Structural Inhomogeneity of Interfacial Water at Lipid Monolayers Revealed by Surface-Specific Vibrational Pump− Probe Spectroscopy (original) (raw)
Related papers
Interfacial Water Facilitates Energy Transfer by Inducing Extended Vibrations in Membrane Lipids
The Journal of Physical Chemistry B, 2012
We report the complete assignment of the vibrational spectrum of dipalmitoylphosphatidylcholine (DPPC), which belongs to the most ubiquitous membrane phospholipid family, phosphatidylcholine. We find that water hydrating the lipid headgroups enables efficient energy transfer across membrane leaflets on sub-picosecond time scales. The emergence of spatially extended vibrational modes upon hydration, underlies this phenomenon. Our findings illustrate the importance of collective molecular behavior of biomembranes and reveal that hydrated lipid membranes can act as efficient media for the transfer of vibrational energy.
Vibrational Spectroscopic Studies to Elucidate the Structure of Water at Biological Interfaces
2015
In biological systems, water takes up to 80% of the volume inside a cell. This water solubilizes the biological macromolecules such as the DNA, proteins and lipids. Recent advancements have shown that the water at the interface of a lipid membrane is structured, as five layers of structured water have been found at this solvent cage. Steady state Raman spectroscopy of water in lipids was performed in an attempt to elucidate the structure of water at the biological interface. Deuterium oxide (heavy water) was employed to hydrate lipid biomolecules. The heavier deuterium atom shifts the molecular vibrations and renders them distinct from conventional OH vibrations. Raman spectroscopy was used to probe the difficulties of observing the vibrational signature of the water molecule at low hydration limits. It was demonstrated that Raman can identify signatures of potential structured forms of water at the interface with lipid membranes.
Water vibrations have strongly mixed intra- and intermolecular character
Nature chemistry, 2013
The ability of liquid water to dissipate energy efficiently through ultrafast vibrational relaxation plays a key role in the stabilization of reactive intermediates and the outcome of aqueous chemical reactions. The vibrational couplings that govern energy relaxation in H2O remain difficult to characterize because of the limitations of current methods to visualize inter- and intramolecular motions simultaneously. Using a new sub-70 fs broadband mid-infrared source, we performed two-dimensional infrared, transient absorption and polarization anisotropy spectroscopy of H2O by exciting the OH stretching transition and characterizing the response from 1,350 cm(-1) to 4,000 cm(-1). These spectra reveal vibrational transitions at all frequencies simultaneous to the excitation, including pronounced cross-peaks to the bend vibration and a continuum of induced absorptions to combination bands that are not present in linear spectra. These observations provide evidence for strong mixing of int...
Nature communications, 2015
Because of strong hydrogen bonding in liquid water, intermolecular interactions between water molecules are highly delocalized. Previous two-dimensional infrared spectroscopy experiments have indicated that this delocalization smears out the structural heterogeneity of neat H2O. Here we report on a systematic investigation of the ultrafast vibrational relaxation of bulk and interfacial water using time-resolved infrared and sum-frequency generation spectroscopies. These experiments reveal a remarkably strong dependence of the vibrational relaxation time on the frequency of the OH stretching vibration of liquid water in the bulk and at the air/water interface. For bulk water, the vibrational relaxation time increases continuously from 250 to 550 fs when the frequency is increased from 3,100 to 3,700 cm(-1). For hydrogen-bonded water at the air/water interface, the frequency dependence is even stronger. These results directly demonstrate that liquid water possesses substantial structu...
The Journal of Chemical Physics, 2011
Vibrational dynamics of the bending mode of water interacting with ions We studied the vibrational relaxation dynamics of bending mode (ν 2 ) of H 2 O water molecules in the presence of different salts (LiCl, LiBr, LiI, NaI, CsI, NaClO 4 and NaBF 4 ). The linear and nonlinear spectra of the bending mode show distinct responses of water molecules hydrating the anions. We observe that the bending mode of water molecules that are hydrogen-bonded to an anion exhibit much slower relaxation rates (T 1 ∼1 ps) than water molecules that are hydrogenbonded to other water molecules (T 1 =400 fs). We find that the effect of the anion on the absorption spectrum and relaxation time constant of the water bending mode is not only determined by the strength of the hydrogen-bond interaction but also by the shape and structure of the anion.
Angewandte Chemie (International ed. in English), 2016
Interfacial water in the vicinity of lipids plays an important role in many biological processes, such as drug delivery, ion transportation, and lipid fusion. Hence, molecular-level elucidation of the properties of water at lipid interfaces is of the utmost importance. We report the two-dimensional heterodyne-detected vibrational sum frequency generation (2D HD-VSFG) study of the OH stretch of HOD at charged lipid interfaces, which shows that the hydrogen bond dynamics of interfacial water differ drastically, depending on the lipids. The data indicate that the spectral diffusion of the OH stretch at a positively charged lipid interface is dominated by the ultrafast (<∼100 fs) component, followed by the minor sub-picosecond slow dynamics, while the dynamics at a negatively charged lipid interface exhibit sub-picosecond dynamics almost exclusively, implying that fast hydrogen bond fluctuation is prohibited. These results reveal that the ultrafast hydrogen bond dynamics at the posit...
The Journal of Chemical Physics, 2009
We investigate the structure and orientation of water molecules at the water-lipid interface, using vibrational sum-frequency generation in conjunction with a maximum entropy phase retrieval method. We find that interfacial water molecules have an orientation opposite to that predicted by electrostatics and thus are likely localized between the lipid headgroup and its apolar alkyl chain. This type of water molecule is observed for phospholipids but not for structurally simpler surfactants.
Vibrational Spectroscopic Investigation of the Phase Diagram of a Biomimetic Lipid Monolayer
Physical Review Letters, 2003
The phase behavior of a biomimetic monolayer consisting of diphospholipid molecules on water is investigated using vibrational sum-frequency generation and fluorescence microscopy. In addition to the transition from the -molecularly disordered -liquid phase to the highly ordered and oriented condensed phase, a novel, extremely sharp transition is observed at low compression, which is attributed to the uncurling of the hydrophobic alkane chains upon compression.
Sum frequency vibrationnal spectroscopy of water molecules at interfaces
Annales de Physique
We present the surface vibrationnal sum frequency spectroscopy technique and we illustrate the ability of this method to analyze the properties of water at different interfaces. We stress the originality of this spectroscopy to evidence-water structure at hydrophobic interfaces and discuss the extension of the sum frequency generation spectroscopy.