protein degradation - (Nov/17/2010 )

how can we deduce that our protein extract is degradated from western blot images.
i did WB on samples from brain tissue, that was in -20°C since 2 or 3 months, and some 1 week.
i saw different profile on my filter after w.b. the signal is lower in the samples kept 3months in -20°C. morever, there are some bands at the top of the filter. but may be this is due to aspecifics because of secondary antibody..
if u have ideas about this topic, thanks for your interaction

the bands at the top of the membrane may be due to aggregation of the antigen. this may account for the reduced signal at the normal migration distance.

If the protein is degraded, you will see bands (or smears) at smaller molecular weights

its what i see in my western!
smears in below!! so, i think its my samples which are degradated.