Effects of proteins on the thermotropic phase transitions of phospholipid membranes

Interaction study of three overlapping synthetic peptides belonging to E2 protein of GBV-C/HGV with liposomes as biomembrane models

“…Therefore, electrostatic forces seem to play an important role in the observed by DSC interactions between the synthetic E2 peptides and the studied phospholipids.In summary, the synthetic GBV-C/HGV E2 peptides incorporate into DMPG lipid bilayers perturbing the packing of lipids and affecting their thermotropic properties. From our results and according Papahadjopoulos et al [6], it is tentatively suggested that the studied peptides preferentially locate at the outer regions of the bilayer extending the interactions to the polar headgroups followed by a partial penetration and deformation of the bilayer. In conclusion, this study has revealed that the extension of the perturbation effect of the peptides was related with the chain length as well as with the net charge of E2 HGV/GBV-C peptides.…”

Chemical properties of lipids strongly affect the kinetics of the membrane-induced aggregation of α-synuclein

“…In this study, we describe how the binding of α-synuclein to negatively charged membranes induces lipid segregation into protein-poor and protein-rich populations whose melting temperatures are 41 and ∼25°C, respectively. Although the binding of peripheral proteins to membranes can induce a progressive change in their T m value with increasing protein concentration (12,13), such a segregation of lipids into populations with distinct properties has previously also been observed for the antimicrobial peptide peptidyl-glycylleucinecarboxyamide (PGLa) binding to negatively charged model membranes [1,2-dimyristoyl-sn-glycero-3-phospho-(1′-rac-glycerol) (DMPG), 1,2-dipalmitoyl-sn-glycero-3-phospho-(1′-rac-glycerol) (DPPG) and 1,2-distearoyl-sn-glycero-3-phospho-(1′-rac-glycerol) (DSPG)], which in that case led to the formation of a phase with higher T m because of the stabilization of an interdigitated gel phase (40). By contrast, our CD and DSC results suggest that α-synuclein binding stabilizes the fluid phase formed by negatively charged lipids.…”

“…As some examples, the standard change in free energy of transfer of a lipid molecule from water into a bilayer (i.e., its solubility in water), the melting temperature, and the enthalpy of melting have all been found to be proportional to the number of aliphatic carbons in the hydrophobic chain, which ranges from 8 to 18 (11). In addition, the adsorption and partitioning of small molecules and proteins to membranes can also affect the structural and thermotropic properties of the latter, and the magnitude and characteristics of these changes depend on the nature of the molecular interactions (e.g., electrostatic, hydrophobic) (12,13).…”

EPR studies on model membranes of phospholipid and outer membrane proteins of Proteus mirabilis

“…1 A,B). This could be an indication that the fluidity effect was to a large extent a surface phenomenon, analogous to the type 2 interaction of phospholipid and protein in bilayers as proposed [9]. The type 2 interaction results in an increase in fluidity of membranes through binding of protein to the surface of phospholipid bilayers, with partial penetration of the protein and subsequent deformation of the bilayer.…”