Current Research
Mechanism of Transcription
Transcription is an important process in gene expression. During transcription, RNA polymerase translocates along a DNA template while copying genetic information from DNA to RNA. We study the mechanism by which RNA polymerase moves by tracking the motions of individual RNA polymerase molecules and by theoretically modeling the polymerase kinetics.
Cornell Chronicle Article
Unpacking DNA
Nucleosomes are the fundamental packing units of the DNA in chromosomes. The stability of nucleosomes regulates the accessibility of DNA to many DNA-binding proteins that carry out a variety of cellular functions. We study nucleosomal stability by mechanically unpacking the nucleosomes.
PNAS Commentary
Cornell News Article
Helicase Unwinding of DNA
Helicases are enzymes essential for DNA replication, recombination and repair. In these biological processes helicases serve the function of separating (unwinding) the two strands that form the DNA double helix. Helicase unwinds DNA by translocating along one strand, while simultaneously separating the second strand. Using optical tweezers we study the properties of translocation and probe the mechanism of strand separation.
Cell Commentary
Cornell Chronicle Article
Cornell Daily Sun Article
Tompkins Weekly Article
Development of Novel Techniques
Unzipping
Protein-DNA interactions underlie many cellular activities. Our lab develops new physical / biophysical techniques to directly probe these interactions. Our Unzipping Force Analysis of Protein Association (UFAPA) is a novel and versatile method for detection of the position and dynamic nature of protein-DNA interactions. For some interesting applications of this technique, please see our work on restriction enzymes and DNA repair enzymes.
Cornell News Article
Cornell Chronicle Article
Twisting
Our lab also pioneered an angular trapping technique for simultaneous torque and force generation and detection. When a birefringent particle is trapped in a polarized laser beam, rotation of the laser polarization induces rotation of the particle while torque exerted on the particle is detected as a change in the polarization of the trapping beam. This technique allows the control and detection of the torque of a biological molecule attached to the particle and has opened new dimensions for applications of optical trapping techniques.
Physical Review Focus
We have also developed specialized particles for optical rotation experiments, making use of the world-class nanofabrication facilities located at Cornell's Ithaca campus. Highly homogenous quartz nano-cylinders have been produced in mass quantities, with specific biological functionalization for use in DNA torsional experiments.
