I use a very specialised protocol called DNA combing which demands an anti-CldU and an anti-IdU antibody that do not cross-react. The field has always used an anti-CldU rat antibody from clone BU1/75: the only verified antibody that does not cross-react on IdU in this application. Unfortunately, not all commercial sources are the same! It can currently be bought from Abcam and Novus, but both sources cross-react on IdU. Sources that did NOT were SeraLab BU1/75, Cat. MA5 250, AbD Serotec Cat. OBT 0030, and Thermoscientific (made by Invitrogen) Cat. MA-1-82088. ALL these have been tragically discontinued! This puts work using the DNA combing technique in significant jeopardy. I am appealing to any scientists who may have the antibodies listed above stored away in their freezers...