Phase separation of phospholipid multilayers incorporated with cell penetrating peptides

Abstract

We used X-ray reflectivity to investigate the structures of phospholipid multilayers with transcription-activating-factor-derived peptide ͑TDP͒ as a function of the membrane charge density. Mixed phospholipid multilayers of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine ͑DPPC͒ and 1,2-dipalmitoyl -sn-glycero-3-phosphoserine ͑DPPS͒ with different mixing ratios ͑C:S͒ were used to elucidate the various charge densities in a plasma membrane. We fixed the peptide/lipid molar ratio ͑P/L͒ and varied the DPPC/DPPS molar ratio in the mixed multilayer. In the pure DPPC multilayer, the incorporation of TDP had nearly no effect on the bilayer thickness of the mixed lipid multilayer. However, in the mixed DPPC/DPPS multilayer, the incorporation of TDP decreased the bilayer thickness, suggesting that the TDP peptide had a stronger interaction with DPPS than with DPPC and caused disorder in the lamellar structure. Combining this with the refined X-ray reflectivity ͑XR͒ data, we concluded that the TDP existed more in the headgroup region of the TDP-induced segregated DPPS in the mixed multilayer and caused significant membrane thinning.

Lamellar slippage of bilayers—A hypothesis on low friction of natural joints

“…3, the friction coefficients measured for a partial and completely depleted cartilage samples (curve 2) are compared with the results obtained for natural joints (curve 3) with healthy and naturally degenerated articular surfaces. 5,35,51,52 We interpret the increased friction coefficient values due to the number of bilayers available in SAL. 27,30,36 Both the friction and wettability show very similar behavior as the SAL thickness is varied.…”

“…44,45 A layer of hydrated water strongly binds to the negatively charge cartilage surface, and when in contact with synovial fluid components (charged biomacromolecules, PL lamellar aggregates, and liposomes), this reduces the friction between cartilage surfaces. [45][46][47][48][49][50][51][52]…”

Can adding oil control domain formation in binary amphiphile bilayers?

“…The two different types of domain that form in a binary amphiphile mixture may be in the liquid and gel phases respectively [9][10][11][12], or may both be in the liquid phase [12][13][14][15], albeit with different degrees of internal order in the amphiphile chains [4,12]. Domain formation can be controlled by a variety of factors, including the difference in chain length between the two amphiphile species [4,9,16,17], the lateral tension in the bilayer [11,18] and the presence of a third species, such as a protein or peptide [1,[19][20][21][22], cholesterol [4,10,12,20],…”

“…The two different types of domain that form in a binary amphiphile mixture may be in the liquid and gel phases respectively, [9][10][11][12] or may both be in the liquid phase, [12][13][14][15] albeit with different degrees of internal order in the amphiphile chains. 4,12 Domain formation can be controlled by a variety of factors, including the difference in chain length between the two amphiphile species, 4,9,16,17 the lateral tension in the bilayer 11,18 and the presence of a third species, such as a protein or peptide, 1,[19][20][21][22] cholesterol, 4,10,12,20 ionised calcium 23 or a ceramide. 24 In this paper, we focus on a system in which two of these factors interact, and use a coarse-grained mean-eld model to investigate how adding oil to a bilayer composed of two amphiphiles of different chain lengths affects the structure of the membrane around the boundary between two liquid domains.…”