Prior Projects
Dendrimer-DNA Complexes: Structure and Forces
Cationic dendrimers have shown potential as gene delivery vectors due to their ability to condense DNA and protect from cellular and restriction nuclease. Due to their potential as gene delivery agents, characterization of packaging and forces within cationic dendrimer-DNA complexes, or dendriplexes is needed. We use osmotic stress coupled with x-ray scattering to study fundamental molecular scale interactions and supramolecular self-assembly of low generation poly(amido amine) (PAMAM) dendrimer-DNA complexes. Dendrimer-DNA assembly displays fundamentally different physical behavior than condensation by linear cation. These studies begin to elucidate the role of cation topography in DNA condensation.
Small molecule drug interactions with DNA
Many small molecules (such as drugs, ligands, etc.) are able to recognize and bind to single-or double-stranded nucleic acids, often inducing structural alterations. The unique double helix structures of DNA allows for binding through various modes including covalent binding (DNA-adducts), major or minor groove binding, and intercalation. Currently, little is known about small molecule drug interactions with highly packaged DNA that is typically found within cells. The reactivity of drugs and mutagens toward packaged DNA is presumably quite different from dilute DNA, and dependent on both accessibility and changes in DNA-DNA interaction energies. We are working on measuring directly the forces induced by these DNA drug interactions on DNA molecules in various states of condensation and correlating these forces to DNA packaging, DNA damage and disease.
Intracellular Gene Delivery: Understanding rate-limiting steps to efficient transfection
Endocytosis is the cellular process by which molecules, such as proteins, are absorbed from outside the cell membrane by engulfing within a membrane-bound vesicle. Once compartmentalized, these endosomes are either recycled back to the surface or are sorted for degradation through acidification. Since most non-viral carriers of DNA depend on endocytosis for their import into cells; endosomal release and the subsequent DNA release therefore corresponds to two of the most important barriers to efficient transfection. We are actively involved in using physical techniques including SAXS and FCS to better understand these mechanisms and ultimately engineer better optimized gene delivery systems.
Self-assembly of proteins with engineered nanomaterials
Due to their high free energy, ENM surfaces in contact with biological media are rapidly covered by biomacromolecules that form a corona. In blood the coating is proteins, in lung it might be surfactants, and in the environment it might be natural organic matter. In blood, the corona typically consists of a near monolayer initially composed of the more abundant proteins (creating a “soft corona”). Over time proteins that have a higher affinity for the ENM predominate, to form a more stable, or “hard corona”. ENM interactions with their local environments are dynamic and rapid; their time course is poorly understood. The nature of ENM surfaces dictates the make-up and formation of the protein corona that ultimately dictates the ENM fate and effects in vivo.
Due to their high free energy, ENM surfaces in contact with biological media are rapidly covered by biomacromolecules that form a corona. In blood the coating is proteins, in lung it might be surfactants, and in the environment it might be natural organic matter. In blood, the corona typically consists of a near monolayer initially composed of the more abundant proteins (creating a “soft corona”). Over time proteins that have a higher affinity for the ENM predominate, to form a more stable, or “hard corona”. ENM interactions with their local environments are dynamic and rapid; their time course is poorly understood. The nature of ENM surfaces dictates the make-up and formation of the protein corona that ultimately dictates the ENM fate and effects in vivo.
In order to understand the mechanism of Aβ assembly and dissociation in more detail, we use fluorescence correlation spectroscopy (FCS) to study diffusion of Aβ species at near physiological concentrations in the presence and absence of modulators of Aβ assembly.