Fusion in phospholipid spherical membranes. I. Effect of temperature and lysolecithin.

A study concerning membrane contact and fusion phenomena was made for phospholipid spherical bilayer systems with respect to temperature. Specific temperatures were obtained for the spherical bilayer membranes of phosphatidyl choline (PC) and phosphatidyl serine (PS) which indicated a greater degree of membrane fusion and were designated Tf (the fusion temperature -- PC: 43 degrees C, PS: 38 degrees C). These temperatures were reduced by about 10 degrees C for the membranes incorporated with 20% lysophosphatidyl choline. The results of the contact and fusion observed in the spherical membranes are compared and discussed with the conductance characteristics of the PC and PS planar bilayer membranes as well as dissolution study on the phospholipid monolayers formed at the air/water interface with respect to temperature. Also, a possible molecular mechanism of membrane fusion is discussed in terms of the fluidity and instability of the membrane.