Surface Symphony: Orchestrating DPPC/DOPC Monolayer Behavior.

This study investigates the impact of environmental factors and lipid composition on the structural and morphological properties of DPPC/DOPC (1,2-Dipalmitoyl-sn-glycero-3-phosphocholine/1,2-dioleoyl-sn-glycero-3-phosphocholine) monolayers. Temperature plays a significant role in DPPC monolayer behavior; at 15°C and 20°C, DPPC exhibits liquid expanded-liquid condensed coexistence, while at 25°C, this coexistence region disappears. Divalent ions (CaCl2) enhance more compact and uniform DPPC packing compared to monovalent ions (KCl), reducing mean area per molecule. The incorporation of DOPC into DPPC at 20°C increases the monolayer fluidity, disrupting the DPPC domain formation. For all systems, increasing surface pressure improves surface coverage and transforms micro domains into compact and continuous films at higher pressures. These findings highlight the critical roles of ionic interactions, temperature, and lipid composition in modulating lipid monolayer properties.