After receiving her Ph.D., Professor Pollack came to Cornell to work with the Low Temperature Physics group as a Postdoctoral Associate (1989-1991) and as a Research Associate (1991-1997) in the Microkelvin Laboratory. In 1997, with support from the NSF and the LASSP Biophysics Group, she changed the focus of her research program to Biophysics. In 1999 she became Senior Research Associate in LASSP. She joined the faculty in Applied and Engineering Physics in 2000. She is affiliated with the Nanobiotechnology Center and with CHESS (G-line).  

Research Interests 

My group is studying both self-assembly/folding of macromolecules and conformational changes associated with biological function.  We develop and use new tools to trigger and monitor shape changes to access novel information about these processes. 

Conformational changes can be triggered by modifying the solvent around a macromolecule.  For example, protein folding can occur in response to a change in pH or to the dilution of a chemical denaturant.  Many conformational changes occur rapidly, orders of magnitude faster than the characteristic millisecond mixing times associated with commercial fluid mixers.  Using micro/nanofabrication techniques, we produce flow cells with mixing times of microseconds.  Flexibility of design makes it possible to use these rapid mixers in conjunction with different probes of macromolecular structure, including x-ray scattering and fluorescence. 

One of our major initiatives is the use of synchrotron small angle x-ray scattering to measure the time dependence of the size and shape of macromolecules (proteins and nucleic acids) as they fold.  A key, unresolved question in protein folding is: what is the role of collapse of the denatured polypeptide chain?  Collapse is an important step in the conversion of an expanded, denatured amino acid chain into a compact, biologically active protein.  These experiments allow us to monitor both the time required for collapse as well as the size of the compact denatured or intermediate states.  Prior to our initial experiments, this information was not accessible to experimentalists on the sub-millisecond time scale! 

With this new technique, it is now possible to characterize transient states that occur during the folding process.  Information of this type is critical for comparison of experiment to untested theories of the initial events in macromolecular folding.  

Selected Publications 

• X. Qiu, K. Andresen, J.S. Lamb, L.W. Kwok and L. Pollack, “Abrupt transition from free, repulsive to condensed, attractive DNA phase, induced by multivalent polyamine cations”, Phys. Rev. Lett. 101, 228101 (2008). 
•  J.S. Lamb, B. Zoltowski, S. A. Pabit, B. R. Crane and L. Pollack, “Time-resolved dimerization of a PAS-LOV protein measured with photocoupled small angle x-ray scattering”, J. Amer. Chem. Soc. 130, 12226 (2008).
• L. Li, S.A. Pabit, J.S. Lamb, H.Y. Park and L. Pollack, “Closing the lid on DNA end-to-end stacking interactions”, Appl. Phys. Lett. 92, 223901 (2008).
• L. Li, S.A. Pabit, J.S. Lamb, H.Y. Park and L. Pollack, “Closing the lid on DNA end-to-end stacking interactions”, Appl. Phys. Lett. 92, 223901 (2008). J.S. Lamb, L. Kwok, X. Qiu, K. Andresen, H. Park and L. Pollack, “Reconstructing three dimensional shape envelopes from time resolved small angle x-ray scattering data”,  J. App. Cryst. 41, 1046 (2008).
• J. Schlatterer, L.W. Kwok, J.S. Lamb, H.Y. Park, K. Andresen, M. Brenowitz and L. Pollack, “Hinge stiffness is a barrier to RNA folding”, J. Mol. Biol.379, 859 (2008).
• K. Andresen, X. Qiu, S. A. Pabit, J. S. Lamb, H.Y. Park, L.W. Kwok and L. Pollack, “Mono and tri-valent ions around DNA: a small angle scattering study of competition and interactions”, Biophys. J.,  95, 287 (2008).
• H.Y. Park, S.A. Kim, J. Korlach, E.Rhoades, L.W. Kwok, W.R. Zipfel, M.N. Waxham, W.W.Webb and L. Pollack, “Conformational changes of calmodulin upon  Ca²⁺ binding studied with a microfluidic mixer”, Proc. Natl Acad Sci USA, 105(2), 542 (2008).   
• X. Qiu, K. Andresen, L.W. Kwok, J.S.  Lamb, H.Y. Park, and L. Pollack,  “Inter-DNA attraction mediated by divalent counterions” Phys. Rev. Lett., 99 038104 (2007).
• H.Y. Park, X. Qiu, E. Rhoades, J. Korlach, L.W. Kwok, W.R. Zipfel, W.W. Webb and L. Pollack, “Achieving uniform mixing in a microfluidic device: hydrodynamic focusing prior to mixing” Anal. Chem., 78, 4465 (2006).
• X. Qiu, L.W. Kwok, H.Y. Park, J.S.  Lamb, K. Andresen, and L. Pollack,  “Measuring inter-DNA potentials in solution” Phys. Rev. Lett., 96 138101 (2006).
• L.W. Kwok, I. Shcherbakova, J.S. Lamb, H.Y. Park, K. Andresen, H. Smith, M. Brenowitz and L. Pollack,  “Concordant measurements of folding kinetics from local and global perspective” J. Mol. Biol., 355, 282 (2006)