Hi,

Is your plasma from anticoagulated blood? I would think you have active thrombin in your plasma, which is cleaving the large amounts of fibrinogen present. Try adding direct thrombin inhibitors such as PPACK and make sure when drawing blood to use citrate (0.38% final) or heparin.

Good luck,

Steve

my plasma is aliquoted from plastic citrated tube (%3.2) 

Hi,

I assume you perform a low speed centrifugation to isolate plasma with platelets and then spin the plasma to pellet the platelets? If so, consider adding prostaglandin I2 or prostaglandin E1 as platelet inhibitors. This will prevent platelet activation and thrombin generation during your second spin. Otherwise increase your citrate concentration, consider using ACD, another common anticoagulant, or PPACK when you draw blood. If you need the ACD recipe, I will gladly send it.

Best,

Steve

To get platelet free plasma, spin at high speed (20 000 g) in polycarbonate tubes.

If you observe turbidity after thawing, it might be due to lipids, a well known peoblem in preparation of control plasa or serum.