Publications by Halil Ibrahim Okur

Lysozyme Interaction with Phospholipid Nanodroplets Probed by Sum Frequency Scattering Vibrational Spectroscopy

Sylvie Roke, Halil Ibrahim Okur, Jan Dedic, Sergey Kulik

When a nanoparticle (NP) is introduced into a biological environment, its identity and interactions are immediately attributed to the dense layer of proteins that quickly covers the particle. The formation of this layer, dubbed the protein corona, is in ge ...

AMER CHEMICAL SOC2023

Ultrasensitive Label-Free Detection of Protein–Membrane Interaction Exemplified by Toxin-Liposome Insertion

Mircea Ioan Iacovache, Matteo Dal Peraro, Sylvie Roke, Halil Ibrahim Okur, Chan Cao, Tereza Schönfeldová

Measuring the high-affinity binding of proteins to liposome membranes remains a challenge. Here, we show an ultrasensitive and direct detection of protein binding to liposome membranes using high throughput second harmonic scattering (SHS). Perfringolysin ...

2022

Hyaluronan orders water molecules in its nanoscale extended hydration shells

Sylvie Roke, Halil Ibrahim Okur, Jan Dedic

Hyaluronan (HA) is an anionic, highly hydrated bio-polyelectrolyte found in the extracellular environment, like the synovial fluid between joints. We explore the extended hydration shell structure of HA in water using femto-second elastic second-harmonic s ...

AMER ASSOC ADVANCEMENT SCIENCE2021

Lipid Melting Transitions Involve Structural Redistribution of Interfacial Water

Sylvie Roke, Filip Kovacik, Halil Ibrahim Okur, Tereza Schönfeldová

Morphological and gel-to-liquid phase transitions of lipid membranes are generally considered to primarily depend on the structural motifs in the hydrophobic core of the bilayer. Structural changes in the aqueous headgroup phase are typically not considere ...

AMER CHEMICAL SOC2021

Transient domains of ordered water induced by divalent ions lead to lipid membrane curvature fluctuations

Sylvie Roke, Orly Bagunu Tarun, Halil Ibrahim Okur

Cations influence the electrostatic, chemical and mechanical properties of lipid bilayers. Here, label-free second harmonic microscopy shows that cation-induced transient ordering of water also plays a role in driving membrane curvature fluctuations, linki ...

NATURE PUBLISHING GROUP2020

Molecular Mechanism for the Interactions of Hofmeister Cations with Macromolecules in Aqueous Solution

Sylvie Roke, Halil Ibrahim Okur

Ion identity and concentration influence the solubility of macromolecules. To date, substantial effort has been focused on obtaining a molecular level understanding of specific effects for anions. By contrast, the role of cations has received significantly ...

AMER CHEMICAL SOC2020

On the stability and necessary electrophoretic mobility of bare oil nanodroplets in water

Sylvie Roke, Hilton Barbosa De Aguiar, Saranya Pullanchery Sankara Narayanan, Halil Ibrahim Okur, Sergey Kulik

Hydrophobic oil droplets, particles, and air bubbles can be dispersed in water as kinetically stabilized dispersions. It has been established since the 19th century that such objects harbor a negative electrostatic potential roughly twice larger than the t ...

AMER INST PHYSICS2020

Membrane–Protein–Hydration Interaction of α-Synuclein with Anionic Vesicles Probed via Angle-Resolved Second-Harmonic Scattering

Sylvie Roke, Halil Ibrahim Okur, Jan Dedic

Amyloid formation of the protein α-synuclein promotes neurodegeneration in Parkinson's disease. The normal function of α-synuclein includes synaptic vesicle transport and fusion, and the protein binds strongly to negatively charged vesicles in vitro. Here, ...

