificationLabeled antibodies are typically separated from free Alexa Fluor dye using a gel filtration column, such as those included in the Antibody Labeling Flex Kit for 0.5-1 mg of antibody (Cat. No. A88072).