5-FAM-X, SE contains a seven-atom aminohexanoyl spacer (known as ‘X’) between the FAM fluorophore and the succinimidyl ester. The ‘X’ spacer separates the fluorophore from the biomolecule to which it is conjugated. The ‘X’ spacer may potentially reduce the quenching that typically occurs upon conjugation. We recommend this fluorescein derivative as the preferred dye for preparing fluoresceinated proteins when the fluorescence quenching of the labeling dyes by proteins is a serious problem.
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