Interfacial Self-Assembly of Sugars at Nanoscale Membranes Leads to Micron-Scale, Spectroscopically Ice-Like Chiral Suprastructures of Water.

Life requires chemical chiral specificity. The emergence of enantioselectivity is unknown but has been linked to diverse scenarios for the origin of life, ranging from an extraterrestrial origin to polarization-induced effects, and magnetic field-induced mineral templating. These scenarios require an originating mechanism and a subsequent enhancement step, leading to widespread chiral specificity.

Finite Volume Effects in Water Nanodroplets: A Molecular Level Investigation.

Aqueous interfaces are responsible for a plethora of processes. At the nanoscale, interfaces are overwhelmingly influenced by finite volume effects that are thought to impact both molecular level and macroscopic properties. Here, finite volume effects are investigated using electrophoretic mobility and vibrational sum frequency scattering of water nanodroplets in oil and oil nanodroplets in water, made from the same chemicals.

Liposomes and Lipid Droplets Display a Reversal of Charge-Induced Hydration Asymmetry.

The unique properties of water are critical for life. Water molecules have been reported to hydrate cations and anions asymmetrically in bulk water, being a key element in the balance of biochemical interactions. We show here that this behavior extends to charged lipid nanoscale interfaces.

Charge transfer across C-H⋅⋅⋅O hydrogen bonds stabilizes oil droplets in water.

The hydrophobic–water interface plays a key role in biological interactions. However, both the hydrophobic–water interfacial molecular structure and the origin of the negative zeta potential of hydrophobic droplets in water are heavily contested. We report polarimetric vibrational sum-frequency scattering of the O–D and C-H stretch modes of 200-nanometer hexadecane oil droplets dispersed in water.

Zn Binds to Phosphatidylserine and Induces Membrane Blebbing.

Herein, we show that Zn binds to phosphatidylserine (PS) lipids in supported lipid bilayers (SLBs), forming a PS-Zn complex with an equilibrium dissociation constant of ∼100 μM. Significantly, Zn binding to SLBs containing more than 10 mol % PS induces extensive reordering of the bilayer. This reordering is manifest through bright spots of high fluorescence intensity that can be observed when the bilayer contains a dye-labeled lipid.

Introduction of Positive Charges into Zwitterionic Phospholipid Monolayers Disrupts Water Structure Whereas Negative Charges Enhances It.

The interfacial water structure and phosphate group hydration of 1,2-dioleoyl- sn-glycero-3-phosphatidylcholine monolayers were investigated at air/water interfaces. Both vibrational sum frequency spectroscopy (VSFS) and Langmuir monolayer compression measurements were made. The PC lipids oriented water molecules predominantly through their phosphate-choline (P-N) dipoles and carbonyl moieties.

Multistep Interactions between Ibuprofen and Lipid Membranes.

Ibuprofen (IBU) interacts with phosphatidylcholine membranes in three distinct steps as a function of concentration. In a first step (<10 μM), IBU electrostatically adsorbs to the lipid headgroups and gradually decreases the interfacial potential. This first step helps to facilitate the second step (10-300 μM), in which hydrophobic insertion of the drug occurs.

Plexcitons: The Role of Oscillator Strengths and Spectral Widths in Determining Strong Coupling.

Strong coupling interactions between plasmon and exciton-based excitations have been proposed to be useful in the design of optoelectronic systems. However, the role of various optical parameters dictating the plasmon-exciton (plexciton) interactions is less understood. Herein, we propose an inequality for achieving strong coupling between plasmons and excitons through appropriate variation of their oscillator strengths and spectral widths.

What Is the Preferred Conformation of Phosphatidylserine-Copper(II) Complexes? A Combined Theoretical and Experimental Investigation.

Phosphatidylserine (PS) has previously been found to bind Cu in a ratio of 1 Cu ion per 2 PS lipids to form a complex with an apparent dissociation constant that can be as low as picomolar. While the affinity of Cu for lipid membranes containing PS lipids has been well characterized, the structural details of the Cu-PS complex have not yet been reported. Coordinating to one amine and one carboxylate moiety on two separate PS lipids, the Cu-PS complex is unique among ion-lipid complexes in its ability to adopt both cis and trans conformations.

The complex nature of calcium cation interactions with phospholipid bilayers.

Understanding interactions of calcium with lipid membranes at the molecular level is of great importance in light of their involvement in calcium signaling, association of proteins with cellular membranes, and membrane fusion. We quantify these interactions in detail by employing a combination of spectroscopic methods with atomistic molecular dynamics simulations. Namely, time-resolved fluorescent spectroscopy of lipid vesicles and vibrational sum frequency spectroscopy of lipid monolayers are used to characterize local binding sites of calcium in zwitterionic and anionic model lipid assemblies, while dynamic light scattering and zeta potential measurements are employed for macroscopic characterization of lipid vesicles in calcium-containing environments.

Unquenchable Surface Potential Dramatically Enhances Cu(2+) Binding to Phosphatidylserine Lipids.

Herein, the apparent equilibrium dissociation constant, K(Dapp), between Cu(2+) and 1-palmitoyl-2-oleoyl-sn-glycero-3-phospho-l-serine (POPS), a negatively charged phospholipid, was measured as a function of PS concentrations in supported lipid bilayers (SLBs). The results indicated that K(Dapp) for Cu(2+) binding to PS-containing SLBs was enhanced by a factor of 17,000 from 110 nM to 6.4 pM as the PS density in the membrane was increased from 1.