I have a problem with my 2D SDS-PAGE. There are pattern distorsion in my gels - it seems that spots (less than about 30 kDa) make "waves" (but not all gels have this problem in spite of the same experimental conditions).
There are some pictures:



Don't you have any idea what the problem is? Thank you for your advice.
Experimental condition:
sample - depleted plasma (7 most abundat proteins except fibrinogen), desalted, concentrated
strips equilibration overnight (with sample), after first dimension 20 + 20 min equil. with DTT and iodoacetamide
second dimension (gradient gels 5-15%), 30 mA/gel, about 1 hour runnig
Coomassie blue staining













