Scholar Profile

Taekjip Ha

Professor
Department of Biophysics and Biophysical Chemistry
The Johns Hopkins University
725 N. Wolfe Street, WBSB 625
Baltimore, MD 21205
Fax: 410-955-0637
Email: tjha@jhu.edu
Personal Homepage
2001 Searle Scholar

Research Interests

Single-Molecule Studies of Function and Dynamics

My research program consists of two main themes: 1) Innovative technical developments of novel single molecule tools, including combination of single molecule fluorescence and biomechanical manipulations, and array-based high-throughput single molecule assays. 2) Investigation of molecular mechanisms of biomolecules such as novel DNA and RNA motifs, DNA motor proteins and membrane proteins using the techniques we develop. The fundamental understanding achieved here will have further implications for medical and bioengineering applications and may also help us design artificial machines that can approach the efficiency, specificity and robustness of natural biomolecules.

Conformational Changes of Single RNA Molecules

RNA (ribose-nucleic acids) plays important cellular roles in information storage, transfer and processing in addition to serving as a structural element for multi-protein complexes such as ribosome. It can form a variety of unique 3D structures solely determined by its sequence, hence resembles proteins. We have applied our single molecule approaches to study how an RNA molecule folds into 3D structure and dynamically changes its shape spontaneously or in response to other bio-molecules or ions. Future efforts will be focused on the conformational fluctuations of novel RNA structures with many degrees of freedom to understand the role of metal ions in governing them.

Single Molecule Study of DNA Helicases

Nucleic acids unwinding is an essential step for many biomolecular processes. For instance, DNA, containing genetic blue print for all living things, has a double helix structure formed by two strands that needs to be EunwoundD or separated before being copied. We successfully developed a unique single molecule approach that can reveal the molecular mechanism of helicases that are not accessible by other conventional methods. We will further develop our tools to investigate how helicases consume free energy released by breaking chemical bonds in the EfuelD molecule and couple it to their structural changes and propel themselves along DNA molecule and unwind it. Innovative combination of fluorescence and manipulation will be used to study how the linear and torsional tension on the DNA influence the function of helicases.

Proteins on Biological Membranes

Many important biological processes occur on membranes. Supported lipid bilayer can serve as a great model system to study protein-protein interactions and multi-protein complex organizations during myriads of biological events including vesicle fusion and cell signaling. Single molecule fluorescence techniques are well-suited for observing complex, multi-step processes of membrane proteins that are very difficult to dissect in conventional ensemble studies. We are interested in studying the mechanism of bilayer formation by vesicle fusion and developing new forms of bilayers that preserves the activity of large trans-membrane proteins. Then, we will proceed to study how membrane proteins are recruited and organized into a functional form upon external stimuli.