One of my colleagues is interested in using the nucleic acid stain Ethidium homodimer-1 (EthD-1) from Molecular Probes to label nuclei in plant cells. He needs an alternative to DAPI which we could use with an Argon (488/514) or HeNe laser for confocal work. Does anybody know how EthD-1 compares to DAPI in specificity for DNA vs. RNA, permeability, etc? Does anybody have a suggestion of another dye which would have similar specificity than DAPI but could be used with an Ar/He-Ne laser system? We would appreciate any information that anybody could make available to us, before he decides to purchase the dye (since it is pricy). Thanks in advance, Matilde M. Urrutia Dept. Biological Sciences The University of Alabama Box 870206 Tuscaloosa, AL, 35487-0206 e-mail: [log in to unmask]