2019

Determination and evaluation of the nonadditivity in wetting of molecularly heterogeneous surfaces

Francesco Stellacci, Quy Ong Khac, Sylvie Roke, Zhi Luo, Michele Ceriotti, Filip Kovacik, David Mark Wilkins, Halil Ibrahim Okur, Anna Murello

The interface between water and folded proteins is very complex. Proteins have "patchy" solvent-accessible areas composed of domains of varying hydrophobicity. The textbook understanding is that these domains contribute additively to interfacial properties ...

National Academy of Sciences2019

Specific Ion Effects at the Interface of Nanometer-Sized Droplets in Water: Structure and Stability

Sylvie Roke, Evangelia Zdrali, Halil Ibrahim Okur

The interaction of ions with interfaces influences numerous processes in chemistry, physics, and biology, while different ion species behave differently at hydrophobic or hydrophilic interfaces. Despite its importance, ion specificity and its relation to s ...

2019

Chemistry of Lipid Membranes from Models to Living Systems: A Perspective of Hydration, Surface Potential, Curvature, Confinement and Heterogeneity

Sylvie Roke, Orly Bagunu Tarun, Halil Ibrahim Okur

Lipid membranes provide diverse and essential functions in our cells relating to transport, energy harvesting and signaling. This variety of functions is controlled by the molecular architecture, such as the presence of hydrating water, specific chemical c ...

2019

The Diverse Nature of Ion Speciation at the Nanoscale Hydrophobic/Water Interface

Sylvie Roke, Evangelia Zdrali, Halil Ibrahim Okur

Many biological systems are composed of nanoscale structures having hydrophobic and hydrophilic groups adjacent to one another and in contact with aqueous electrolyte solution. The interaction of ions with such structures is of fundamental importance. Alth ...

AMER CHEMICAL SOC2019

Polyelectrolytes induce water-water correlations that result in dramatic viscosity changes and nuclear quantum effects

Sylvie Roke, Halil Ibrahim Okur, Jan Dedic

Ions interact with water via short-ranged ion-dipole interactions. Recently, an additional unexpected long-ranged interaction was found: The total electric field of ions influences water-water correlations over tens of hydration shells, leading to the Jone ...

American Association for the Advancement of Science (AAAS)2019

Temperature dependence of water-water and ion-water correlations in bulk water and electrolyte solutions probed by femtosecond elastic second harmonic scattering

Yixing Chen, Sylvie Roke, Nathan Dupertuis, Halil Ibrahim Okur

The temperature dependence of the femtosecond elastic second harmonic scattering (fs-ESHS) response of bulk light and heavy water and their electrolyte solutions is presented. We observe clear temperature dependent changes in the hydrogen (H)-bond network ...

2018

The Jones–Ray Effect Is Not Caused by Surface-Active Impurities

Sylvie Roke, Halil Ibrahim Okur, Eric Tyrode

Pure aqueous electrolyte solutions display a minimum in surface tension at concentrations of 2 ± 1 mM. This effect has been a source of controversy since it was first reported by Jones and Ray in the 1930s. The Jones–Ray effect has frequently been dismisse ...

2018

Nanoemulsions of lipid droplets - a new model lipid system

Sylvie Roke, Halil Ibrahim Okur

WILEY2018

Kinetically Stable Triglyceride-Based Nanodroplets and Their Interactions with Lipid-Specific Proteins

Sylvie Roke, Cornelis Ulrich Lütgebaucks, Halil Ibrahim Okur

2018

The molecular mechanism of nanodroplet stability

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

2018

Intermolecular headgroup interaction and hydration as driving forces for lipid transmembrane asymmetry

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

ACS2018

Hydration mediated interfacial transitions on mixed hydrophobic/hydrophilic nanodroplet interfaces

Sylvie Roke, Rüdiger Scheu, Nikolay Smolentsev, Filip Kovacik, Halil Ibrahim Okur

Interfacial phase transitions are of fundamental importance for climate, industry, and biological processes. In this work, we observe a hydration mediated surface transition in supercooled oil nanodroplets in aqueous solutions using second harmonic and sum ...

2018