protein please…

[victor]

Hey y’all…my name is Victor and this is my first post in this ‘protein please…’ topic.

Umm, I wanna ask about protein’s behavior when it reaches its isoelectric point. My assistant said that at its isoelectric point, protein will become a zwitter ion where it has both positive and negative charges. These two charges is eliminating each other and thus make the entire protein has no net charge and must’ve get precipitated to the base of the reaction tube.

Then I ask to my assistant that even though the protein has no net charge, would it still a polar compound, because it’s stated in biochemistry book that this zwitter ion is dipolar, which I take it as having two poles with antagonistic charge. if it’s still a polar compound, then it’s still soluble in the aqueous environmet.
But why that my assistant said that when the protein is neutral, then it behave like a non-polar compound and automatically behave like oil and water. Is it true?

So, simply said that, what my assistant get is that neutral protein is non-polar, so it will be repelled from its aqueous environment which is to the base of the reaction tube or to the top of the tube. But I said that it’s not like that…..so, which one is true?

Please help ASAP, it’s a "homework" question…:lol:

[MrMistery]

well, i don’t know(i haven’t read it in any book). but a little logical thinking(and an analogy to a friend of mine named glicine) tell me you are right and not your lab assistant.
here is what my friend says: my friend is a simplified version of your protein(it has one positive and one negative charge when placed in water). thus it has a net charge of 0. is my freind glicine still soluble in water? yes, according to any basic chemistry book. so, yes, i agree with you. i can’t possibly see what your assistant was thinking…

[victor]

thanks for that Andrew…at last I’ve finished my "protein II" lab assignment 😆 And now, here I come to "protein III" lab assignment, it’s about the derivatives of protein. Umm, I’ve one favor…..anyone can help me in finding some journals related to metaprotein and proteoses? 😀

Thanks in advance
Victor

[Dr.Stein]

Hey Vic, Prof Soekarti is an expert for this case. I remember she explained us long time ago in our postgraduate program. She provided a graphic on the board, unfortunately, I cannot recall what it is. You can ask her, but please don’t tell her if I told you this. She will search me. I need to hide from her 😆

[victor]

Thanks for da info Doc..:lol: okay, I’ll ask her about this, hope that she’ll help me for this… 😀

[sdekivit]

protein is still soluble in water, because it bears charge, but the overall charge is 0. The effect is not that is will be insoluble, but it won’t move anymore to a negative/positive charge on a gel with a pH-gradient as in IEF.

Note: that the overall charge, in theory, your protein doesn’t necessarily have to be a zwitter ion (but because of the pH-gradient, most are zwitterions, but these only account for 2 charges: the N-terminus and C-terminus). Also the side chains of some aminoacids can bear a charge. It is the sum of all those outward charges that determines the overall charge of the protein. (the side chains account more to the net charge of the protein!)

[victor]

okay, tanks for the explaination from y’all…:D

But, I still got some bad news…I can’t find any articles about protein derivatives which are for metaprotein and proteose for my lab report…:(
anybody can help me looking for those articles? I’d greatly appreciate it…

[Dr.Stein]

Have you done googling?

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