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biochemistry and biophysics


Associate Professor of Biochemistry and Biophysics

913A Stellar-Chance Labs
T: (215) 898-5039 (office)
T: (215) 898-4476 (lab)
F: (215) 573-7058

B.A. Carleton College (1997) Biology
Ph.D. University of Virginia (2002) Biochemistry and Molecular Genetics



Dr. Black's laboratory is interested in how particular proteins direct accurate chromosome segregation at mitosis. In humans, the chromosomal element—the centromere—that directs this process is not defined by a particular DNA sequence. Rather, the location of the centromere is dictated by an epigenetic mark generated by one or more resident proteins. These centromeric proteins interact directly with the DNA to create a specialized chromatin compartment that is distinct from any other part of the chromosome. By taking biophysical, biochemical, and cell biological approaches, our work is to define the composition and physical characteristics of the protein and protein/DNA complexes that epigenetically mark the location of the centromere on the chromosome. This work involves building centromeric chromatin from its component parts for analysis of its physical characteristics, developing biochemical assays to reconstitute steps in the process of establishing and maintaining the epigenetic mark, and using cell-based approaches to study the behavior of proteins involved in centromere inheritance and function.

For the physical studies of centromeric chromatin, one emerging technique that has already proven extremely useful is hydrogen/deuterium exchange coupled with mass spectrometry to assess conformational flexibility of centromeric proteins. Hydrogen/ deuterium exchange along the polypeptide backbone occurs at rates that can span a huge dynamic range, and this experimental approach has been applied by many laboratories to diverse problems in protein chemistry [including several ongoing efforts at UPenn]. These include global questions of protein folding, as well as more protein-specific questions of conformational alterations upon assembly into higher-order structures or upon changing states in the case of "molecular switches". We are interested in extending this technique to assess the properties conferred by the incorporation of centromeric proteins into higher-order chromatin structure, as well as to the study of proteins involved in other steps of regulating chromosome segregation.

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