AAMC SB C/P #64

[mkmmx14]

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Hey guys so i'm confused!

when do I know I have to take into the tetramer or dimer aspects when answering a SDS page question.

Becuase I thought I was supposed to keep the proteins in the given weights, I dont understand why I should multiply protein 2 19 kda (homodimer) by 2 when the bond is not being reduced.
PLZ HELP

 

[Hi_I'mPaul]

Hey guys so i'm confused!

when do I know I have to take into the tetramer or dimer aspects when answering a SDS page question.

Becuase I thought I was supposed to keep the proteins in the given weights, I dont understand why I should multiply protein 2 19 kda (homodimer) by 2 when the bond is not being reduced.
PLZ HELP

So you can associate non-reducing conditions with "disulfide bonds will not be reduced." So, in this example, we want to know which protein will be the smallest--since this will have highest motility. In this example, proteins 1, 3, 4 will run as monomers, while protein 2 is run as a dimer (since it is non-reducing conditions and has disulfide bonds).

A) It's a monomer so it'll stay at 32
B) you need to read CAREFULLY... 19kDa MONOMERS. This is running as a DIMER, so total weight of 38.
C) trimer of 25 kDa... runs as monomers so each monomer is around 8... from (25/3).
D) Dimer of 38... runs as monomer so each monomer is around 19... from (38/2).

C is the smallest and therefore will have the highest motility. If you do not understand this concept, I suggest doing research on SDS Page and reducing vs. non-reducing conditions.