March 1, 2020
by Carol Lynn Alpert
Participating: Jessica, Peter, Abhijit, Elizabeth, Thomas, Carol Lynn
News: Abhilasha has a new position at Intel Corporation in Oregon as a TD Module Etch Engineer. Abhijit interviewed at Georgia Tech for a post-doc position.
Report: Optics Team – Georgia
Peter and Abhijit recently published in Optics Letters their report on single-molecule localization using self-interference digital holography (SIDH). [see https://doi.org/10.1364/OL.379047 and https://doi.org/10.1117/12.2543422.] Using 40 and 100 nm fluorescent nanospheres, they were able to demonstrate 5 nm resolution in the lateral X-Y dimensions and 40 nm in the axial Z dimension, even with low photons detection counts. This made them curious about what the practical limits might be for single-molecule localization using SIDH, so they ran a bunch of theoretical calculations detailed in Abhijit’s post this month. The preliminary results indicate that they should be able to improve the z-dimension resolution by a factor of four, which is very encouraging.
Abhijit also includes in his post a remarkable demonstration of the increased resolution achieved through application of the new light-sheet imaging set-up. It dramatically decreases the stray light problem. They will work further on increasing photon signal by improving the optical path from objective to sample.
Report: QDot Team – Ohio
Elizabeth is still trouble-shooting the non-specific binding of DNA cages that should attach to the secondary antibodies only. She tried increasing DNA cage availability by a factor of 200, and concluded that overshot the mark. She had better success working with primary antibodies, but this is not practical for scale-up, so she will go back to focusing on refining the parameters to achieve secondary antibody binding only. Her next experiment is designed to determine the ideal amount of blocking buffer time.
Undergraduate research student Thomas Porter has been exploring storage conditions for the QD-DNA conjugates made from single-strand DNA with phytochelatin-3 (PC3) coating via copper-free click chemistry. He has been observing a decrease in fluorescence from the conjugated QDs as the batches sit in storage, awaiting use in his photo-switching experiments with gold nanoparticles (AuNPs). He'd like to maintain consistency in the baseline quantum yield of the QDs so he can more accurately measure the energy transfer between the QDs and the AuNPs that is necessary for QD quenching to occur. Theorizing oxidation as the cause of the decrease in QD fluorescence while in storage, Thomas tested two alternative storage conditions using argon gas. His results show that a continuous flow of argon in the storage container works best for maintaining consistent QD fluorescence over time. "In other words," he says, "I should be able to get better quenching in future experiments." Read more about Elizabeth's and Thomas' work here.
Report: Communications Team – Boston
Because QSTORM is not yet ready for primetime, Carol Lynn is working with Lawrence Klein Productions to produce a short film on an another instrument development project for biological research: the quest to develop automated systems that can produce a complete neuron-by-neuron digital nanoscale “connectome,” a 3D wiring diagram for the brain. This month we visited the HHMI Research center at Janelia Farms in Virginia, which, in partnership with Google Brain, has just published a fly semi-connectome. Carol Lynn was in Seattle for AAAS and while there visited the Allen Institute for Brain Science to learn more about their efforts on the mouse connectome – in partnership with the Seung Lab at Princeton - and their interest in deciphering the neural circuitry of the mouse visual cortex.
Our next QSTORM-AO phone meeting will be April 1 at 1:30. No fooling.