Modulation of Interfacial Hydration by Carbonyl Groups in Lipid Membranes

Abstract

The lack of carbonyl groups and the presence of ether bonds give the lipid interphase a different water organization around the phosphate groups that affects the compressibility and electrical properties of lipid membranes. Generalized polarization of 14:0 Diether PC in correlation with FTIR analysis indicates a higher level of polarizability of water molecules in the membrane phase around the phosphate groups both below and above T m . This reorganization of water promotes a different response in compressibility and dipole moment of the interphase which is related to different H-bonding of water molecules with PO and CO groups.

Effect of cholesterol on the hydration properties of ester and ether lipid membrane interphases

“…The greater organization at the DMPC interphase, can be due to the possibility that water molecules could form an intramolecular water bridge binding simultaneously to PO and CO groups by H bonds, in the same lipid molecule forming a water bridge [13]. The MD results indicate that Chol in DMPC does not break these water bridges, but rather forms a water bridge between CO and its -OH group, giving place to a more ordered interphase region J o u r n a l P r e -p r o o f WPC index reports that the presence of water molecules without H-Bonds (000) or only one H-Bond (100) is higher for 14:0 Diether PC compared to DMPC in accordance with the increase of relaxable population observed by fluorescence analysis (Fig 4 and 6).…”

“…The water-phosphate interaction is enhanced when carbonyl groups are absent [11,12]. It has been shown using a combination of fluorescent spectroscopy, FTIR-ATR analysis and monolayer surface pressure/area isotherms that the population of relaxable water molecules is increased in ether in comparison to ester PC [13]. This has been explained by the formation of water bridges between phosphate (PO) and carbonyl (CO) groups of the PCs that hinders the rotational degrees of freedom which are gained when the water molecule is linked only to the PO in the ether lipid [13][14][15].…”

“…These two emitting states can be obtained by Log-Normal (LN) decomposition of Laurdan emission fluorescence [24,36]. These emitting states are an indirect measure of water molecules' populations with different rotational degrees of freedom surrounding Laurdan [13,24]. J o u r n a l P r e -p r o o f…”

Spectral Response of Interfacial Water at Different Lipid Monolayer Interfaces upon Interaction with Charged Gold Nanoparticles

“…In general, interfacial water present at the biological membrane possesses a more structured hydrogen bonding network compared to the bulk water. − The model lipid membrane, such as 1,2-dipalmitoyl- sn -glycero-3-phosphoglycerol (DPPG), 1,2-dipalmitoyl-3-trimethylammonium-propane (DPTAP), and 1,2-dipalmitoyl- sn -glycero-3-phosphocholine (DPPC), provides the net negative, positive, and neutral charge at the interface, respectively. A net electric charge by its nature aligns the static dipole of water molecules and dictates water molecule orientation and organization at interfaces.…”

Thermally Driven Transformation of Water Clustering Structures at Self-Assembled Monolayers

“…Water molecules are greatly important in life, especially in various life processes such as protein folding and denaturation, biomolecular hydration, membrane formation, and ligand binding. Their unusual clustering structure and specific nature are considered as the key features in signal transduction, ionic transportation, cellular lubrication, structural stabilization, response facilitation, and microscale partitioning in various life activities. − For several decades, the structures of liquid water have been puzzling in spite of numerous similar or inconsistent hypotheses and theoretical models proposed and proven by different computer simulations and experiments. − At the macroscale, the liquid water structures appear to be homogeneous and easy to measure; however, a complication at the nanoscale is that the water structures are considered to be inhomogeneously distributed and the localized and structured water clusters are connected by an infinite and dynamic hydrogen-bonded network that is strongly influenced by temperature, pressure, and the surrounding chemical groups. − Restricted to the limit in nondestructive and in situ nanoscopic observation techniques at a molecular level, there is surprisingly no consensus about the liquid water clustering structure model . One of the classic multicomponent coexistence models indicates that pure water consists of three clustering components, the multimer water [MW with a DDA (D, donor; A, acceptor) hydrogen bonding (HB) configuration] component, the intermediate water (IW with a DA HB configuration) component, and the network water (NW with a DDAA HB configuration) component, which has been demonstrated by infrared Gaussian fitting evidence. − It is worth noting that despite the lack of theoretical reasons for why the actual subpeaks should follow Gaussian fittings, they generally fit very well .…”