The interaction of sodium, potassium, calcium, and magnesium with human serum albumin, studied by means of conductivity measurements

Abstract
To test the usefulness of conductivity measurements in the study of ion interaction with proteins, the binding of Na, K, Ca, and Mg by human serum albumin was investigated.The measurements were carried out with albumin solutions which were defined by a constant negative net charge of 36 units per albumin molecule, corresponding to a mean pH value of 7.5.No or little binding of Na and K by this protein was found. Ca and Mg were bound to a maximum of about 8 ions per albumin molecule. This maximum corresponds to only a fraction of the net initial charge. The results are in agreement with those of other workers.The method proved to be of value for simple, well‐defined systems and has the advantage that all the difficulties encountered in the use of membranes and potential measurements are avoided.Moreover, it may be used when only small amounts of protein are available.

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