We isolated LDL from human plasma by ultracentrifugation followed by dialysis (we changed from PBS to NaCl) overnight. Afterwards we oxidized native LDL with CuSO4 for 24 hrs but, after oxidation at 37 degrees, the LDL is precipitated. The protocol we use runs excellent in our old lab, but not any longer in the new lab. We already checked pH values of every solution we use, we increase the amount of buffer, which is changed frequently during dialysis, but nothing helped and we really don´t know, what´s the problem.