SDS PAGE question

[neplina]

This question seems simple but im not sure what im missing here. The passage states that the enzyme is active as a homotetramer. It is subjected to SDS page which "confirmed the purity and showed an active band at 35 kda"

It asks for the molecular weight of the compound.

The ans is 140kDa. I thought the answer would be 35 kda because the SDS page only shows one band, so i assumed thats the combined weight of the homotetramer. Why is my reasoning flawed?

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[Matthew9Thirtyfive]

This question seems simple but im not sure what im missing here. The passage states that the enzyme is active as a homotetramer. It is subjected to SDS page which "confirmed the purity and showed an active band at 35 kda"

It asks for the molecular weight of the compound.

The ans is 140kDa. I thought the answer would be 35 kda because the SDS page only shows one band, so i assumed thats the combined weight of the homotetramer. Why is my reasoning flawed?

It’s a homotetramer. That means there are 4 parts, and they are all the same. So you are getting the weight of one of those parts. Since they are all the same, you just multiply by 4.