Sulforhodamine 101 is a non-fixable red fluorescent dye used as a specific marker for astrocytes and an activity-dependent probe for monitoring regulated exocytosis. In addition to labeling astrocytes, it also labels myelinating oligodendrocytes. Has been reported to affect excitability of neurons and should therefore be used with caution. Key precursor used for preparing rhodamine 101 sulfonyl chloride (also called Texas Red). Spectral data: λex 586 nm| λem 605 nm in H2O and λex 582-588 nm| λem 601-609 nm in pH7 buffer.