Hyok Yoo

University of Washington

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Gerald H. Pollack

University of Washington

Federico Ienna

University of Lisbon

Ekaterina Nagornyak

University of Washington

Binghua Chai

University of Washington

Qing Zhao

Nankai University

Adam D. Wexler

Medisch Centrum Leeuwarden

Rajan K. Paranji

University of Washington

Kate Ovchinnikova

University of Washington

Jeff Magula

University of Washington

Charles E. Murry

University of Washington

Cooperative Institutions

University of Washington

Seattle University

Institute for Stem Cell Biology and Regenerative Medicine

California Institute for Regenerative Medicine

Cardiovascular Research Center

Johns Hopkins University

Johns Hopkins Medicine

Nankai University

Southeast University

Northeastern University

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Role of Proton Gradients in the Mechanism of Osmosis

The Journal of Physical Chemistry B (2009)

Qing Zhao Kate Ovchinnikova Binghua Chai Hyok Yoo Jeff Magula

Experiments were carried out to determine whether the newly identified "exclusion zone" found adjacent to hydrophilic surfaces might play a role in osmosis. Two chambers were juxtaposed face to face, separated by a membrane made of cellulose acetate or Nafion. One chamber contained water, the other 100 mM sodium sulfate solution. Osmotically driven transmembrane fluid flow from low to high salt was observed using both membranes, in agreement with previous reports. Characteristic pH differences and potential differences between chambers were also noted. Visual examination with microsphere markers revealed extensive exclusion zones adjacent to both types of membrane. As these zones routinely generate protons in the water regions beyond, unequal proton concentrations in the respective chambers may be responsible for creating both the pH and potential gradients, which may be ultimately responsible for the osmotic drive.

Osmosis

10.1021/jp9021568

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Citations (22)

Mechanism of attraction between like-charged particles in aqueous solution

Soft Matter (2009)

Ekaterina Nagornyak Hyok Yoo Gerald H. Pollack

Although it has been long known that like-charged particles attract one another in aqueous media, the mechanism underlying this counter-intuitive phenomenon has remained controversial. We tested the hypothesis put forth long ago by Langmuir and again by Feynman and by Ise, that the attraction between like-charged entities lies in an intermediate of unlike charges. Tests were facilitated by the observation that the attractive forces could be confirmed between widely separated particles of macroscopic size. Two approaches showed comparable results. In the first, pH-sensitive dyes showed intermediate zones of opposite charge: an accumulation of protons was found between negatively charged spheres, whereas between positively charged spheres the intermediate zone contained OH−groups. In the second and complementary approach, microelectrode measurements showed that in between negatively charged spheres, the electrical potential was relatively positive, whereas between positively charged spheres it was relatively negative. Hence, both approaches confirm theoretical expectations. The large number of unlike charges lying in between the like-charged spheres may come from the build-up of the recently reported "exclusion zone" surrounding each particle.

Aqueous medium

Particle (ecology)

Suspension

Aqueous suspension

10.1039/b905080a

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Citations (41)

Characteristics of Water Adjacent to Hydrophilic Interfaces

Water (2010)

Hyok Yoo David Baker Christopher Pirie Basil Hovakeemian Gerald H. Pollack

10.1201/b11671-11

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Citations (4)

Origin of the infra-red emission peak in freezing water

Indian Journal of Physics (2018)

Rainer Stahlberg Hyok Yoo Gerald H. Pollack

Supercooling

10.1007/s12648-018-1265-6

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Citations (2)

Spatially resolved evaporative patterns from water

Soft Matter (2012)

Federico Ienna Hyok Yoo Gerald H. Pollack

Unexpectedly distinct patterns in evaporation were observed over heated water. Although the patterns had chaotic aspects, they often showed geometric patterns. These patterns bore strong resemblance to the infrared emission patterns observable with a mid-infrared camera focused on the water surface. This similarity puts constraints on the mechanism of evaporation, and leads to a general hypothesis as to the nature of the evaporative process.

