ИСТИНА

Electric charges on the membrane surface are involved in all structural rearrangements, and the ions of the medium participate in the charge at the interface and its screening by the diffuse part of the electric double layer. Therefore, most of the experimental work with a suspension of subcellular particles and liposomes is carried by electrokinetic methods. However, these methods are not suitable for analyzing the factors influencing the dipole component of the boundary potential, which is a convenient indicator of structural changes at the membrane- electrolyte interface. It has been found in our previous data with inorganic cations and polypeptides, and these structural changes have been associated with their biochemical applications [1,2]. The dipole potential was controlled by methods applied to planar bilayer lipid membranes (BLM). It was concluded that this component depends on the position of the adsorption plane of ions, charged molecules immersed in the polar region of the membrane, on the orientation of the dipole moments associated with phospholipids and water molecules. On the other hand, Langmuir monolayers demonstrate a direct relationship between boundary potential and the interface structure, especially in the case of negatively charged phospholipids with saturated carbon tails (DMPS) at their phase transition from liquid ordered (LO) to condensed (LC) state. Recently, it was found that the intensity of X-ray radiation scattered at different small angles from the lipid monolayer is sensitive to the difference in lipid packing of these states [3] and to the polymer layer on this surface [4]. The data on the charge distribution along the normal to the surface obtained by the X-ray reflectometry method are in good agreement with its distribution in these systems simulated by methods of molecular dynamics. It allows us to clarify some of the internal details of structure rearrangement at different lateral pressure and the contribution of various structural components of the system to the electric field [3]. References: 1. Ermakov Y.A., Kamaraju K., Sengupta K., Sukharev S. Gadolinium ions block mechanosensitive channels by altering the packing and lateral pressure of anionic lipids. Biophys J. 98, 2010, 1018-1027. 2. Ermakov Yu., Kamaraju K., Dunina-Barkovskaya A., Vishnyakova K., Egorov Y., Anishkin A., Sukharev S. High-affinity Interactions of Beryllium (2+) with Phosphatidylserine Result in a Cross-linking Effect Reducing Surface Recognition of the Lipid, Biochemistry. 56, 2017, 5457-5470 3. Ermakov, Yu. A., Asadchikov, V. E., Volkov, Yu. O., Nuzhdin, A. D., Roshchin, B. S., Honkimaki, V., & Tikhonov, A. M. 2019. Electrostatic and Structural Effects at the Adsorption of Polylysine on the Surface of the DMPS Monolayer. JETP LETTERS, 109(5): 334-339. 4. Ermakov, Yu. A., Asadchikov, V. E., Roshchin, B. S., Volkov, Yu. O., Khomich, D. A., Nesterenko, A. M., & Tikhonov, A. M. 2019. Comprehensive study of the LE-LC phase transition in DMPS monolayers: surface pressure, Volta potential, X-ray reflectivity and MD modeling. Langmuir, 35: 12326-12338.