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Full-Text Articles in Physics

Sucralose Destabilization Of Protein Structure, Christina M. Othon Mar 2015

Sucralose Destabilization Of Protein Structure, Christina M. Othon

Christina M Othon

Sucralose is a commonly employed artificial sweetener that behaves very differently than its natural disaccharide counterpart, sucrose, in terms of its interaction with biomolecules. The presence of sucralose in solution is found to destabilize the native structure of two model protein systems: the globular protein bovine serum albumin and an enzyme staphylococcal nuclease. The melting temperature of these proteins decreases as a linear function of sucralose concentration. We correlate this destabilization to the increased polarity of the molecule. The strongly polar nature is manifested as a large dielectric friction exerted on the excited-state rotational diffusion of tryptophan using time-resolved fluorescence ...


The Effects Of Humidity On The Dielectric Response In Ferroelectric Polymer Films Made By Langmuir-Blodgett Deposition, Kristin Kraemer, Alexander Sorokin, Christina Othon, Stephen Ducharme, Vladimir Fridkin Jun 2011

The Effects Of Humidity On The Dielectric Response In Ferroelectric Polymer Films Made By Langmuir-Blodgett Deposition, Kristin Kraemer, Alexander Sorokin, Christina Othon, Stephen Ducharme, Vladimir Fridkin

Christina M Othon

No abstract provided.


Electron Irradiation Effects On Ferroelectric Copolymer Langmuir-Blodgett Films, Christina M. Othon, Stephen Ducharme Jun 2011

Electron Irradiation Effects On Ferroelectric Copolymer Langmuir-Blodgett Films, Christina M. Othon, Stephen Ducharme

Christina M Othon

The effect of irradiation on the ferroelectric properties of Langmuir-Blodgett films of the copolymer poly(vinylidene fluoride-trifluorethelene) is investigating using 1.26 MeV electrons with dosages from 16 to 110 Mrad. Irradiation causes a systematic decrease in the phase transition temperature, coercive field and polarization of these thin films.


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

Christina M Othon

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.


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

Christina M Othon

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

Christina M Othon

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 ...


Sub-Micron Parallel Laser Direct-Write, Christina Othon, Arnoldo Laracuente, H Ladoucuer, Bradley Ringeisen Dec 2008

Sub-Micron Parallel Laser Direct-Write, Christina Othon, Arnoldo Laracuente, H Ladoucuer, Bradley Ringeisen

Christina M Othon

We have developed a modified laser induced forward transfer (LIFT) technique which allows for the parallel deposition of hundreds of sub-micron features. The approach utilizes a self-assembled monolayer of monodisperse polystyrene microspheres as the focusing element. A monolayer of close-packed microspheres is formed on top of an ultra-thin quartz support (25 m thick), and a metallic thin film is then deposited on the underside of the quartz. This approach is different from previous parallel microsphere-assisted LIFT experiments that required the deposition of metal directly onto the surface of the periodic microsphere structure. For this study, an 800 nm, 130 fs ...


Single-Cell Printing To Form Three-Dimensional Lines Of Olfactory Ensheathing Cells, Christina Othon, Xingjia Wu, Juanita Anders, Bradley Ringeisen Dec 2007

Single-Cell Printing To Form Three-Dimensional Lines Of Olfactory Ensheathing Cells, Christina Othon, Xingjia Wu, Juanita Anders, Bradley Ringeisen

Christina M Othon

Biological laser printing (BioLP™) is a unique tool capable of printing high resolution two- and three-dimensional patterns of living mammalian cells, with greater than 95% viability. These results have been extended to primary cultured olfactory ensheathing cells (OECs), harvested from adult Sprague-Dawley rats. OECs have been found to provide stimulating environments for neurite outgrowth in spinal cord injury models. BioLP is unique in that small load volumes (~µLs) are required to achieve printing, enabling low numbers of OECs to be harvested, concentrated and printed. BioLP was used to form several 8 mm lines of OECs throughout a multilayer hydrogel scaffold ...


Jet-Based Methods To Print Living Cells, Bradley Ringeisen, Christina Othon, Jason Barron, H Young, Barry Spargo Dec 2005

Jet-Based Methods To Print Living Cells, Bradley Ringeisen, Christina Othon, Jason Barron, H Young, Barry Spargo

Christina M Othon

Cell printing has been popularized over the past few years as a revolutionary advance in tissue engineering has potentially enabled heterogeneous 3-D scaffolds to be built cell-by-cell. This review article summarizes the state-of-the-art cell printing techniques that utilize fluid jetting phenomena to deposit 2- and 3-D patterns of living eukaryotic cells. There are four distinct categories of jetbased approaches to printing cells. Laser guidance direct write (LG DW) was the first reported technique to print viable cells by forming patterns of embryonic-chick spinal-cord cells on a glass slide (1999). Shortly after this, modified laser-induced forward transfer techniques (LIFT) and modified ...


Effects Of Electron Irradiation On The Ferroelectric Properties Of Langmuir-Blodgett Copolymer Films, Christina Othon, Fred Bateman, Stephen Ducharme Dec 2004

Effects Of Electron Irradiation On The Ferroelectric Properties Of Langmuir-Blodgett Copolymer Films, Christina Othon, Fred Bateman, Stephen Ducharme

Christina M Othon

The effect of irradiation on the ferroelectric properties of Langmuir-Blodgett films of the copolymer poly(vinylidene fluoride-trifluoroethylene) was investigated using 1‐MeV electrons for doses from 0.16 to 1.10 MGy, where 1 Gray (Gy) = 100 rad. Irradiation causes a systematic decrease in the phase-transition temperature, crystallinity, and spontaneous polarization of the films. The crystallinity and spontaneous polarization of the films decreased by amounts proportional to the dose, both tending toward zero near a dose of 1.30 MGy. The ferroelectric-paraelectric phase-transition temperature, however, was only reduced by about 12%, indicating that the primary effect of irradiation was to ...