Joan E Curry
Associate Department Head, Environmental Science
Member of the Graduate Faculty
Professor, BIO5 Institute
Professor, Environmental Science
Primary Department
(520) 626-5081
Research Interest
Joan Curry, PhD, stands in the field of research related to interfacial chemistry, which is a focus within physical chemistry. Within interfacial chemistry, she focuses on chemistry of molecules at the interfaces where solids and liquids come together. The term solid here includes mineral and bacterial surfaces found in soils and sediments, metal and oxide machine surfaces and cell surfaces found in the human body. Molecules can be water and ions that bathe soil surfaces, organics that lubricate machine parts and large biomacromolecules, such as proteins and lipopolysaccharides, attached to cells that mediate cell adhesion. Her specific interests are: 1) determining the effect of confinement on liquids in general and lubricants in particular and 2) characterizing the adhesive properties of cell surface biomacromolecules. The primary goal of this work is to understand how biomacromolecules that cover cell surfaces influence the interaction and adhesion of cells with other cells and with solid surfaces. Cells can be either bacteria or human cells. It is important to understand bacterial adhesion because it is the first step in biofilm formation, which has numerous undesirable consequences ranging from heat exchanger fouling to medical implant infections. Currently, very little is known about how bacterial surface biomacromolecules mediate adhesion and therefore it is still not possible to control or manipulate the process. Human cell adhesion is also mediated by biomacromolecules, in particular proteins that bind to one another through specific lock and key mechanisms. The structure of many cell adhesion proteins is well known but their function is still poorly understood. In collaboration with Ronald Heimark (Surgery), Dr. Curry is working to understand how heavy metals such as cadmium affect the binding of cell adhesion proteins called cadherins. This work will help scientists understand better how heavy metals may lead to birth defects and in adults could accelerate cardiovascular disease. This work is experimental and involves direct force measurements between biomembrane covered mica surfaces with the Surface Forces Apparatus (SFA). With the SFA it is possible to measure the magnitude and distance dependence of molecular forces acting between two flat surfaces with angstrom and nanonewton resolution.

Publications

Zhen, S. u., Cushman, J. H., & Curry, J. E. (2003). Computer simulation of anisotropic diffusion in monolayer films in mica slit pores. Journal of Chemical Physics, 118(3), 1417-1422.

Abstract:

Molecular dynamics and grand canonical Monte Carlo simulations were conducted in order to understand better the relationship between the diffusion of octamethylcyclotetrasiloxane (OMCTS) and cyclohexane monolayers and the atomic structure of confining mica surfaces. It was found that diffusion increases with reduced fluid density. With the surface separation just large enough to accommodate a monolayer, lateral diffusion was direction dependent due to the influence of the atomically structured surfaces.

Curry, J. E., Zhang, F., Cushman, J. H., Schoen, M., & Diestler, D. J. (1994). Transient coexisting nanophases in ultrathin films confined between corrugated walls. The Journal of Chemical Physics, 101(12), 10824-10832.

Abstract:

Grand-canonical Monte Carlo and microcanonical molecular dynamics methods have been used to simulate an ultrathin monatomic film confined to a slit-pore [i.e., between solid surfaces (walls)]. Both walls comprise atoms rigidly fixed in the face centered cubic (100) configuration; one wall is smooth on a nanoscale and the other is corrugated (i.e., scored with regularly spaced rectilinear grooves one to several nanometers wide). Properties of the film have been computed as a function of the lateral alignment (registry), with the temperature, chemical potential, and distance between the walls kept constant. Changing the registry carries the film through a succession of equilibrium states, ranging from all solid at one extreme to all fluid at the other. Over a range of intermediate registries the film consists of fluid and solid portions in equilibrium, that is fluid-filled nanocapillaries separated by solid strips. The range of registries over which such fluid-solid equilibria exist depends upon the width of the grooves and the frequency of the corrugation. For grooves of width comparable to the range of the interatomic potential, fluid and solid phases cease to coexist. In the limit of very wide grooves the character of the film is similar to that of the film confined by strictly smooth walls. The rich phase behavior of the confined film due to the coupling between molecular (registry) and nano (corrugation) scales has obvious implications for boundary lubrication. © 1994 American Institute of Physics.

Curry, J. E. (2000). Structure of a model lubricant in a mica slit pore. Journal of Chemical Physics, 113(6), 2400-2406.

Abstract:

The relationship between the interlayer structure of octamethylcyclotetrasiloxane (OMCTS) lubricant and the atomic structure of confining mica surfaces is examined by Monte Carlo simulation. Results exhibited a sufficient coupling between OMCTS and mica surfaces causing a fluid lattice distortion. The coupling resulted in a nonzero shear stress which is in good agreement with experimental shear stress results.

Kim, S., Christenson, H. K., & Curry, J. E. (2002). The effect of humidity on the stability of an octadecyltriethoxysilane monolayer self-assembled on untreated and plasma-treated mica. Langmuir, 18(6), 2125-2129.

Abstract:

We investigated the stability of an octadecyltriethoxysilane (OTE) monolayer self-assembled on plasmatreated and untreated mica using a surface forces apparatus by measuring the thickness of the water layer that is adsorbed from vapor. The OTE monolayers are initially highly hydrophobic, but contact angle hysteresis indicates that water interacts favorably with the monolayers on prolonged exposure. Defects in the monolayer most likely make it possible for the water to reach the hydrophilic region between the silane headgroups and the mica. This explains why there has been very little success in measuring hydrophobic forces between OTE-coated mica surfaces. Hydrophobic forces between OTE surfaces have been successfully measured only with silica as the substrate. Even though these monolayers are not suitable for studies of the so-called hydrophobic force, they are ideal for studies designed to probe the interactions between the silane headgroups and mica. For a given relative humidity, the water film thickness is always less if the surfaces are plasma-treated before the monolayer is deposited. In the untreated case, water penetrates into the hydrophilic region between the monolayer and the mica. This does not occur in the plasma-treated case because the monolayer is more firmly anchored, most likely through covalent bonding.

Curry, J. E., & McQuarrie, D. A. (1992). On the effect of dielectric saturation on the swelling of clays. Langmuir, 8(3), 1026-1029.

Abstract:

The nonlinear Poisson-Boltzmann equation is solved with a field-dependent expression for the dielectric constant to determine the effect of dielectric saturation on swelling pressure in clays. Calculations including a scaled and an unscaled version of the approximate expression for the field-dependent dielectric constant first derived by Booth are compared. It is found that the swelling pressure decreases in all cases considered; however, the effect is significant only when the electric field at the surface is high enough to cause dielectric saturation. Nonlinear dielectric effects should be considered in models which predict surface electric fields in excess of 107 V·m-1.