Orientation independent vibrational dynamics of lipid-bound interfacial water

Deiseroth, Malte; Bonn, Mischa; Backus, Ellen H. G.

doi:10.1039/d0cp01099e

Cited by 7 publications

(8 citation statements)

References 43 publications

(69 reference statements)

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“…This observation underlines the aforementioned asymmetry of water in response to positively and negatively charged surfaces. Interestingly, water dynamics in contact with zwitterionic lipids do not seem to be affected by the inversion of phosphate and choline (P-C versus C-P) in the headgroup 184 . The effect of the surface charge has also been observed in the case of silica, where the vibrational lifetime of H-bonded OH dramatically shortens when the surface charge increases (high pH) 185 .…”

Section: Water Structuring and Orientationmentioning

confidence: 98%

Water at charged interfaces

et al. 2021

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The ubiquity of aqueous solutions in contact with charged surfaces and the realization that the molecular-level details of water-surface interactions often determine interfacial functions and properties relevant in many natural processes have led to intensive research. Even so, many open questions remain regarding the molecular picture of the interfacial organization and preferential alignment of water molecules, as well as the structure of water molecules and ion distributions at different charged interfaces. While water, solutes and charge are present in each of these systems, the substrate can range from living tissues to metals. This diversity in substrates has led to different communities considering each of these types of aqueous interface. In this Review, by considering water in contact with metals, oxides and biomembranes, we show the essential similarity of these disparate systems. While in each case the classical mean-field theories can explain many macroscopic and mesoscopic observations, it soon becomes apparent that such theories fail to explain phenomena for which molecular properties are relevant, such as interfacial chemical conversion. We highlight the current knowledge and limitations in our understanding and end with a view towards future opportunities in the field.

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Section: Water Structuring and Orientationmentioning

confidence: 98%

Water at charged interfaces

et al. 2021

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“…Characterization of ultrafast dynamics has been varied, yet common themes have emerged from these measurements. Perhaps the most consistent of these is that water dynamics are slower at lipid membrane interfaces than they are in bulk. − This observation is not surprising, given that the membrane significantly disrupts the tetrahedral H-bond networks of water, but the extent of the disruption appears to be influenced by the headgroup structure and composition of the lipid membrane. The slowdown due to lipids has generally been interpreted as constrained motions of waters interacting with lipid headgroups; furthermore, the headgroup structure itself determines its extent.…”

Section: Model Systems and Case Studiesmentioning

confidence: 99%

“…Building on one-dimensional VSFG investigations of water orientations, , the dynamics of interfacial water have been measured with both time-resolved and two-dimensional heterodyne detected VSFG (TR-VSFG and 2D HD-VSFG, respectively), combining interface specificity and ultrafast time resolution. Tahara and co-workers found that the charge of a lipid or surfactant has a significant impact on the water dynamics as observed through spectral diffusion, which was significantly slower with anionic species compared to cationic. − Backus and co-workers determined that the slowdown is independent of the water orientation . Interestingly, water dynamics at the zwitterionic lipid interface cannot be described as a combination of cationic and anionic interfaces, suggesting that dipole–dipole interactions, − as well as H-bonding, drive interfacial dynamics .…”

Section: Model Systems and Case Studiesmentioning

confidence: 99%

“…38−40 Backus and co-workers determined that the slowdown is independent of the water orientation. 41 Interestingly, water dynamics at the zwitterionic lipid interface cannot be described as a combination of cationic and anionic interfaces, suggesting that dipole−dipole interactions, 38−40 as well as H-bonding, drive interfacial dynamics. 39 The presence of H-bond donors in the lipids impacts water dynamics, as surfactants with primary amines slow down interfacial water significantly more than similar surfactants with tertiary amines.…”

Section: Sum-frequency Generation Probes Interfacial Water Dynamicsmentioning

confidence: 99%

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Ultrafast Dynamics at Lipid–Water Interfaces

2020

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Metrics & MoreArticle Recommendations * sı Supporting Information CONSPECTUS: Lipid membranes are more than just barriers between cell compartments; they provide molecular environments with a finely tuned balance between hydrophilic and hydrophobic interactions that enable proteins to dynamically fold and self-assemble to regulate biological function. Characterizing dynamics at the lipid−water interface is essential to understanding molecular complexities from the thermodynamics of liquid−liquid phase separation down to picosecond-scale reorganization of interfacial hydrogen-bond networks. Ultrafast vibrational spectroscopy, including two-dimensional infrared (2D IR) and vibrational sum-frequency generation (VSFG) spectroscopies, is a powerful tool to examine picosecond interfacial dynamics. Two-dimensional IR spectroscopy provides a bond-centered view of dynamics with subpicosecond time resolutions, as vibrational frequencies are highly sensitive to the local environment. Recently, 2D IR spectroscopy has been applied to carbonyl and phosphate vibrations intrinsically located at the lipid−water interface. Interface-specific VSFG spectroscopy probes the water vibrational modes directly, accessing H-bond strength and water organization at lipid headgroup positions. Signals in VSFG arise from the interfacial dipole contributions, directly probing headgroup ordering and water orientation to provide a structural view of the interface.In this Account we discuss novel applications of ultrafast spectroscopy to lipid membranes, a field that has experienced significant growth over the past decade. In particular, ultrafast experiments now offer a molecular perspective on increasingly complex membranes. The powerful combination of ultrafast, interface-selective spectroscopy and simulations opens up new routes to understanding multicomponent membranes and their function. This Account highlights key prevailing views that have emerged from recent experiments: (1) Water dynamics at the lipid−water interface are slow compared to those of bulk water as a result of disrupted H-bond networks near the headgroups. (2) Peptides, ions, osmolytes, and cosolvents perturb interfacial dynamics, indicating that dynamics at the interface are affected by bulk solvent dynamics and vice versa.(3) The interfacial environment is generally dictated by the headgroup structure and orientation, but hydrophobic interactions within the acyl chains also modulate interfacial dynamics. Ultrafast spectroscopy has been essential to characterizing the biophysical chemistry of the lipid−water interface; however, challenges remain in interpreting congested spectra as well as designing appropriate model systems to capture the complexity of a membrane environment.

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“…6,7 Evidence of enhanced hydrogen bonds (HBs) established between water molecules and the phospholipid heads has been described in experimental investigations from infrared spectroscopy 7,8 and sum frequency generation. 9,10 Nonetheless, far-infrared spectroscopy has shown that resonance mechanisms entangle the motion of phospholipid bilayers with their hydration water. 11 Such complex interactions between water molecules and hydrophobic heads cause perturbations in the dynamical properties of water.…”

mentioning

confidence: 99%