The overall objective of research in my laboratory is to study the dynamics of cellular processes as they occur in real time at the single molecule and single cell level. The depth and breadth of the research require an interdisciplinary approach, combining biological, biochemical and biophysical methods to quantitatively address compelling biological problems. With unprecedented sensitivities to detect individual molecules, the use of single molecule and single cell approaches allows one to access information that is not readily available to traditional ensemble measurements. For example, one can explore heterogeneities among the different molecules and cells within a population and, more importantly, track motions of individual molecules and their biochemical interactions. These are particularly suitable for illustrating the mechanisms of many cellular processes resulting from highly dynamic interactions among proteins, DNAs and small molecules, which are not usually present in large copy numbers inside the cells. For instance, gene regulation, cell signaling and large intracellular complexes assembly are just a few areas that we are currently studying. We are also interested in developing better probes, such as fluorescent reporters and single pair fluorescent resonance energy transfer (spFRET) reporters, to track fast kinetics of cellular processes and interactions among protein complexes. The use of single molecule fluorescence microscopy methods, in combination with statistical analysis will not only complement traditional population studies, but also shed new lights on the mechanisms of these cellular processes at an unprecedented level. The methodology developed in the research will open a new dimension in characterizing biological systems in live cells.

Publications:

Xiao J ., Elf, J., Li, G., Yu, J., Xie X. S., Imaging gene expression in living cells at the single molecule level. Single Molecules: A Laboratory Manual, edited by Selvin P., and Ta H. 2007, Cold Spring Harbor Laboratory Press, Cold Spring Harbor, NY. (in press)

Singleton SF., Roca AI., Lee AM., Xiao J., Probing the structure of RecA-DNA filaments. Advantages of a fluorescent guanine analog. Tetrahedron, 2007, 63(17):3553-3566

Yu J., Xiao J., (equal contribution), Ren X., Lao K., Xie X.S., Probing gene expression in live E. coli cells: one molecule at a time. Science, 2006, 311(5767):1600-3

Xiao J., Lee, A., Singleton SF. Direct evaluation of a kinetic model for RecA-mediated DNA-strand exchange: the importance of nucleic acid dynamics and entropy during homologous genetic recombination. Chembiochem. 2006, 7(8):1265-78

Xiao J., Lee, A., Singleton SF. Construction and evaluation of a kinetic scheme of RecA mediated DNA strand exchange. Biopolymers. 2006, 81(6):473-96

Lee A., Xiao J.,Singleton SF. Origins of sequence selectivity in homologous genetic recombination: insights from rapid kinetic probing of RecA-mediated DNA strand exchange. J Mol Biol. 2006, 360(2):343-59

Xiao J., Singleton SF., Elucidating a key intermediate in homologous DNA strand exchange: structural characterization of the RecA∙triple-stranded DNA complex using fluorescence resonance energy transfer. J. Mol. Biol, 2002 Jul 12;320(3):529-58

Singleton SF., Xiao J., The Stretched DNA geometry of recombination and repair nucleoprotein filaments. Biopolymers, 2001-2002;61(3):145-58

Martin SR, Lu AQ, Xiao J, Kleinjung J, Beckingham K, Bayley PM., Conformational and metal-binding properties of androcam, a testis-specific calmodulin-related protein from Drosophila. Protein Science, 1999, Nov 8(11):2444-54.