Sharonda LeBlanc, Ph.D.
UNC Chapel Hill
Postdoctoral Research Associate, Department of Chemistry
will be presenting
“Using single-molecule fluorescence to study nanomaterials and protein-DNA interactions”
Single molecule methods enable the investigation of rare and/or transient molecular events. I will introduce single
molecule fluorescence experimentation using an example from my graduate work where I studied the optical
properties of single quantum dots under the influence of proximal electric fields. The remainder of the talk will
focus on my current project investigating the coordinated action of enzymes that repair mismatched DNA using
single molecule fluorescence resonance energy transfer (smFRET).
DNA mismatch repair (MMR) is a post-replicative pathway that corrects rare mistakes in the genome of all
organisms. MMR is initiated by MutS and MutL homologs which contain DNA binding and ATPase activity. Single
amino acid mutations in MutS and MutL proteins have been linked to hereditary and sporadic colorectal cancer,
the third most common cancer worldwide. We use in vitro smFRET to investigate the molecular mechanism of
MMR, which involves coordinated transient interactions between approximately eight different enzymes. Site-
specific fluorescence labeling strategies enable us to monitor the conformational dynamics of proteins and DNA
during these interactions. We have identified a sequential pathway of conformational changes in MutS and DNA
that is likely necessary to signal for downstream repair with the rest of the MMR machinery. Understanding the
dynamic interactions between MutS, MutL, and DNA represents a key step toward pinpointing failures in mutants
and elucidating molecular mechanisms of cancer development.
Dr. Sharonda Johnson LeBlanc is currently a postdoctoral scholar in the Chemistry Department at UNC-Chapel
Hill working with Prof. Dorothy Erie and Prof. Keith Weninger (NC State). Her research projects, funded by an
NIH K01 Career Development Award from the National Cancer Institute focuses on using single-molecule
techniques to study dynamic protein-DNA interactions involved in DNA repair pathways. She graduated from the
Nanoscale Science Ph.D. program at UNC Charlotte in 2012.