I just tried TUNEL staining on my own for the first time. I previously got it to work perfectly, partially assisted by my PI. This time there was no staining except along one edge of the slide. Also, after I removed the slide from the humidified chamber, it was warped. Is it possible this would cause the stain to not set properly on the cells? I did have difficulty getting the cover slip to stay because of the warping. Has anyone had this problem or know how to fix it? Thanks.