Effect of alcohols on the collagen-phosphatidylcholine interaction

The interaction of phosphatidylcholine dispersions with acid soluble collagen separated from the skin of one month-old swine was studied to define the conditions facilitating the association of the collagen with lipids. When acid soluble collagen and phosphatidylcholine dispersions were incubated in 75 mM citrate buffer of pH 3.7 at 25 degrees C, the reisolated collagen fibrils did not contain appreciable amounts of phosphatidylcholine. However, the presence of n-propanol greatly promoted the retention of phosphatidylcholine, the amount of phosphatidylcholine associated being nearly 30% of collagen on a weight basis under optimal conditions. In contrast, methanol, ethanol, isopropanol, and n-butanol did not appreciably enhance the association of phosphatidylcholine with collagen. A limited inhibition of phosphatidylcholine retention was observed upon addition of sodium chloride to the propanol medium. The interaction of phosphatidylcholine with acid soluble collagen decreased sharply when temperature was increased above 30 degrees C; almost no phosphatidylcholine-collagen association occured at 40 degrees C. It appears that the enhanced association in the presence of n-propanol is due to a looseing of the collagen triple helix that exposes hydrophobic sites necessary for the interaction. However, the conversion of the triple helical structure to the random coil conformation by heating prevents the association of phosphatidylcholine with acid soluble collagen.