Stability of vanadium(V)-protein complexes during chromatography

In order to reduce the risk of having artifacts during the separation of di fferent vanadium containing proteins with chromatographic methods, we carri ed out some stability tests for selecting the most appropriate eluting cond itions without breaking the vanadium(V)-protein binding. Therefore we inves tigated the stability of the vanadium-protein (transferrin and albumin) bin ding as function of the pH, salt molarity (NaCl, Na-acetate, NaBr, NaI, LiC l, NH+Cl and CaCl2) and hydrophobicity (acetonitrile). This was performed w ith a 48-vanadium tracer by means of batch experiments using ultrafiltratio n techniques to achieve a separation between protein bound and 'free' vanad ium. We found that there was a significant pH-dependence. Depending on the eluting salt used, the vanadium(V)-protein binding is also disrupted by a h igh salt concentration (> 0.3 mol/L). An acetonitrile concentration around 2, mol/L has the same disrupting effect.