Adsorption of phospholipids onto layered silicate surface: The case of clinochlore

The adsorption of phospholipids on clay minerals is an important research topic for both increasing the knowledge of prebiotic chemistry processes and the development of new biotechnological/pharmaceutical applications using natural components. However, atomic-scale information on the intimate relationship between lipids and clays is still missing in the scientific literature. The present work reports a detailed Density Functional Theory investigation of the adsorption of a simple phospholipid molecular model, i.e., 1, 2-divaleroyl- sn -glycero-3-phosphatidic acid (DVPA) and clinochlore, a phyllosilicate presenting an alternate stacking of hydrophobic brucite-like (B) and hydrophilic talc-like (TOT) layers. The results of the simulations, in absence of solvents and considering different surface coverages, showed that both substrates could condense DVPA, albeit with a general preference of the biomolecule for the B surface over the TOT one. Polar contacts were established between the DVPA and the substrates, originating mainly from the – PO4H2 group of the phospholipids. The presence of acidic (AlIII/SiIV substitutions) and basic (AlIII/MgII) Brønsted-Lowry sites on the TOT and B layers, respectively, deeply increased the adsorption strength between DVPA and the substrates. The obtained results, encompassing both the molecular conformation on the clinochlore surface and the molecule/substrate binding energy, provided further knowledge on the phospholipid-mineral interactions, which could be very useful to devise innovative applications in biotechnology and environmental fields.