My general research goal is to engineer molecular probes and to develop new photonic techniques to enable biological discovery. To this end, we integrate a variety of approaches including molecular design and engineering, imaging, chemical synthesis, molecular and cellular biology.
Our current research focuses on two areas: (1) Develop photonic probes for biological applications. (2) Study functions of gap junction coupling in C elegans.
(1) Develop photonic probes for biological applications.
Caged compounds allow researchers to investigate molecular and cellular dynamics with pinpoint accuracy. We are exploring new concepts and new caging chemistry to develop caged probes for biological applications.
Photo-activatable fluorophores (caged dyes) are powerful imaging probes for tracking spatiotemporal dynamics of molecular and cellular movements in biological systems. They have been widely used in tracking the migration trajectory of proteins or oligonucleotides in cells, in following cell lineage in development, in monitoring cell-cell coupling through gap junction channels, and, recently, in high resolution imaging down to nanometer scale by using photo-activation localization microscopy. We are developing new caged dyes that are soluble and biocompatible, possess friendly chemistry for bioconjugation, and exhibit robust contrast enhancement upon photolysis. For single molecule imaging, we choose fluorophores that are bright, photo-stable, and available in different colors.
A related project is to develop new caging chemistry suitable for two photon photolysis. The high spatial selectivity of two photon uncaging is ideally suitable for resolving cell signaling in three dimensions. In addition to caged receptor ligands and signaling molecules, we also plan to apply new caging chemistry to develop photo-activatable indicators. Such indicators would enable analyzing biochemical activities cell by cell in tissues, so we can dissect the organization, interaction, and hierarchy of functional network, for instance, in mapping neural circuitry of central nervous systems.
Magnetic Resonance Imaging (MRI) is a truly non-invasive imaging technique that provides 3-D images of internal structures of living organisms. Recent advances in MRI instrumentation and pulse sequence design have greatly improved the spatial and temporal resolution. At high fields (3T to 11.7T), it is now possible to acquire images with spatial resolution near cellular levels. We are developing new MR imaging techniques and contrast agents to follow cell function in living organisms.
(2) Functions of gap junction coupling in C elegans.
Intercellular communication through gap junction channels is wide spread in multicellular organisms and is essential for many vital physiological processes. We are interested in understanding the functions of gap junction coupling during development, using the nematode C elegans as a model because it has a very limited number of cells, invariant cell lineage and favorable optical properties for imaging.
We take two complementary approaches to address the question, First, we are developing new probes and imaging techniques to map the coupling pattern and dynamics during development, and to define the molecular signals that diffuse through gap junction channels. Both caged fluorophores and voltage sensitive dyes with improved sensitivity and fast response kinetics will be developed and applied.
The second approach is to develop specific pharmacological reagents to modulate junctional communication. Ideally, these reagents should be selective against a unique class of gap junction proteins, be activatable at the time and location of our choice, and can be applied to model organisms non-invasively. Once being developed, these reagents will also have important applications in studying the roles of electrical synapses in forming neural circuitry, and in modulating behavior.
RESEARCH INTERESTS
Intercellular communications through gap junctions
Molecular engineering of fluorescent sensors for cellular imaging
Wide field, confocal and multi-photon fluorescence microscopy
Mechanisms and functions of cellular calcium signaling
RECENT PUBLICATIONS
Genghua Zheng, Yan-Ming Guo & Wen-hong Li, "Photoactivatable and Water Soluble FRET Dyes with High Uncaging Cross Section" J. Am. Chem. Soc., 129:10616-10617, 2007
Kenneth Dakin & Wen-hong Li, "Infrared LAMP, Two-Photon Uncaging and Imaging of Gap Junctional Communication in Three Dimensions" Nature Methods, 3:959, 2006
Kenneth Dakin & Wen-hong Li, "Local Ca2+ Rise Near Store Operated Ca2+ Channels Inhibits Cell Coupling During Capacitative Ca2+ Influx" Cell Commun. Adhes., 13:29-39, 2006
Ying Jie Wang, Wen-hong Li, Jing Wang, Ke Xu, Ping Dong, Xiang Luo & Helen L. Yin, "Critical Role of PIP5KI?87 in InsP3-mediated Ca2+ Signaling" J. Cell Biol., 167:1005-1010, 2004
SIGNIFICANT PUBLICATIONS
Quan Zheng, Houquan Dai, Matthew E. Merritt, Craig Malloy, CaiYuan Pan & Wen-hong Li, "A New Class of Macrocyclic Lanthanide Complexes for Cell Labeling and Magnetic Resonance Imaging Applications" J . Am. Chem. Soc., 127:16178-16188, 2005
Kenneth Dakin, YuRui Zhao & Wen-hong Li, "LAMP, A New Imaging Assay of Gap Junctional Communication Unveils That Ca2+ Influx Inhibits Cell Coupling" Nature Methods, 2:55-62 (News & Views, 12-14), 2005
YuRui Zhao, Quan Zheng, Kenneth Dakin, Ke Xu, Manuel L. Martinez & Wen-hong Li, "New caged coumarin fluorophores with extraordinary uncaging cross sections suitable for biological imaging applications" J . Am. Chem. Soc., 126:4653-4663, 2004
Yan-Ming Guo, Shiuhwei Chen, Premnath Shetty, Genhua Zheng, Rueyling Lin, Wen-hong Li, "Imaging dynamic cell-cell junctional coupling in vivo using Trojan-LAMP" Nature Methods, 5:835-841, 2008
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