acs boston update 2.5: posters

August 23, 2007 at 12:53 pm | | conferences, science community, seminars

I saw many cool posters at the PHYS poster session Wednesday evening. Here are my favorite:

  • Charles Schroeder did his graduate work with Steve Chu and he’s finishing his postdoc with Sunney Xie; I did a summer REU with Chuck when he was at Stanford. For his work in the Xie lab, he used a custom promotor to incorporate fluorescein UTPs and anti-fluorescein QDs to study RNA and DNA polymerases. Looking at a DNAP/RNAP system on a chain extended from a magnetic bead using flow, he was able to track changes in position of the polymerases and chain length (using a similar technique to what Antoine van Oijen did—I summarized his stuff before). His conclusion was that DNAP moves past the position of RNAP (either over it or pushes it along the chain).
  • Stirling Churchman is just finishing up in the Spudich lab. In a collaboration with Henrik Flyvbjerg, a theorist, she has used a better fitting method than Gaussians to fit the PSF for high-precision localization. Instead of Gaussians, they use the theoretical emission pattern of a dipole emitter (taking into account the NA of the objective and the higher rate of emission into the medium with higher index of refraction) to fit the PSF. With this more accurate fitting—and a MLE algorithm—they were able to get the same localization precision using only half the photons! They’re writing up a paper now.
  • Volkan Ediz is a grad student in David Yaron’s lab. He uses QM calculations to predict some photophysical properties of a class of asymmetric cyanine dye, predicting barriers to twisting into dark states (see their JACS paper here). Their work is related to some of the work I’ve done and a previous grad student in the Moerner lab did with a different fluorophore; but their calculations are more hard-core. I met Volkan and David last year at ACS San Francisco; they’re really nice!
  • Klaus Schaper is at Heinrich-Heine-University Dusseldorf and has been synthesizing rhodamine dyes with triplet quenchers covalently attached. The concept is that the quencher will make the dye brighter by both reducing the triplet lifetime and reducing the probability of photobleaching (from excitation from triplet states or from reactive oxygen produced by interactions with the dye triplet state). He used azobenzene on a sulforhodamine B, and found that he could get at 2.5-fold increase in the maximum emission rate (before saturation and bleaching) in an FCS experiment!
  • Franziska Luschtinetz, from the University of Potsam, looked at the changes in the photophysics of biotinilated dyes (called DY-635B and DY-647B) upon binding to streptavadin. She found different effects on the absorption and fluorescence emission spectra, ranging from dye rigidization and H-type excimer behavior, upon the binding. Finally, she also did some time-dependent fluorescence anisotropy and FCS measurements with these dyes. I didn’t actually get to talk to Franziska, but she helpfully provided printouts of her poster!

One more day of ACS coming up!

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