Ava Yun Lin

Email: linxx318@umn.edu

Year Entered: 2006

Degrees Received:
B.S. Molecular Biology and Biochemistry, University of California-Irvine, 2006

Thesis Advisor: David Thomas, Ph.D., Biochemistry, Molecular Biology, and Biophysics Graduate Program

Past Research Experience

My focus is on the molecular changes of the cleft during the crosslinking and contraction cycle in relation to actin or nucleotide binding. Several crystal structures have been proposed for the pre-hydrolysis myosin II, pre-power stroke myosin II and the rigor state of myosin V. We intend to compare these proposed structures with DEER EPR and CW-EPR spectrometry and molecular dynamics simulation (MD simulation) to evaluate and resolve the proposed structural states under non crystalline conditions. Previous experiments in the lab have shown that there are a mixture of at least two distinct structural states present in each of the pre-hydrolysis, post-hydrolysis and rigor states of the myosin-actin cross bridge, indicative of a more ordered to disordered transition as opposed to the open and close mechanism previously determined. My project will involve trying to elucidate how each of the structural states correlate with the biochemical conditions (ADP vs. ATP binding, hydrolysis, etc.).

To examine the opening and closing of the myosin cleft, we engineer cysteine spin-labeling sites in a Dicty myosin II model depleted of other reactive cysteine molecules. Paramagnetic spin labels (IPSL, MTSSL) are attached to each cysteine molecules in order to visualize the conformational changes between the upper and lower 50 kDa domains of the myosin head. Some approaches we plan to use include crosslinking the upper and lower 50kDa domains to determine the correlation between cleft distance and the strength of actin binding. Distance measurements of the cleft will also include DEER CW-EPR and possible biofunctional EPR studies in the evaluation.