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    Net Charge of a Protein and Temperature

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    The table below indicates approximate values for these at 25C. For reference, the delta H(ionization) for Tris is 47kJ/mole.

    Group deta H (ionization)(kJ/mole)
    Asp 3.9
    Glu 0
    Lys 48
    Arg 48
    His 28
    N-term 40
    C- term 0

    How will the net charge of a typical protein change upon lowering the temperature from 37C to 4C, based on this information?

    What can be done experimentally to compensate for this?

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    Solution Preview

    Temperature has a marked effect on ionization, the extent of which depends on the heat of ionization, deltaH, of the various charged groups. In order to understand this, we need a relationship between pKa and deltaH.

    The relationship between the change in the pKa and the change in temperature is given by a derivative of the Gibbs-Helmholtz equation:

    ln(K1/K2) = (-deltaH/R)(1/T2 - ...

    Solution Summary

    This solution is provided in 285 words. It discusses ionization and how this is related to temperature. References are also included to enhance learning.