Fig 4.
Isotherm for pure DPPC monolayer. Surface pressure (total lateral pressure) is expressed in units of milliNewtons/meter (mN/m) on the y-axis. Mean molecular area is in units of Å2 on the x-axis. The monolayer is initially compressed from high mean molecular areas. The surface pressure is constant at this point. With further compression the monolayer undergoes phase transitions, initially into a liquid expanded state during which surface pressure rises, then into a two phase coexistence region in which both liquid expanded and liquid condensed phases coexist and the surface pressure is constant, and finally into a rigid, liquid condensed phase.