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Articles 1 - 10 of 10

Full-Text Articles in Physics

Hydration Dynamics At Fluorinated Protein Surfaces, Oh-Hoon Kwon, Tae Hyeon Yoo, Christina M. Othon, James A. Van Deventer, David A. Tirrell, Ahmed H. Zewail Aug 2010

Hydration Dynamics At Fluorinated Protein Surfaces, Oh-Hoon Kwon, Tae Hyeon Yoo, Christina M. Othon, James A. Van Deventer, David A. Tirrell, Ahmed H. Zewail

Division III Faculty Publications

Water-protein interactions dictate many processes crucial to protein function including folding, dynamics, interactions with other biomolecules, and enzymatic catalysis. Here we examine the effect of surface fluorination on water-protein interactions. Modification of designed coiled-coil proteins by incorporation of 5,5,5-trifluoroleucine or (4S)-2-amino-4-methylhexanoic acid enables systematic examination of the effects of side-chain volume and fluorination on solvation dynamics. Using ultrafast fluorescence spectroscopy, we find that fluorinated side chains exert electrostatic drag on neighboring water molecules, slowing water motion at the protein surface.


Valency Dependence Of Polymorphism And Polyamorphism In Dna-Functionalized Nanoparticles, Wei Dai, Chia Wei Hsu, Francesco Sciortino, Francis W. Starr Jan 2010

Valency Dependence Of Polymorphism And Polyamorphism In Dna-Functionalized Nanoparticles, Wei Dai, Chia Wei Hsu, Francesco Sciortino, Francis W. Starr

Division III Faculty Publications

Nanoparticles (NP) functionalized with single-stranded DNA (ssDNA) offer a route to custom-designed, self- assembled nanomaterials with potentially unusual properties. The bonding selectivity of DNA guarantees one-to-one binding to form double-stranded DNA (dsDNA), and an appropriate base sequence results in head-to-tail binding linking NP into networks. We explore the phase behavior and structure of a model for NP functionalized with between 3 and 6 short ssDNA through simulations of a coarse-grained molecular model, allowing us to examine both the role of the number of attached strands (valency) and their relative orientations. The NP assemble into networks where the number of NP ...


Charge Transfer Assisted By Collective H-Bonding Network Dynamics, Omar F. Mohammed, Christina M. Othon, Oh-Hoon Kwon, Ahmed H. Zewail Jul 2009

Charge Transfer Assisted By Collective H-Bonding Network Dynamics, Omar F. Mohammed, Christina M. Othon, Oh-Hoon Kwon, Ahmed H. Zewail

Division III Faculty Publications

Although there have been numerous studies of solvation, the role of solvent specific and collective interactions, especially for charge-transfer processes, remains difficult to unravel. Here, we report, using femtosecond fluorescence up-conversion and steady-state spectroscopic measurements, studies of well-designed single-sited formylperylene (FPe) in binary solvents. One of the solvents (methanol, MOH) can selectively hydrogen (H) bond to the carbonyl (C=O) site, while the other (acetonitrile, ACN) cannot, but both have similar polarity ( for MOH and for ACN). The results reveal that ultrafast charge transfer from the perylene unit to the carbonyl group of FPe is facilitated by site-specific H-bonding interactions ...


Solvation In Protein (Un)Folding: Effect Of Local And Bulk Dynamics In The Melittin Tetramer-Monomer Transition, Christina M. Othon, Oh-Hoon Kwon, Milo M. Lin, Ahmed H. Zewail May 2009

Solvation In Protein (Un)Folding: Effect Of Local And Bulk Dynamics In The Melittin Tetramer-Monomer Transition, Christina M. Othon, Oh-Hoon Kwon, Milo M. Lin, Ahmed H. Zewail

Division III Faculty Publications

Protein structural integrity and flexibility are intimately tied to solvation. Here we examine the effect that changes in bulk and local solvent properties have on protein structure and stability. We observe the change in solvation of an unfolding of the protein model, melittin, in the presence of a denaturant, trifluoroethanol. The peptide system displays a well defined transition in that the tetramer unfolds without disrupting the secondary or tertiary structure. In the absence of local structural perturbation, we are able to reveal exclusively the role of solvation dynamics in protein structure stabilization and the (un)folding pathway. A sudden retardation ...


Appearance Of A Fractional Stokes-Einstein Relation In Water And A Structural Interpretation Of Its Onset, L. Xu, F. Mallamace, Z. Yan, Francis W. Starr, S. V. Buldyrev, H. E. Stanley Jan 2009

Appearance Of A Fractional Stokes-Einstein Relation In Water And A Structural Interpretation Of Its Onset, L. Xu, F. Mallamace, Z. Yan, Francis W. Starr, S. V. Buldyrev, H. E. Stanley

Division III Faculty Publications

The Stokes–Einstein relation has long been regarded as one of the hallmarks of transport in liquids. It predicts that the self-diffusion constant D is proportional to (τ/T)−1, where τ is the structural relaxation time and T is the temperature. Here, we present experimental data on water confirming that, below a crossover temperature T× ≈ 290 K, the Stokes– Einstein relation is replaced by a ‘fractional’ Stokes–Einstein relation D ∼ (τ/T)−ζ with ζ ≈ 3/5 (refs 1–6). We interpret the microscopic origin of this crossover by analysing the OH- stretch region of the Fourier transform infrared ...


Polarizable Contributions To The Surface Tension Of Liquid Water, J. L. Rivera, Francis W. Starr, P. Paricaud, P. T. Cummings Jan 2006

Polarizable Contributions To The Surface Tension Of Liquid Water, J. L. Rivera, Francis W. Starr, P. Paricaud, P. T. Cummings

Division III Faculty Publications

No abstract provided.


Spatially Heterogeneous Dynamics And The Adam-Gibbs Relation In The Dzugutov Liquid, Yeshitela Gebremichael, M Vogel, M Bergroth, Francis W. Starr, Sharon C. Glotzer Jan 2005

Spatially Heterogeneous Dynamics And The Adam-Gibbs Relation In The Dzugutov Liquid, Yeshitela Gebremichael, M Vogel, M Bergroth, Francis W. Starr, Sharon C. Glotzer

Division III Faculty Publications

No abstract provided.


Thermodynamics, Structure, And Dynamics Of Water Confined Between Hydrophobic Plates, Francis Starr, P. Kumar, S. V. Buldyrev, N. Giovambattista, H. E. Stanley Jan 2005

Thermodynamics, Structure, And Dynamics Of Water Confined Between Hydrophobic Plates, Francis Starr, P. Kumar, S. V. Buldyrev, N. Giovambattista, H. E. Stanley

Division III Faculty Publications

No abstract provided.


Clusters Of Mobile Molecules In Supercooled Water, Nicolas Giovambattista, Sergey V. Buldyrev, H. Eugene Stanley, Francis W. Starr Jan 2005

Clusters Of Mobile Molecules In Supercooled Water, Nicolas Giovambattista, Sergey V. Buldyrev, H. Eugene Stanley, Francis W. Starr

Division III Faculty Publications

No abstract provided.


Dynamic Heterogeneities In Supercooled Water, Nicolas Giovambattista, Marco Mazza, Sergey V. Buldyrev, Francis W. Starr, H. Eugene Stanley Jan 2004

Dynamic Heterogeneities In Supercooled Water, Nicolas Giovambattista, Marco Mazza, Sergey V. Buldyrev, Francis W. Starr, H. Eugene Stanley

Division III Faculty Publications

No abstract provided.