a band that suppose to be 90KD shows up at 70KD!! - (Jan/13/2012 )
I have been coming a cross some unexplained blots. My target protein is suppose to be coming around 90 KD, but every time I run a WB it shows up at 70KD. I am following the general protocol for WB with very small changes. I called the company and they recommend to remove Tween from all of the buffers I am using, but this is didnt fix the problem and I am still seeing the bands at 70 KD.. any suggestion of why this is happening and how to fix it !!
size separation with sds-page is not absolute. there can be differences in the apparent molecular weight due to many factors (for one thing, sds doesn't really bind equally to all amino acids).
if your result is consistent and you are certain that you are detecting the correct protein then i wouldn't worry too much.