Amino consisting of positively charged amine groups covalentlyattached to a hydr

Question

Amino consisting of positively charged amine groups covalentlyattached to a hydrophobic polystyrene resin. Name two factors thataffect the separation of amino acids on such a resin. Then, foreach pair of amino acids listed below, indicated which will elutefirst at pH 7, indicating your reasoning:

acids can be separated from one another using an anion exchangeresin

a. Asp and Arg

b.Glu and Met

c. Ile and Gly

Fora.) -c.), how would your answers change if you were to do theseparation at pH 12 instead of pH 7?

Explanation / Answer

      The factor that effect theseparation of amino acids on a hydrophobic resin is the chargeitself.       This is because,hydrophobic resin has a positive charge and the amino acids alsohave a postive charge.       So, they repel eachother.       Anion exchange resin isused to separate the molecules that are negatively charged.       Hence in the separation ofthe given amino acids we use the buffers respectively.       Separation is based on thecharge the amino acids exhibit at that particular pH.       Here the isoelectric pointis taken into consideration.       a.) Aspartate is a basicamino acid that has an isoelectric point of 2.77.            Atph of 7 this exhibits a net negative charge.            Onthe other hand Arginine is a basic amino acid that has anisoelectric point of 12.48 and at pH 7 this exhibits net            positivecharge.            Whenan anion exchange resin is used the amino acid that will elute outfirst isArginine.             Thisis because, the anion exchange resin has positive charge whichrepels with the positive charge of Arginine and             iseluted out.             WhileAspartate exhibits net negative charge at pH 7 so this binds to thepositive charge of the exchanger and its             elutionis retarded.       b.) Between Glutamate andMethionine the amino acid that is eluted out first is Methionine.             AtpH 7 both these amino acids exhibit negative charges but comparingthese both Glutamate is exhibits more             negativecharge than Methionine.             Hence,Methionine is eluted out first than Glutamate.       c.) Between Isoleucine andGlycine, the amino acid that is eluted out first is Isoleucine.            Thesetwo are non-polar amino acids which exhibit negative charges at apH of 7.             ButGlycine is more negative when compared to Isoleucine at pH 7, henceits elution is retarded and Isoleucine is             elutedout first.
         There willnot be any change in the separation iwhen it is carried out atpH 12 instead of 7.          This isbecause, even at pH 12 the amino acids exhibit same charges.
          Hopeyou are satisfied with the answer.  

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