Texas Red is a red fluorescent dye , used in histology for staining cell specimens, for sorting cells with fluorescent-activated cell sorting machines, in fluorescence microscopy applications, and in immunohistochemistry . Texas Red fluoresces at about 615 nm, and the peak of its absorption spectrum is at 589 nm. Solutions can be excited by a dye laser tuned to 595-605 nm, or less efficiently a krypton laser at 567 nm. It is commonly used in molecular biology techniques like quantitative RT-PCR and cellular assays.