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Mathematics and Natural Sciences

Brian Dyer
Fluorescence Lifetime Imaging to elucidate protein membrane interactions in living cells

Fluorescence microscopy is transforming the way we study molecular processes in living cells, because it is an incredibly sensitive method that allows real-time visualization of specific components in the cell in response to various stimuli. The Dyer lab uses fluorescence microscopy to image how a virus invades a healthy cell in the process of infection. The first critical step in viral infection is membrane fusion, a molecular process that joins the viral membrane with the protective outer membrane of the host cell, allowing the virus to inject its contents into the host and thus infect it. A better understanding of this process would help to develop more effective drug therapies to prevent viral infection. A major difficulty in studying the viral invasion mechanism using fluorescence imaging is autofluorescence of cells that produces an interfering background glow, degrading the image quality. We have recently acquired a fluorescence lifetime imaging microscope that is capable of minimizing the autofluorescence background in live cell imaging. This proposal seeks funding for a new laser to be integrated into the microscope system, to provide greater sensitivity and accessible laser wavelengths. The proposed enhanced FLIM system is one of a kind, in the region and probably in the country, so it will represent a unique new capability for the Emory research community.

Stefan Lutz
Engineering nanocompartments for multi-dimensional self-assembly

The application of enzymes as biocatalysts for chemical reactions holds great promise for greener and more sustainable production of high-value products such pharmaceutical intermediates. To increase the lifetime and improve productivity of these biocatalysts, our proposal wants to explore the use of nano-size spherical particles called nano-compartments. Themselves made up of protein, these nano-compartments form spherical assemblies which allows for encapsulation of biocatalysts. Potential benefits of encapsulation that will be studied as part of this application includes increased enzyme stability which should translate into prolonged biocatalyst lifetime (specific aim 1). At the same time, we will try to exploit the protein-based nature of the nano-compartments by introducing small protein docking sites, enabling the assembly of multiple nano-compartments into orderly two and three-dimensional macromolecular structures (specific aim 2). We hypothesize that such assemblies create high-density catalyst system, which results in further catalytic enhancements. In addition, the system enables orderly packaging of two or more biocatalysts to facilitate multiple consecutive reaction steps.

Connie Roth
Developing Optical Dye Technique for Polymer Modulus Measurements

Polymers are used extensively as light-weight, structurally supportive layers, where their performance in such applications are predominantly determined by their modulus (stress-strain response). Modulus changes by three orders of magnitude on cooling through the glass transition temperature (Tg) going from a rubbery liquid to a glassy solid. Studies have shown that large property changes occur when the sample size is reduced to hundreds of nanometers. Local measures of Tg and relaxation times have found that deviations in the average material properties of thin films are associated with a gradient in local dynamics with depth emanating from the perturbing boundaries of the sample. Although never previously measure, there is strong reason to believe that the local modulus also varies significantly near these boundaries and interfaces. The proposed research aims to develop a unique optical method for measuring the local modulus as a function of depth near such boundaries. Azo dyes undergo conformational changes when exposed to specific wavelengths of light. When embedded in a polymer, these switching dyes created local strain (deformation) in the polymer. This will cause a locally propagating wave that depends on the local modulus. We will use a pyrene dye whose fluorescence response is highly sensitive to local density to measure the polymer material’s response to the local azo switching. The URC fund will be used to demonstrate that the resulting pyrene fluorescence response is correlated with local modulus by calibrating the pyrene fluorescence signal with time and temperature dependent modulus data collected on equivalent polymer films using a micro tensile tester.

Lars Ruthotto
Mathematics and Computer Science
Numerical Methods for Quantitative MRI

Magnetic Resonance Imaging (MRI) has been used successfully to obtain in-vivo information about an object. For example, it is commonly used in the neuroscience to obtain anatomical and functional information about the human brain, which is important for understanding and diagnosing certain diseases or planning surgeries.

However, coupled with state-of-the-art numerical and statistical methods, MRI can provide much more than just images of the patient. The main goal of quantitative MRI is to obtain standardized information about the tissue micro-structure. By estimating parameters of physical models from MRI data, new, not directly observable biomarkers, can be obtained that help to better understand how the brain works.

The success of qMRI relies on further research from various disciplines. This project develops new mathematical insight and efficient computational tools to improve the accuracy and robustness of parameter estimation. To this end, state-of-the-art tools from numerical optimization, numerical linear algebra, parallel processing and partial differential equations are employed.

Gonzalo Vazquez-Prokopec
Environmental Science
Urban Ecology of West Nile Virus in Atlanta, GA

West Nile virus (WNv) is a globally distributed urban vector-borne pathogen transmitted by Culex mosquitoes among song birds. WNv was first introduced into the continental U.S. in 1999 and rapidly spread throughout all States causing 41,762 infections and 1,765 deaths between 1999-2014. Previous urban eco-epidemiological research of WNv in the Southeastern U.S. has focused on the causes of human infection, identifying the invasive species Culex quinquefasciatus as culprit for virus spillover into humans. Other native mosquitoes (e.g., Culex restuans, Culex nigripalpus), however, are capable of transmitting WNv to birds and their role in the persistence of the virus during and after winter months is unknown. Evidence from our ongoing research showed that Cx. restuans can be infected earlier in the spring, 1-2 months before the detection of infected Cx. quinquefasciatus. Those findings prompted me to hypothesize that the seasonal winter persistence and spring reemergence of WNv is linked to the complex ecological dynamics between an enzootic vector (Cx. restuans) and an amplifying vector (Cx. quinquefasciatus). To test this hypothesis, I will utilize experimental field perturbations of Cx. restuans and Cx. quineufasciatus in four urban parks of Atlanta, GA, and monitor the impact of suppressing one species on the temporal pattern of virus infection in mosquitoes and birds. This project will innovatively explore the complex role that the community of vectors can have on pathogen establishment and persistence and pave the road for the development of a theoretical and empirical framework for targeted control strategies in complex multi-vector multi-host disease systems.