Adsorption at equilibrium and binding of AmpliTaq(R) DNA polymerase (TDP) on clay minerals, two montmorillonites (W-M and Ap-M) and a kaolinite (K), were studied. Equilibrium adsorption isotherms were of the L type, and a plateau was reached with Ap-M and K, whereas no plateau was obtained with W-M. Adsorption of TDP was most rapid on W-M, maximal at pH 6 on all clays, and appeared to involve hydrophobic interactions between the clays and TDP. The amounts of TDP adsorbed and bound on the clays were higher on W-M than on Ap-M and K and occurred only on the external surfaces of the clays. Fourier-transform infrared spectra, SDS-PAGE and scanning electron microscopy of both pure TDP and the W-M-TDP complex showed the presence in the commercial TDP of microspheres (about 100 nm in diameter) of unidentified material, which could influence the adsorption-binding of TDP on clays
