Current Scholars and Projects

Approximately 6.3 million fractures occur in the U.S. annually, with 5–10% resulting in nonunions, essentially the bone failing to heal after an extended period, due to impaired neovascularization, which is the formation of new blood vessels. To augment fracture healing, I designed an implantable drug delivery technology containing deferoxamine (DFO). DFO activates new blood vessel formation through iron chelation, but due to its short half-life and rapid clearance, maintaining DFO at the callus site during peak fracture angiogenesis is difficult. To overcome these limitations, I conjugated DFO to hyaluronic acid (HA), which immobilizes DFO within the fracture callus throughout the angiogenic window, making it a high-capacity iron sponge that amplifies blood vessel formation and prevents nonunions.

NMR spectroscopy confirmed that the primary amine group of DFO was covalently conjugated to the unoccupied carboxylic acid groups of the HA-DFO backbone. To observe iron binding capacity, HA (752 kDa)-DFO was incubated with the FeCl3 solution overnight. The spectra properties of the HA-DFO-Fe (III) complex were compared with that of the DFO-Fe (III) complex. The virtually identical spectra profiles in the characteristic absorption region revealed that the HA-DFO conjugate chelated to the ferric ions in a similar manner as the free DFO molecules. Spectrophotometric quantification of DFO in the HA-DFO conjugate demonstrated that 215–752 kDa conjugates retained 85–95% of the unmodified DFO’s binding capacity for Fe (III). I am currently performing optimization studies on the bioconjugates and finding ways to maximize the cross-linking profile.

These observations support the impact and potential of HA-DFO for preventing or treating delayed unions, and the advancement of this platform clinically could address a critical gap in the management of these challenging bone pathologies for patients who lack effective reconstructive options.

Chloroplasts are responsible for photosynthesis which requires a very different set of reactants than glucose-based metabolic systems. These reactions consequently need different import machineries for different reactants. The movement of substances in and out of the chloroplast needed to facilitate such reactions is understood to be accomplished by transmembrane beta barrels in the outer envelope. Yet to date, there is not a single chloroplast outer envelope protein that has been structurally solved and we remain unaware of the variety of proteins that participate in outer envelope import and export. Our laboratory has recently developed a computational algorithm to identify bacterial outer membrane beta barrels. Chloroplastic outer envelope beta barrels are likely related to bacterial beta barrels as chloroplasts most likely originated from a primitive prokaryotic cell that lived symbiotically within another cell. We are working to adapt our prokaryotic outer membrane beta barrel identifier for chloroplast. This will allow us to understand some sequence-based differences between bacterial and chloroplast outer membrane beta barrels, while also develop a database of chloroplast beta barrels that will further our understanding of chloroplast biology. So far, we have reimplemented a previous database of predicted chloroplast beta barrel sequences for all organisms in the kingdom Plantae. We have been able to describe important class-specific features of the 4,812 sequences of chloroplast outer envelope proteins we have collected so far. With this preliminary database, we have been able to test the performance of our computational algorithm against predicted chloroplast proteins, which will continue to give us insight on how to further modify our program for accurately predicting chloroplast beta barrels.

Chlamydia trachomatis has a characteristic biphasic developmental cycle. The signals and mechanisms that regulate it are still poorly understood. One of the signaling pathways that is believed to govern this cycle is the Rsb (Regulator of Sigma B) system. This pathway allows the cell to sense and respond to stress and starvation. This, in turn, prompts the organism to grow and develop. Because of its role in C. trachomatis' development, one of our lab's focuses is to understand this pathway's mechanisms.

In this system, several proteins interact with each other based on the phosphorylation state of an intermediate: RsbV1. This project seeks to determine the importance of RsbV1's phosphorylation state. To do so, I study a mutant form for RsbV1 called RsbV1S56A. RsbV1S56A's main feature is that it cannot be rephosphorylated during development, unlike the WT form. One of the methods used is to compare the growth of WT and mutant strains of C. trachomatis. I also examine the impact of the mutation in the organism's morphology. We expect that seeing the role of RsbV1's phosphorylation will help us better understand how the Rsb system affects C. trachomatis' development. C. trachomatis is the most prevalent sexually transmitted bacterial infection worldwide. Thus, understanding its development can help us determine better ways to combat infection.