Separation of carboxylic acids by SDS electrophoresis

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MyNameIsRobertPaulson

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Hi all, came across a practice question that gave me 3 carb. acids with overlapping boiling points and asked me to pick which was bets way to separate them all.


A. extraction separation using aqueous KOH.

B. HPLC with polar solvent.

C. fractional distillation.

D. SDS electrophoresis.


They say the answer is D, because the acids are only meaningfully different in their molecular weights/size, which SDS-PAGE can exploit. I know this is used to separate AA chains and nucleic acids, but can you use it to separate individual acids from one another? would the answer need to say the pores are sufficiently small?

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I thought SDS implied using a detergent to unfold amino acid chains. Does the question say anything about a chain or structure, or give an idea what the carboxy groups are attached to?

Electrophoresis by itself will move the similarly shapes/charged molecules similar distance, with the distance between them growing larger the longer you run the electric field. Those other molecules you mentioned- AA chains and nucleic acids- are much larger than individual amino acids, though are far as pore size generally we run the nucleic acids in a agarose gel, with the page gels being more for protein chains, unfolded by SDS. Be careful with wording, your question uses "carboxy acid" and you are saying "amino acid", the carboxy groups could be on something like an aspirin molecule, completely unrelated to amino acids.
 
I thought SDS implied using a detergent to unfold amino acid chains. Does the question say anything about a chain or structure, or give an idea what the carboxy groups are attached to?

Electrophoresis by itself will move the similarly shapes/charged molecules similar distance, with the distance between them growing larger the longer you run the electric field. Those other molecules you mentioned- AA chains and nucleic acids- are much larger than individual amino acids, though are far as pore size generally we run the nucleic acids in a agarose gel, with the page gels being more for protein chains, unfolded by SDS. Be careful with wording, your question uses "carboxy acid" and you are saying "amino acid", the carboxy groups could be on something like an aspirin molecule, completely unrelated to amino acids.

No, just 4 Carboxylic acids though it does show their structure. I used amino acid b/c I know that SDS-PAGE can separate nucleic acids and amino acid chains (peptides, proteins) based on size but THIS Q implies one can use the process to separate random carboxylic acids from eachother. In principle I guess it could work but I don't know electrophoresis that well so I thought I'd ask.

Thanks for the reply!
 
I would say that since they are carboxylic acids with different boiling points and SDS is used to disrupt non-covalent bonds, then it would seem to me that it is fitting since boiling point can be altered by numerous bonds within the system.
 
Fractional distillation is the correct way. Where'd you get the question from?
 
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