Does anyone recommend a ladder with a range that encompasses 30kd to 200kd? The one I've been using does not show up in my image. After electrophoresis, I transfer the proteins to nitrocellulose and my secondary is anti-rabbit HRP. I add super signal just before imaging with a UVP system. The ladder than I use does not show up in the image but it did when I used PVDF, ECL, and a typhoon imager. Interestingly, this ladder only reacts with one of my primary antibodies and that's it. Not sure what is going on! Thanks!