News

News

Research Highlights

Luo et al. published "Dynamic Distance Disorder in Proteins Is Caused by Trapping" in J. Phys. Chem. B [110 , 9363-9367 (2006)] .
Ganikhanov et al. published a new approach for CARS microscopy. Please see "High-sensitivity vibrational imaging with frequency modulation coherent anti-Stokes Raman scattering (FM CARS) microscopy" in Optics Lett. [31, 1872-1874 (2006)].
Légaré and Evans et al. published a proof-of-principle demonstration of CARS endoscopy. See "Towards CARS Endoscopy" in Opt. Express [14 , 4427-4432 (2006)].
An ideal laser source has been developed for CARS imaging. See Ganikhanov et al "Broadly tunable dual-wavelength light source for coherent anti-Stokes Raman scattering microscopy" in Optics Lett. [31, 1292-1294 (2006)].
An invited perspective article, "Living Cells as Test Tubes", by Xie, Yu, and Yang appeared in Science [312, 228-230 (2006)].
Blainey et al. published an article in Proc. Natl. Aca. Sci. [103, 5752-5757 (2006)] entitled A base-excision DNA-repair protein finds intrahelical lesion bases by fast sliding in contact with DNA.
The Xie group reported on its four year venture in probing gene expression in live cells on a single-molecule basis with simultaneous papers in Nature [440, 358-362 (2006)] by Cai, Nir and Xie entitled Stochastic protein expression in individual cells at the single molecule level, and Science [311, 1600-1603 (2006)] by Yu, Xiao et al. entitled Probing Gene Expression in Live Cells, One Protein Molecule at a Time.
Culminating our effort on single molecule enzymology, Brian English et. al. published a paper in Nat. Chem. Bio. [published online (2006)] entitled Ever-fluctuating single enzyme molecules: Michaelis-Menten equation revisited.
Xiaolin Nan et al published a paper reporting direct visualization of nanometric stepping of molecular motors in a living cell in J. Phys. Chem. [109, 24220-24224 (2005)] entitled Observation of Individual Microtubule Motor Steps in Living Cells with Endocytosed Quantum Dots.
Wei Min et al. published a paper in Nano Letters entitled Nonequilibrium Steady State of a Nanometric Biochemical System: Determining the Thermodynamic Driving Force from Single Enzyme Turnover Time Traces Nano Lett. [5, 2373-2378 (2005)].
Wei Min et al. published a comprehensive review article of our group's work in single-molecule enzymology in Accounts of Chemical Research entitled Fluctuating Enzymes: Lessons from Single-Molecule Studies Acc. Chem. Res. [36 , 923-931 (2005)].
Conor L. Evans et al. published a paper in the Proceedings of the National Academy of Sciences entitled Chemical Imaging of Tissue in vivo with Video-rate Coherent Anti-Stokes Raman Scattering Microscopy Proc. Natl. Aca. Sci. [102 , 16807 (2005)]. This work is a collaboration with Charles Lin's group at MGH.
Dr. Sam Kou et al. published a feature paper in the Journal of Physical Chemistry B entitled Single-Molecule Michaelis-Menten Equations Phys. Chem. B [109, 190-19081 (2005)].
Wei Min et al. published a paper in the Physical Review Letter entitled Observation of a Power-Law Memory Kernel for Fluctuations within a Single Protein Molecule Phys. Rev. Lett. [94 , 198302 (2005)].
Eric O. Potma et al. published a paper in the January issue of ChemPhysChem entitled Direct Visualization of Lipid Phase Segregation in Single Lipid Bilayers with Coherent Anti-Stokes Raman Scattering Microscopy ChemPhysChem [6 , 77 (2005)].
Conor L. Evans et al. published a paper in the December issue of Optics Letters entitled Coherent anti-Stokes Raman scattering interferometry: determination of the real and imaginary components of nonlinear susceptibility χ ⁽³⁾ for vibrational microscopy Optics Lett. [29, 2923 ( 2004)].
Dr. Sam Kou and Professor Sunney Xie published a paper in the Physical Review Letter entitled Generalized Langevin Equation with Fractional Gaussian Noise: Subdiffusion within a Single Protein Molecule Phys. Rev. Lett. [93, 18 (2004)].
The CARS Workshop at Harvard was a tremendous success. Sixteen trainees from over eight different countries attended the three day workshop. Lectures were given by CARS experts from Harvard University, Harvard Medical School, Mass General Hospital, Purdue University, Coherent, Inc, Olympus, and High Q Laser.
Science Magazine chose Single Molecule Biophysics as one of the "Runners-up Breakthrough of the Year" this December Science [302, 2041 (2003)]. The magazine published two Xie Group papers in 2003: Protein Conformational Dynamics Probed by Single-molecule Electron Transfer Science [302, 262 (2003)], and Single-Molecule Kinetics of Exonuclease Reveal Base Dependence and Dynamic Disorder Science [301, 1235 (2003)].
A feature article in J. Phys. Chem. [108, 827 (2004)] by Ji-xin Cheng and Sunney Xie provided a comprehensive review of CARS microscopy and its applications.
Recent work by David Weitz's group in the Harvard Physics Department utilized CARS microscopy as a tool to study flow and fracture in drying nanoparticle suspension Phys. Rev. Lett. [91, 224501 (2003)] and spontaneous formation of lipid structures at oil/water/lipid interfaces Langmuir [19, 10281 (2003)].
A paper by Xiaolin Nan et al. appeared in J. Lipid Res. [44, 2202 (2003)] demonstrating an interesting biomedical application of CARS microscopy to the study of the morphology of lipid droplets in live fibroblast cells, a development which may aid in the investigation of obesity.
A long-awaited paper by the Xie group in collaboration with the Xun group at Washington State University and the Cova group at Politecnico di Milano has appeared in Science [302, 262 (2003)]. Former postdoc Haw Yang and graduate student Guobin Luo have demonstrated the use of electron transfer to study conformational fluctuations of proteins, which can probe distance changes on the angstrom scale as opposed to the nanometer scale accessible by the widely used FRET technique. The observed conformational fluctuation takes place across a broad range of time scales, and is expected to be associated with the fluctuations of the enzymatic rate.
Eric Potma et al. report in J. Raman Spectrosc. [34, 642 (2003)] that CARS microscopy is able to sensitively detect a single lipid bilayer and to determine the orientation of lipid molecules.
In collaboration with the Ye group at JILA (University of Colorado, Boulder), Eric Potma et al. have developed a unique passive amplifier for picosecond pulses. Operating at a repetition rate of a few hundred kilohertz, the amplifier uses a cavity-dumped optical cavity whose length interferometrically matches that of a mode-locked Ti:sapphire laser. Optics Lett. [28, 1835 (2003)]
The Xie group, in collaboration with the Ellenberger and Richardson groups at Harvard Medical School, published a paper in Science entitled "Single-Molecule Kinetics of l Exonuclease Reveal Base Dependence and Dynamic Disorder" Science [301, 1235 (2003)]. In this work, Dr. Antoine van Oijen and Paul Blainey discuss the development of an easy and multiplexed assay for single-molecule study of nucleic acid enzymes. They observed that the rate of digestion of DNA by exonuclease is DNA sequence dependent, and fluctuates on a broad range of time scales.
The ordering of water molecules at phospholipid bilayers are directly visualized for the first time by Dr. Ji-Xin Cheng in collaboration with David Weitz's group. This nice example of the applications of CARS microscopy appears in Proc. Natl. Aca. Sci. [100, 9826 (2003).