Examples of commonly used fluorophores are fluorescein or rhodamine. Rhodamine is a protein specific fluorescent stain commonly used in fluorescence microscopy. Other historically common fluorophores are derivatives of rhodamine (TRITC), coumarin, and cyanine. The fluorophore rhodamine has been coupled onto norbonene, and reacted with tetrazine in living systems. The fluorescence intensity of rhodamine B will decrease as temperature increases. Cyclooctatetraene and cycloheptatriene are used as a triplet quencher for rhodamine 6G dye lasers. Rhodamine 123 is a chemical compound and a dye. Rhodamine dyes fluoresce and can thus be detected easily and inexpensively with fluorometers. Rhodamine B is a chemical compound and a dye. Other popular tracer dyes are rhodamine, pyranine and sulforhodamine. While in Texas, the Hauglands developed the Texas Red dye, a rhodamine derivative. Rhodamine 123 is also used in biochemistry to inhibit mitochondrion function. Similar penetration efficiency was shown for compounds with rhodamine 19, such as SkQR1. Different compounds, such as rhodamines (Rhodamine 6GD, Rhodamine B) are used for other colours. Rhodamine B is often mixed with herbicides to show where they have been used.