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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 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.

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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 - ...

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