Could there be a problem in you gel casting assembly? It looks as if the dye/sample can escape from the well and move between the glass and the gel instead of going through the gel. What makes me think of this possibility is that the problematic smears a) do not have a straight "front" b) they even appear between lanes.  If it is persistent try running a gel with only the loading buffer, or loading buffer plus protein solubilisation agent minus the protein (you can run all three "conditions" on one gel) to pinpoint the nature of the problem.

Also, what are the specifics of your run? I would make sure that the gel during the run does not overheat.

Dear Dr. Vavilis,

Thanks for your  response. I prepared a yoghurt sample with same solutions and there was no problem for protein patterns, and there were no smears. I think there is not a problem in gel casting. My run conditions are 100 volt for stacking gel and 150 volt for seperating gel. There is no overheat for my gels.  

Check pH of UR sample. Run UR gel at lower amp. Prefer running gel in cold using cold buffers.

Dear Collagues,

Firstly thank you each other for your help. I figured aout this problem with applying all of your recommends. Firstly, I extracted oil from my samples with soxhlet extractor, then run the sample in an ice-water bath, and loaded half of the gel wells (there were 12 wells and I loaded 6). Now there is no artifact on my gels.

Dear Furkan,

Great that you have solved the problem. I will give you only ashort comment, i can notice that your gels are not well stained or they are over destained. So, make the staining for longer time or try to take out the gels from water of destaining earlier.