Specific ion effects in aqueous solutions are investigated at the molecular, nanoscopic and macroscopic levels. Femtosecond elastic second harmonic scattering (fs-ESHS) is used here to assess the chemical effects of ions on molecular and nanoscopic length ...

2017

The Molecular Mechanism of Nanodroplet Stability

Yixing Chen, Sylvie Roke, Evangelia Zdrali, David Mark Wilkins, Halil Ibrahim Okur

Mixtures of nano- and microscopic oil droplets in water have recently been rediscovered as miniature reaction vessels in microfluidic environments and are important constituents of many environmental systems, food, personal care, and medical products. The ...

Amer Chemical Soc2017

Beyond the Hofmeister Series: Ion-Specific Effects on Proteins and Their Biological Functions

Halil Ibrahim Okur

Ions differ in their ability to salt out proteins from solution as expressed in the lyotropic or Hofmeister series of cations and anions. Since its first formulation in 1888, this series has been invoked in a plethora of effects, going beyond the original ...

Amer Chemical Soc2017

Guanidinium can both Cause and Prevent the Hydrophobic Collapse of Biomacromolecules

Halil Ibrahim Okur

A combination of Fourier transform infrared and phase transition measurements as well as molecular computer simulations, and thermodynamic modeling were performed to probe the mechanisms by which guanidinium (Gnd(+)) salts influence the stability of the co ...

2017

The Jones-Ray Effect Reinterpreted: Surface Tension Minima of Low Ionic Strength Electrolyte Solutions are caused by Electric Field Induced Water-Water Correlations

Yixing Chen, Sylvie Roke, Halil Ibrahim Okur

The surface tension of electrolyte solutions exhibits a minimum at millimolar electrolyte concentrations and then rises with increasing concentration. This minimum, known as the Jones-Ray effect, has been hotly debated over the past 80 years. If not consid ...

Elsevier2017

Optical imaging of surface chemistry and dynamics in confinement

Sylvie Roke, Carlos Alberto Macias Romero, Halil Ibrahim Okur, Igor Nahálka

We imaged the interfacial structure and dynamics of water in a microscopically confined geometry in three dimensions and on millisecond time scales with a 3D structurally illuminated wide-field second harmonic microscope. Image contrast reports on the orie ...

American Association for the Advancement of Science2017

Interfacial Structure and Hydration of 3D Lipid Monolayers in Aqueous Solution

Yixing Chen, Sylvie Roke, Nikolay Smolentsev, Evangelia Zdrali, Halil Ibrahim Okur

Three-dimensional (3D) phospholipid monolayers at hydrophobic surfaces are ubiquitous and found in nature as adiposome organelles or in man-made materials such as drug delivery systems. However, the molecular level understanding of such monolayers remains ...

American Chemical Society2017

Intermolecular Headgroup Interaction and Hydration as Driving Forces for Lipid Transmembrane Asymmetry

Sylvie Roke, Cornelis Ulrich Lütgebaucks, Nikolay Smolentsev, Halil Ibrahim Okur

Variations between the inner and outer leaflets of cell membranes are crucial for cell functioning and signaling, drug–membrane interactions, and the formation of lipid domains. Transmembrane asymmetry can in principle be comprised of an asymmetric charge ...

American Chemical Society2016

Electrolytes induce long-range orientational order and free energy changes in the H-bond network of bulk water

Yixing Chen, Sylvie Roke, Nikolaos Gomopoulos, Carlos Alberto Macias Romero, Michele Ceriotti, Gabriele Tocci, Chung-Wen Liang, David Mark Wilkins, Halil Ibrahim Okur

Electrolytes interact with water in many ways: changing dipole orientation, inducing charge transfer, and distorting the hydrogen-bond network in the bulk and at interfaces. Numerous experiments and computations have detected short-range perturbations that ...

American Association for the Advancement of Science (AAAS)2016

Three Dimensional Nano "Langmuir Trough" for Lipid Studies

Yixing Chen, Sylvie Roke, Kailash Chandra Jena, Cornelis Ulrich Lütgebaucks, Halil Ibrahim Okur

A three-dimensional-phospholipid monolayer with tunable molecular structure was created on the surface of oil nanodroplets from a mixture of phospholipids, oil, and water. This simple nanoemulsion preparation technique generates an in situ prepared membran ...

Amer Chemical Soc2015

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