A new visible light DNA fluorochrome for confocal microscopy.

We have developed a new DNA-specific fluorochrome that is excited by visible light. This chemically uncharacterized fluorochrome readily penetrates tissue in whole mounts, gives a strong signal, is inexpensive to make and very easy to use. This preparation has several advantages over existing DNA fluorochromes in confocal laser microscopy applications. Many DNA fluorochromes are excitable by ultraviolet light. These have limited utility in confocal microscopy, where commonly used lasers produce only visible wavelengths of light. Other DNA fluorochromes are available that are excitable by visible light, but some have difficulty penetrating all cell types, while others have high background or fade quickly. This new fluorochrome overcomes these problems and has an emission spectra that makes it compatible with either rhodamine or Texas Red labeled reagents for double-label experiments. The ability to label all nuclei in a tissue and make three-dimensional reconstructions by confocal microscopy is extremely useful in examining cellular distributions within specific tissues.