e-mail: keshet1@umbc.edu
PhD Chemical Engineering (2010), UMBC
B.S Physics (2004) The Hebrew University of Jerusalem
PhD advisor: Theresa Good
Chemical & Biochemical Engineering
University of Maryland Baltimore County (UMBC)
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Ben Keshet e-mail: keshet1@umbc.edu PhD Chemical Engineering (2010), UMBC B.S Physics (2004) The Hebrew University of Jerusalem PhD advisor: Theresa Good Chemical & Biochemical Engineering University of Maryland Baltimore County (UMBC) |
| Research I work in Theresa Good's lab, where we study the aggregation and toxicity of β amyloid protein (Aβ) in Alzheimer's disease. In my research I use a combination of biophysical and computational tools along with tissue culture experiments to understand the structure - activity relationship of Aβ. Specifically, I try to (1) elucidate molecular level differences between different aggregation species, and (2) identify amino acids that are essential for Aβ toxicity. I have used the following tools:
The N-terminus of Aβ Although the N-terminus of Aβ is usually considered as unstructured and solvent accessible, we identified some differences in solvent accessibility between the toxic Aβ oligomer and less toxic fibril within the N-terminus segment. Additionally, we found differences in solvent accessibility between Aβ fibrils of two morphologies. The species with higher exposure at Arg5 of Aβ are more toxic to cells in-vitro. An alternative explanation - can size and concentration explain some of the differences in toxicity between Aβ fibril and intermediate? Despite some molecular level differences we and others have identified between Aβ oligomers and fibrils, substantial evidence suggest molecular level similarities between the Aβ oligomer and fibril. This result may imply that the intermediate appears more toxic than the fibril due to its higher mobility and higher concentration, and not due to differences in structure specific interactions of the different aggregated species. We developed a simplified model, which can explain the differences in biological activity between the toxic intermediate and the mature fibrils, using a diffusion-limited reaction model and geometry considerations (Biotechnol. Bioeng. 2010 106(2), 333-7) Toxicity inhibitors as probes for loci on Aβ important for toxicity We elucidated the binding sites of small molecular weight toxicity inhibitors, as a means to explore residues and surfaces on Aβ that are associated with toxicity. Our overall goal is to identify molecular level details of the interaction of Aβ with neurons. We hypothesized that some of the inhibitors share the same binding sites, and that the common binding loci are significant for toxicity. Computational docking was employed to predict the binding of several small molecular weight inhibitors to the Aβ fibril. We tested the predications experimentally using single residue Aβ mutants, or Aβ chemically modified at specific amino acids. Computational docking predicted two common binding sites for all the inhibitors. Experimentally, we found that at least two inhibitors; Congo red and myricetin, which are structurally dissimilar, share the same two binding sites on Aβ. Three additional inhibitors; curcumin, nicotine and melatonin, seem to interact with Aβ at at one the same sites. Our finding may suggest that the common sites are important for the Aβ interaction with cells (Protein Sci. 2010 19(12) 2291-2304). We are currently investigating whether the binding sites of the toxicity inhibitors have a role in Aβ toxicity. We also initiated a virtual screening of large databases using docking in a search for novel inhibitors that can bind at the identified sites. Dissertation: Towards understanding the molecualr details of beta-Amyloid neurotoxicity in Alzheimer's disease, 2010 Additional Publications: Biochim Biophys acta, 2009, 1788(9) 1714-21 |