The denaturing action of lysophosphatidylcholine as studied by calorimetric and rheological techniques

The potency of lysophosphatidylcholine to perturb protein structure was investigated by differential scanning calorimetry and rheological measurements using myosin as a model protein. At physiological ionic strength (0.15 M NaCl) 5mM lysophosphatidylcholine produced a detectable reduction in the protein's enthalpy of denaturation, while concentrations less than or equal to 2 mM had no effect. At higher salt concentrations (0.6 M NaCl) lower concentrations of lysophosphatidylcholine were needed in order to reduce the enthalpy of denaturation. Also, the changes in myosin conformation, as judged from calorimetric measurements, became more extensive as the incubation temperature for myosin-lysophosphatidylcholine systems was increased from 10 degrees to 30 degrees C. Rheological techniques allowed detection of changes in the structure of filaments of myosin (in 0.15 M) upon addition of 0.2 mM lysophosphatidylcholine. The denaturing action of lysophosphatidylcholine is compared to the more familiar detergent sodium dodecyl sulphate.