The influence of serum proteins and pH on the effective amino acid concentration in tissue culture medium

Abstract Amino acid binding by calf serum proteins in Dulbecco's modified Eagle medium has been studied by an ultrafiltration method. For some of the amino acids studied, up to 20 % may be unavailable to the cell because of non-specific, reversible binding to serum proteins. The extent of binding varies over the pH range ordinarily encountered during cell growth. A method is presented by which the degree of binding may be determined. The greatest degree of binding is noted for tryptophan, arginine and lysine.