Surface adsorption of factor XI. II. Evidence that different mechanisms are involved in binding to glass and plastic materials.

Blood coagulation factors XI and XIa possess binding site(s) for glass and plastics, located in the heavy chain of the molecule. To elucidate the nature of binding, adsorption and desorption properties of factor XI and XIa to different surfaces have been studied. Desorption experiments with high salt (2.4 M NaC1) suggest participation of ionic forces in the binding to glass. This is consistent with the decreased adsorption of factor XI (pI-9.0) to glass with increasing pH. The non-ionic detergent Triton X-100, which splits hydrophobic bonds, desorbs factor XI very well from plastics and partially from glass. The anionic detergent SDS, which will split hydrophobic as well as ionic bonds, is the most effective agent tested for the elution of factor XI from glass. We, therefore infer, that the binding of factor XI to glass is the combined effect of ionic and hydrophobic binding, whereas the adsorption of factor XI to plastics is primarily hydrophobic.