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Thread: Denaturation of proteins. Specially by heavy metals.

  1. #1 Denaturation of proteins. Specially by heavy metals. 
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    Hi all, and happy new year.

    I have a question about heavy metals, such as (hg+2, Pb+2, Ag+1, Cd+2). About how they denature proteins with regard to the change in protein charge and structure.

    I really need a source, reference online which I can get information about that. Been trawling the net, but google doesn't help me. Any links would be much appreciated.

    Thanks.


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    Quote Originally Posted by JackAnimated View Post
    Hi all, and happy new year.

    I have a question about heavy metals, such as (hg+2, Pb+2, Ag+1, Cd+2). About how they denature proteins with regard to the change in protein charge and structure.

    I really need a source, reference online which I can get information about that. Been trawling the net, but google doesn't help me. Any links would be much appreciated.

    From the Virtual Chembook:
    Heavy metal salts act to denature proteins in much the same manner as acids and bases. Heavy metal salts usually contain Hg+2, Pb+2, Ag+1 Tl+1, Cd+2 and other metals with high atomic weights. Since salts are ionic they disrupt salt bridges in proteins. The reaction of a heavy metal salt with a protein usually leads to an insoluble metal protein salt.
    (Bold mine)

    If anything is unclear or if this link does not suffice, feel free to ask more questions.


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    I think I did find that before, whats missing is how the charge of the protein has been affected. Unless I am not understanding the question properly.
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    Quote Originally Posted by JackAnimated View Post
    I think I did find that before, whats missing is how the charge of the protein has been affected. Unless I am not understanding the question properly.

    Proteins rely often on non-covalent interaction for their structure and thus their functionality.
    These salt bridges (which, as you might know, carry charges) function as "glue". However, the heavy metals also carry charges (as they are positive ions) and are attracted by these salt bridges. As such, these metals interfere with these bonds, disrupt them and cause denaturation as the "glue" is neutralized.
    "The only safe rule is to dispute only with those of your acquaintance of whom you know that they possess sufficient intelligence and self-respect not to advance absurdities; to appeal to reason and not to authority, and to listen to reason and yield to it; and, finally, to be willing to accept reason even from an opponent, and to be just enough to bear being proved to be in the wrong."

    ~ Arthur Schopenhauer, The Art of Being Right: 38 Ways to Win an Argument (1831), Stratagem XXXVIII.
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    So the salt bridges are charged, and then after denaturation by heavy metals, they have no charge?
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    Moderator Moderator Cogito Ergo Sum's Avatar
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    Quote Originally Posted by JackAnimated View Post
    So the salt bridges are charged, and then after denaturation by heavy metals, they have no charge?

    As I see it, the addition of heavy metals will increase the positive charge, as only positive ions interact with the salt bridges.
    "The only safe rule is to dispute only with those of your acquaintance of whom you know that they possess sufficient intelligence and self-respect not to advance absurdities; to appeal to reason and not to authority, and to listen to reason and yield to it; and, finally, to be willing to accept reason even from an opponent, and to be just enough to bear being proved to be in the wrong."

    ~ Arthur Schopenhauer, The Art of Being Right: 38 Ways to Win an Argument (1831), Stratagem XXXVIII.
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    The salt bridges are -ve charged before reaction with heavy metals? Then the heavy metals increase the positive charge to neutral?
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    Quote Originally Posted by JackAnimated View Post
    The salt bridges are -ve charged before reaction with heavy metals? Then the heavy metals increase the positive charge to neutral?

    If I am correct, then heavy metals do increase the positive charge of the protein,
    but the protein does not become neutral (as the overall charge of a protein also depends on the other amino acids and the chemical and physical conditions).
    "The only safe rule is to dispute only with those of your acquaintance of whom you know that they possess sufficient intelligence and self-respect not to advance absurdities; to appeal to reason and not to authority, and to listen to reason and yield to it; and, finally, to be willing to accept reason even from an opponent, and to be just enough to bear being proved to be in the wrong."

    ~ Arthur Schopenhauer, The Art of Being Right: 38 Ways to Win an Argument (1831), Stratagem XXXVIII.
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    Alright, that's clearer now. Many thanks
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