HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY OF AMINO-ACIDS, PEPTIDES AND PROTEINS .131. O-PHOSPHOSERINE AS A NEW CHELATING LIGAND FOR USE WITH HARD LEWIS METAL-IONS IN THE IMMOBILIZED-METAL AFFINITY-CHROMATOGRAPHY OF PROTEINS

Conditions for the immobilization of 0-phosphoserine (OPS) to epoxy-ac tivated Sepharose CL-4B are described. The binding behaviour of OPS an d iminodiacetic acid (IDA) immobilized onto Sepharose CL-4B, toward th e hard Lewis metal ions Al3+, Fe3+, Ca2+ and Yb3+, and Cu2+ ion as a b orderline metal ion control, over the pH range pH 4.0 to pH 8.0, was e xamined. Immobilized OPS shows a stronger affinity for Fe3+ and Al3+ i ons but a lower affinity for Cu2+ and Yb3+ ions, compared to immobiliz ed iminodiacetic acid (IDA), over the equilibrating range examined. Im mobilized OPS-M(n+) was screened for protein binding using as model pr oteins tuna heart cytochrome c (THCC), horse myoglobin (HMYO) and hen egg while lysozyme (HEWL) over the pH range 5.5 to 8.0. Immobilized OP S-Fe3+ bound THCC under all the examined equilibrating conditions, bou nd HMYO between pH 5.5 and pH 7.0 and did not bind HEWL under any cond ition examined. Immobilized OPS thus presents an additional mode of me tal ion and protein selectivity in immobilized-metal affinity chromato graphy.