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I'm a little bit confused about the influence of pH on proteins.
Increasing or lowering the ph will give the protein a net positive or net negative charge, respectively. However a lower pH or higher pH will cause the protein to denaturate --> more hydrophobic amino acids will become free to interact between different proteins --> less solubilty.

let's clarify my question
take a look at the following figure:
enter image description here


this figure indicates that a lower or higher pH then the Pi will increae the protein solubility.
However the Introduction to this article, for example, cites papers to support the following statement:

Changes in pH are shown to trigger formation of amyloid fibers and aggregation

the figure and the article are inconsistent in my opinion, so I'm definitly missing something. The first figure indicates that protein solubilty will increase when the pH becomes higher (then the pI). However the article statement indicates that an increase in pH will cause the proteins to aggregate, so lowering solubilty right?

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  • $\begingroup$ biology.stackexchange.com/questions/43149/… $\endgroup$
    – akaDrHouse
    Commented Sep 24, 2016 at 11:51
  • $\begingroup$ @akaDrHouse — Your reference is to a question to which there are no answers. This shows why people should not ignore the injunction not to use comments to provide answers. If you think the comment to that question is correct, feel free to copy and paste it as an answer. That is how StackExchange works. $\endgroup$
    – David
    Commented Sep 24, 2016 at 11:55
  • $\begingroup$ My link had a comment that was correct. A simple search in google reveals that denaturation of proteins often causes exposure of hydophobic regions, thus reducing solubility. @David perhaps that is why no more formal "answer" was needed. StackExchange also "works" to discourage one line answers, despite the fact they are often all that is needed. $\endgroup$
    – akaDrHouse
    Commented Sep 24, 2016 at 11:59
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    $\begingroup$ @akaDrHouse Yes, denatured proteins are often less soluble because of the exposed hydrophobic inner residues. However, no one has yet made a connection between a pH change and denaturation. If you (or anyone else) can find evidence of that (it may exist, I just haven't searched), please make an answer. $\endgroup$
    – MattDMo
    Commented Sep 24, 2016 at 12:55
  • $\begingroup$ @akaDrHouse — A search of Biology SE would list the previous question as unanswered. If someone chose to look at the question and read the comment they would have had no way of judging whether it was correct, as you assert, because it couldn't be voted up or down. There is a reason for the injunction you see when you open the comment box, and there is no excuse for ignoring it. $\endgroup$
    – David
    Commented Sep 24, 2016 at 12:58

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