Water in Contact with a Cationic Lipid Exhibits Bulklike Vibrational Dynamics

Abstract

Water in contact with lipids is an important aspect of most biological systems and has been termed "biological water". We used time-resolved infrared spectroscopy to investigate the vibrational dynamics of lipid-bound water molecules, to shed more light on the properties of these important molecules. We studied water in contact with a positively charged lipid monolayer using surface-specific two-dimensional sum frequency generation vibrational spectroscopy with subpicosecond time resolution. The dynamics of the O-D stretch vibration was measured for both pure DO and isotopically diluted DO under a monolayer of 1,2-dipalmitoyl-3-trimethylammonium-propane. It was found that the lifetime of the stretch vibration depends on the excitation frequency and that efficient energy transfer occurs between the interfacial water molecules. The spectral diffusion and vibrational relaxation of the stretch vibration were successfully explained with a simple model, taking into account the Förster transfer between stretch vibrations and vibrational relaxation via the bend overtone. These observations are very similar to those made for bulk water and as such lead us to conclude that water at a positively charged lipid interface behaves similarly to bulk water. This contrasts the behavior of water in contact with negative or zwitterionic lipids and can be understood by noting that for cationic lipids the charge-induced alignment of water molecules results in interfacial water molecules with O-D groups pointing toward the bulk.

Perturbation of Hydrogen-Bonding Networks over Supported Lipid Bilayers by Poly(allylamine hydrochloride)

“…Figure 4D is consistent with this model. While we observe no significant change in OH stretching region as [salt] goes from 0.1 to 0.3 M, we observe an SFG signal intensity decrease in the CH stretching region, which we attribute to the onset of specific binding of Na + to the oxygen atoms in the lipid headgroups at these high salt concentrations, as shown by Cordomi 17 Taken together, then, it is our hope that our insights will help establishing causal relationships in nanotoxicology, and contribute to understanding, controlling, and predicting the initial steps that lead to the lysis of cells exposed to membrane disrupting polycations.…”

Structure from Dynamics: Vibrational Dynamics of Interfacial Water as a Probe of Aqueous Heterogeneity

“…For OD groups that overlap spectrally with the bend overtone (purple areas), coupling to that bend overtone allows for vibrational relaxation to occur. Reprinted with permission from ref (81). Copyright 2016 American Chemical Society.…”

“…The results were modeled (solid lines), with the model depicted in Figure 5, with energy transfer rates given by the concentration of O–D groups. Adapted with permission from ref (81). Copyright 2016 American Chemical Society.…”

“…The 2D SFG spectrum of DPTAP reveals one elongated feature along the diagonal, whereas the 2D SFG spectrum of SFG has two separate peaks along the diagonal. Adapted with permission from refs (81) and (89), respectively. Copyright 2016 and 2015 American Chemical Society.…”

Perturbation of Hydrogen Bonding Networks over Supported Lipid Bilayers by Poly (Allylamine Hydrochloride)

“…As PAH is continued to be used in nanomaterials and as thin films for biomaterials, it is important to note the toxic outcomes large quantities of PAH can have on biological systems. 17 Taken together, then, it is our hope that our insights will help establishing causal relationships in nanotoxicology, Page 11 and contribute to understanding, controlling, and predicting the initial steps that lead to the lysis of cells exposed to membrane disrupting polycations. Figure Captions.…”