Abstract
Dynamic behavior during the drying process of phospholipid multilayers composed of 1,2-dipalmitoyl- sn-glycero-3-phosphocholine and 1,2-dihexadecanoyl-sn-glycero-3-phospho-(10-rac-glycerol) in mixtures of 1:4, was investigated by means of attenuated total reflection (ATR) Fourier transform infrared spectroscopy (FTIR). The interaction of the antimicrobial peptide halictine-1 (HAL-1), a linear dodecapeptide isolated from the venom of eusocial bee Halictus sexcinctus, with the lipid layer and its influence on the dynamics of the lipid layer was also studied.
Analysis of ATR-FTIR spectra of the drying process by principal component analysis (PCA) clearly showed the sensitivity of C=O vibrations at 1737 cm(-1), PO2 vibrations in the region 1000-1250 cm(-1) and CH stretching vibrations at 2850 and 2950 cm(-1) to the hydration of the lipid layer. Nevertheless, PCA revealed that the lipid layers periodically oscillate between dehydration/hydration states.
The protective influence of HAL-1 on the lipid layer, including the disappearance of dehydration/hydration oscillations, and slowing down of the drying of the system in the presence of the peptide was observed. PCA indicates a two-stage process of the interaction of HAL-1 with lipid layers and as well as the influence of HAL-1 on vibrations of the C=O and PO(2) of lipid groups, whereas CH(2) and CH(3) vibrations remain intact during the binding of the peptide.
The peptide binds to phospholipid head groups, changes its structure from a random coil to an alpha-helix structure, and interacts with the C=O groups of the lipids, staying on the surface of the membrane.