Thorne Phosphatidylserine (Formerly Iso-Phos) 60cThorne Phosphatidylserine (Formerly Iso Phos) improves cell communication to support brain function, memory, focus, and modulates cortisol during stress. Phosphatidylserine is the primary phospholipid in brain cell membranes. Other mechanisms of action include enhancing cell metabolism (such as glucose utilization) and neurotransmitter formation. Phosphatidylserine also has antioxidant activity, which would protect brain cells from free radicals.