SDS-PAGE - did not find the protein band what I expect (Jul/14/2006 )

Hi all,
I was trying to figure out if my expected protein was expressed. The molecular weight is about 32 KD. dimer.
I run the SDS-PAGE, But I did not find the protein band around 33KD(on the marker)
Basically, I just broke the cell through the ultrasonocation, and extract the protein, I did not do more purification.
My question is: I did not find the protein band, is that because the protein is too diluted in the solution?
the second question: Since the protein is dimeric, should I try to find the band around 16KD? or both 32KD and 16KD?

thank you for your help,

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How about control host cell extract from cell before induction? did you run one lane next to your expression sample? You should see a new band in your sample lane if expression is sucessful.

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1. If there is no appreciable difference between the uninduced and induced lanes, you have so little expression, you'll need to think of another way to visualise it (to see if it's expressing at all), such as a Western. Do you have an antibody to the protein, or to a tag?
2. If the protein is 16 kDa as the monomer, and if your have fully denatured and reduced it, you should see the bend at 16 kDa.

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What are you doing? coomassie stain gel, or western-blot?
what do you mean by I did not find the protein band around 33 kD (on the marker)
Do you mean that you don't see the marker? Then it would be a problem of migration or transfer.
You have to tell more.

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