Differential adsorption of a membrane skeletal protein, spectrin, in phospholipid membranes

Abstract

The interaction of phospholipids with the peripheral membrane proteins like spectrin is important not only to understand the various physiological functions of cells, but also to gain insight into the mechanism involved in the self-assembly of polymer-like long chain molecules at the soft surfaces and interfaces. The lipid head-group specificity of adsorption of spectrin to supported phopsholipid bilayer model membranes has been investigated using the X-ray reflectivity (XRR) technique. Model lipid bilayers composed of phosphatidylcholine (PC) and phosphatidylethanolamine (PE) head groups have been prepared on a soft polymer cushion and the XRR measurements have been carried out from the bilayers immersed in a water bath using high-energy synchrotron X-rays. Our results suggest that in PC-based membranes the spectrin chains form a uniform layer on top of the bilayer with their chains lying on the membrane surface, while in PE-based membranes with relatively smaller head groups, the spectrin chains are attached only through a few possible binding sites with the rest of the part projected out of the membrane surface. In addition, the reflectivity profiles reveal the penetration of spectrin polypeptide chains through the PE bilayer in its fluid phase. Pressure-area isotherm measurements on Langmuir monolayers also support similar observations on the adsorption of spectrin molecules to the membranes composed of PC and PE. The observed results were explained using a qualitative model based on the ion-mediated protein interaction in the PC-based membrane.

Characterization of Monoolein Langmuir Monolayers Spread at The Salt Solution/Air Interface

“…From the experimental observation, it can be seen that the elasticity modulus is < 10 mN/m for the liquid expanded (LE) state, 10-25 mN/m for the liquid condensed (LC) state, and >25 mN/m for the solid (S) state. These experimental findings for the elasticity modulus are consistent with the results previously published [21]. Also, their LE state did not start from zero surface pressure; it decreased later, as observed in Figure 5.…”

“…Recently, elastic energy was measured with the topographical changes of lipid macromolecules using the Langmuir monolayer approach [20][21][22][23]. Similarly, several other theoretical methods were developed and used for various experiments to better understand the driving force of the folding-unfolding phase transition behavior.…”

Deciphering interactions of ionic liquids with biomembrane

“…The pressure (π)-area (A) isotherm measurement of the Langmuir monolayer is a simple technique to follow the interaction of any foreign macromolecules with the selfassembled lipid monolayer formed at the air-water interface (Maget-Dana 1999;Giri et al 2017aGiri et al , 2017bSharma et al 2017a). Recently, it has been used to investigate interaction of ILs with the phospholipid monolayer (Bhattacharya et al 2017;Sharma et al 2017a).…”

“…5a. This bilayer configuration would be stable only under water; hence, this substrate containing bilayer is transferred to a specially designed cell (Giri et al 2017a) so that the membrane always remains under water and the XRR measurements have been carried out. The layer model had been used to describe the X-ray reflectivity data, where a single layer was used to describe the whole lipid bilayer.…”

Characterization of Monoolein Langmuir Monolayers Spread at The Salt Solution/Air Interface

“…The lipid monolayer macromolecule assists in the understanding of the folding unfolding behaviour of interacting molecules along with the structural analysis of the formed monolayers [20]. The elastic energy measurement was recently carried out with the lipid macromolecules' topographical changes by the Langmuir monolayer approach [21][22][23][24]. Similarly, several other theoretical methods were developed and used for the various experiments to understand better the driving force for folding unfolding phase transition behaviour observations.…”