Demihorvat

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Oct 1, 2013
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Does anyone know how to approach this question?

It asks: one method of isolating polypeptides and proteins from aq. extracts is freeze drying. The aq. solution of the polypeptide or protein is frozen. What procedure can be used to remove the water from the frozen sample?

I was completely lost. Thanks!
 

ready2go2

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Mar 29, 2013
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What were you lost about exactly? The questions or the answer choices?

Sublimination was the only one that made sense.

Fun fact: astronaut ice cream is made from the same process described... Lol
 
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Demihorvat

Demihorvat

5+ Year Member
Oct 1, 2013
70
14
Status
Medical Student (Accepted)
What were you lost about exactly? The questions or the answer choices?

Sublimination was the only one that made sense.

Fun fact: astronaut ice cream is made from the same process described... Lol
I think I was more confused with the answer choices given - I didn't really understand the effects that they could have.
 

ready2go2

5+ Year Member
Mar 29, 2013
364
550
Status
Medical Student (Accepted)
I think I was more confused with the answer choices given - I didn't really understand the effects that they could have.
So they take a protein and freeze it in solution. Now you have your protein stuck in ice crystals. Before you even read the answer choices you want something that is going to take your now solid water and get rid of it. What are some chemical process that will do that? You might say evaporation by heating it up to turn it into a liquid then gas or sublimation to turn it into a gas.

But it's a protein we are trying to preserve here so heating it up is not an option because that will denature it and that's obviously not good. So eliminate all options involving heat. B is eliminated.

D seems a little strange, add a salt to your frozen chunk of protein. The water will likely melt and you're back to where you started! Proteins in aqueous solution.

C seems strange as well, if you're familiar with extractions you'll know that a frozen sample is not going to do the trick, so that can't possibly be the next step.

So you're left with A, which you already knew was the answer because you thought of it before you even saw the choices!

Hope this helps, if not then it is likely that you need to go back and learn chemistry lab techniques.
 
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Demihorvat

Demihorvat

5+ Year Member
Oct 1, 2013
70
14
Status
Medical Student (Accepted)
So they take a protein and freeze it in solution. Now you have your protein stuck in ice crystals. Before you even read the answer choices you want something that is going to take your now solid water and get rid of it. What are some chemical process that will do that? You might say evaporation by heating it up to turn it into a liquid then gas or sublimation to turn it into a gas.

But it's a protein we are trying to preserve here so heating it up is not an option because that will denature it and that's obviously not good. So eliminate all options involving heat. B is eliminated.

D seems a little strange, add a salt to your frozen chunk of protein. The water will likely melt and you're back to where you started! Proteins in aqueous solution.

C seems strange as well, if you're familiar with extractions you'll know that a frozen sample is not going to do the trick, so that can't possibly be the next step.

So you're left with A, which you already knew was the answer because you thought of it before you even saw the choices!

Hope this helps, if not then it is likely that you need to go back and learn chemistry lab techniques.
Thanks a bunch! Makes a lot more sense now :)