acs boston update 3: thursday

August 23, 2007 at 1:18 pm | | conferences, science community, seminars

Thursday was the last day of ACS Boston. I’m tired of trying to be entertaining (you probably can’t tell the difference), so I’m just going to summarize the talks I liked:

  • Peter Lu has recently moved from PNNL to Bowling Green State University in Ohio. He talked about his fancy instrumentation that combines AFM/STM with a fluorescence/Raman microscope (with photon time-stamping and pulsed excitation, etc.).
    • First, he talked about looking at membrane-roughness changes with changes in membrane proteins: interfacial electron transfer caused changes measured by AFM and Raman.
    • Then he talked about studying LH1-LH2 FRET to probe dynamics of light-harvesting protein energy transfer. The FRET signal was rapidly fluctuating and looked like noise (not like TJ Ha’s obviously anticorrelated SM FRET time traces, for instance). Any FRET information was further obscured by Levy-flight dynamics. To glean anything from this data, he developed an analysis he called 2D cross-correlation amplitude mapping (see the new J. Phys. Chem. C paper on this analysis). He also applied this analysis to studying SM enzymatic pyrophosphorylation reaction dynamics.
  • Norbert Scherer talked about chemical-perturbation spectroscopy: watching FRET fluctuations and how they are related to periodic [Mg] jumps to probe the enzymatic reaction landscape. His experimental system is RNase P RNA labeled with Cy3/Cy5. My favorite part was when called a complicated figure on one of his slides a “ridiculogram.”
  • Jamie Boyce is a grad student finishing up in Sergei Sheiko’s lab, where I did my undergrad research. I went to her talk in the POLY division, and it was nice to see Jamie again and get an update on the lab’s work. She talked about a range of AFM studies of the shape, deformation, physics, and conformational changes of polymers with complex architectures, especially molecular “bottle brushes.”
  • Hu Cang is a postdoc in Haw Yang’s lab. They are using a scanning stage and careful setup of the confocal pinhole and detectors to track/”trap” diffusing particles in three dimensions. To get motion in the z direction, the confocal pinhole is positions slightly off the focus, so position changes are seen as intensity changes. Changes in x and y are measured using a prism mirror placed at the focus, splitting the beam to two detectors; position changes are seen as more light going to one detector. The particle (GNP, QD, fluorescent bead, etc.) is tracked by keeping it in the focus using a feedback loop with the translation stage. For a bead, they can track something with 60-nm precision in 3D. They can also learn information about rotation and shape from a dichroic beamsplitter and two detectors: the decay of the correlation reveals information about rotational dynamics. This was demonstrated by using Ag nanorods in glycerol: we were able to see correlated fluctuations. He mentioned their J. Phys. Chem. C paper on the tracking method. Here’s their J. Phys. Chem B paper about a unbiased binning method for change-point detection.
  • Peter Kapusta from PicoQuant talked about commercial implementation of Enderlein’s concept (see this ChemPhysChem paper) of using two foci to quantitatively measure the confocal spot volume for FCS.
  • Adam Cohen is a former member of the Moerner lab; he just joined the faculty at Harvard. He talked about his ABEL trap, which traps single fluorescent particles/molecules using a feedback voltage applied to the solution (pushing the dot back to the target position). He talked about his early experiments, such as DNA fluctuation dynamics. Then he talked about his “hardware trap” version, which can apply a trapping voltage with each photon measured by an APD, the trapping speed limited only by photon shot noise. He also talked about measuring dynamics of individual GroEL chaperonin molecules trapped by his machine. Finally, he talked about trying to trap single Cy3 molecules in solution. All his stuff was really impressive, but I don’t want too sound biased. (He also advertised spots in his new lab for “bright, motivated” grad students interested in building and testing novel devices.)
  • Michael Greene at NIST described some cool nanodroplets of sample in perfluorinated liquids. He could trap the nanodroplets, analyze the sample, and even bring two different droplets together. I wish I had more to say, but my brain is dead.

OK, that’s all on my reporting from ACS. Now I’ll get back to blogging about silly things…

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