Similarity (geometry)

Geometric pattern

Pattern Formation

Evaporative cooler

10.1039/c2sm26497h

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Citations (11)

Spatially Resolved Evaporative Patterns from Water

arXiv (Cornell University) (2011)

Federico Ienna Hyok Yoo Gerald H. Pollack

Similarity (geometry)

Geometric pattern

Source

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Impact of Hydrophilic Surfaces on Interfacial Water Dynamics Probed with NMR Spectroscopy

The Journal of Physical Chemistry Letters (2011)

Hyok Yoo Rajan K. Paranji Gerald H. Pollack

In suspensions of Nafion beads and of cationic gel beads, NMR spectroscopy showed two water-proton resonances, one representing intimate water layers next to the polymer surface, the other corresponding to water lying beyond. Both resonances show notably shorter spin-lattice relaxation times (T1) and smaller self-diffusion coefficients (D) indicating slower dynamics than bulk water. These findings confirm the existence of highly restricted water layers adsorbed onto hydrophilic surfaces and dynamically stable water beyond the first hydration layers. Thus, aqueous regions on the order of micrometers are dynamically different from bulk water.

Confined water

Cationic polymerization

Nafion

10.1021/jz200057g

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Citations (72)

Contraction-Induced Changes in Hydrogen Bonding of Muscle Hydration Water

The Journal of Physical Chemistry Letters (2014)

Hyok Yoo Ekaterina Nagornyak Ronnie Das Adam D. Wexler Gerald H. Pollack

Protein–water interaction plays a crucial role in protein dynamics and hence function. To study the chemical environment of water and proteins with high spatial resolution, synchrotron radiation-Fourier transform infrared (SR-FTIR) spectromicroscopy was used to probe skeletal muscle myofibrils. Observing the OH stretch band showed that water inside of relaxed myofibrils is extensively hydrogen-bonded with little or no free OH. In higher-resolution measurements obtained with single isolated myofibrils, the water absorption peaks were relatively higher within the center region of the sarcomere compared to those in the I-band region, implying higher hydration capacity of thick filaments compared to the thin filaments. When specimens were activated, changes in the OH stretch band showed significant dehydrogen bonding of muscle water; this was indicated by increased absorption at ∼3480 cm–1 compared to relaxed myofibrils. These contraction-induced changes in water were accompanied by splitting of the amide I (C═O) peak, implying that muscle proteins transition from α-helix to β-sheet-rich structures. Hence, muscle contraction can be characterized by a loss of order in the muscle–protein complex, accompanied by a destructuring of hydration water. The findings shed fresh light on the molecular mechanism of muscle contraction and motor protein dynamics.

Myofibril

10.1021/jz5000879

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Citations (13)

Effect of Radiant Energy on Near-Surface Water

The Journal of Physical Chemistry B (2009)

Binghua Chai Hyok Yoo Gerald H. Pollack

While recent research on interfacial water has focused mainly on the few interfacial layers adjacent to the solid boundary, century-old studies have extensively shown that macroscopic domains of liquids near interfaces acquire features different from the bulk. Interest in these long-range effects has been rekindled by recent observations showing that colloidal and molecular solutes are excluded from extensive regions next to many hydrophilic surfaces [Zheng and Pollack Phys. Rev. E 2003, 68, 031408]. Studies of these aqueous "exclusion zones" reveal a more ordered phase than bulk water, with local charge separation between the exclusion zones and the regions beyond [Zheng et al. Colloid Interface Sci. 2006, 127, 19; Zheng and Pollack Water and the Cell: Solute exclusion and potential distribution near hydrophilic surfaces; Springer: Netherlands, 2006; pp 165−174], here confirmed using pH measurements. The main question, however, is where the energy for building these charged, low-entropy zones might come from. It is shown that radiant energy profoundly expands these zones in a reversible, wavelength-dependent manner. It appears that incident radiant energy may be stored in the water as entropy loss and charge separation.

Radiant energy

10.1021/jp908163w

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Citations (172)

Spatially Resolved Evaporative Patterns from Water

arXiv (Cornell University) (2011)

Federico Ienna Hyok Yoo Gerald H. Pollack

Similarity (geometry)

Geometric pattern

Pattern Formation

10.48550/arxiv.1112.2796

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Citations (0)