Denaturing interaction between sickle hemoglobin and phosphatidylserine liposomes

Area of Science:

• Biochemistry
• Hematology
• Physical Chemistry

Background:

• Abnormal interactions between sickle hemoglobin (HbS) and erythrocyte membrane lipids are hypothesized to cause hemichrome deposition.
• Sickle red blood cells possess both HbS and abnormal peroxidized membrane lipids, potentially worsening pathology.

Purpose of the Study:

• To compare the interaction of HbS and HbA with phosphatidylserine (PS) liposomes.
• To investigate the role of lipid peroxidation in Hb-lipid interactions.

Main Methods:

• Comparison of oxyhemoglobin (oxyHb) interaction with dioleoyl-phosphatidylserine (PS) liposomes under low salt/pH conditions.
• Spectrophotometric analysis of absorbance changes at 412 nm.
• Fluorescence quenching experiments to study hemoglobin/lipid interactions.

Main Results:

• HbS demonstrated a 3.4-fold faster rate of oxidation on lipid compared to HbA.
• Hb-lipid interactions involved rapid electrostatic binding followed by irreversible changes.
• Lipid peroxidation by-products accelerated Hb denaturation and heme transfer to lipids.

Conclusions:

• Accelerated Hb denaturation upon contact with lipids contributes to hemichrome formation on sickle red blood cell membranes.
• The findings provide a molecular mechanism linking HbS, membrane lipids, and sickle cell disease pathogenesis.