Fluorescein PEG Aldehde (FITC-PEG-CHO) is one of Nanocs' reactive fluorescent PEG dyes that can react with N-terminal amines. Fluorescein is a bright green fluorescent dye with excitation/emission wavelength at 495 nm/515 nm. Aldehyde group is reactive toward amines, hydrazide or oxyamine groups from pH 5-9. Unlike amine reactive succinimidyl ester group (NHS), aldehyde can react with N-terminal amine groups at acidic pH, a condition sometimes required for certain bioconjugation reactions. Aldehyde reacts with amine group to form an intermediate Schiff bond. Further reduction with hydride will form a stable C-N bond. Reaction between aldhyde and other groups allows site-specific conjugation and labeling of fuorescein dyes to desired position on targeted molecules. Conjugated FITC dye can be easily detected by common fluorescent instruments under FITC channel. PEG linker between FITC and aldehyde offers higher water solubility, less steric hindrance and enhanced stability. Compared to other commonly used fluorescent dyes, Nanocs pegylated fluorescent dyes are more stable and easier to use.