The amine-reactive Texas Red-X, SE is superior to Texas Red. It is much easier conjugated to a biomolecure with much higher conjugation yield. It can be used to create bright red-fluorescent bioconjugates with Ex/Em maxima ~595/615 nm. It contains an additional seven-atom aminohexanoyl spacer ('X') between the succinimidyl ester and the fluorophore group compared to Texas Red. This spacer helps to separate the fluorophore from its point of attachment, potentially reducing the interaction of the fluorophore with the biomolecule to which it is conjugated.