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December 15, 2020 Webinar Speakers

Our final JAWSChem Webinar of the year 2020 will take place via the internet on Tuesday December 15th at 8pm EST/1am GMT (Dec. 16). Sign up on our mailing list to receive the zoom link!

Many thanks to those who volunteered their time, presented, moderated, attended, and watched the recording this year. You have made JAWSChem successful! We will resume our regularly scheduled programming after the new year with our first webinar taking place on January 12th, 2021 at 11am EST/4pm GMT. For now please learn more about our speakers and their research below!

Our featured speakers this week are Laura Muehlbauer (graduate student; UW-Madison, USA), Alexandra Brumberg (graduate student; Northwestern University, USA), and Dr. Saurja DasGupta (postdoctoral researcher; Massachusetts General Hospital, USA). The seminar will be guest moderated by Professor Maria Gallardo-Williams from NC State!



Biography: Laura Muehlbauer is an Analytical Chemistry PhD student at the University of Wisconsin-Madison. Laura earned her undergraduate degree in Chemistry from St. Olaf College in Northfield, MN in May 2017, graduating summa cum laude and Phi Beta Kappa. At St. Olaf, she became interested in the power of mass spectrometry to solve complex biomedical problems. Her graduate research focuses on applying mass spectrometry-based proteomics to answer different biological questions. After earning her PhD, Laura hopes to enter the intellectual property/patenting field.

Title of Talk: Global Phosphoproteome Analysis Using FAIMS on a Hybrid Orbitrap Mass Spectrometer

Abstract: Mass spectrometry is the premier tool for identifying and quantifying protein phosphorylation on a global scale. Analysis of phosphopeptides requires enrichment, and even after the samples remain highly complex and exhibit broad dynamic range of abundance. Achieving maximal depth of coverage for phosphoproteomics therefore typically necessitates offline liquid chromatography prefractionation, a time-consuming and laborious approach. Here, we incorporate a recently commercialized aerodynamic high-field asymmetric waveform ion mobility spectrometry (FAIMS) device into the phosphoproteomic workflow. We characterize the effects of phosphorylation on the FAIMS separation, describe optimized compensation voltage settings for unlabeled phosphopeptides, and demonstrate the advantages of FAIMS-enabled gas-phase fractionation. Standard FAIMS single-shot analyses identified around 15-20% additional phosphorylation sites than control experiments without FAIMS. In comparison to liquid chromatography prefractionation, FAIMS experiments yielded similar or superior results when analyzing up to four discrete gas-phase fractions. Although using FAIMS led to a modest reduction in the precision of quantitative measurements when using label-free approaches, data collected with FAIMS yielded a 26% increase in total reproducible measurements. Overall, we conclude that the new FAIMS technology is a valuable addition to any phosphoproteomic workflow, with greater benefits emerging from longer analyses and higher amounts of material.

ALEXANDRA BRUMBERG (on twitter @nanobrumberg)

Biography: Alexandra Brumberg is an NSF graduate research fellow and 5th year Ph.D. candidate in the chemistry department at Northwestern University. Her research uses ultrafast spectroscopy and other advanced characterization techniques to probe the photophysical properties of colloidal nanomaterials. Alexandra received her BS in chemistry and mathematics from Tufts University in 2016. In her spare time, Alexandra loves to read, crochet, and solve jigsaw puzzles, and is very active with the nonprofit organization Letters to a Pre-Scientist. Alexandra has never seen Jaws, but admits it may be about time.

Title of Talk: In-Plane Exciton Extent and its Effect on Electronic Interactions in 2D Semiconductor Nanoplatelets

Abstract: Recent progress in the field of nanomaterials has enabled significant advances in optoelectronic devices, such as solar cells, light-emitting diodes, photocatalysts, and sensors. These advances have been enabled by the superior optical and electronic properties of nanoparticles, which arise from quantum confinement and therefore cannot be attained using bulk materials. However, further developments in the field of nanotechnology require increased knowledge regarding how to improve nanoparticle properties.

Because nanoparticles are quantum confined, methods of altering nanoparticle properties extend beyond just changes of material composition to also those of nanoparticle size and shape. The modification of shape is especially useful when it involves changing the number of nanoscale dimensions, as quantum confinement in one, two, or three dimensions results in drastically different optical and electronic properties. However, because the electronic behavior of one- and two-dimensional nanomaterials is not captured by either that of nanoparticles confined in all three dimensions (i.e. zero-dimensional nanomaterials), nor by that of bulk materials, experimental investigations into their photophysical behaviors are needed to gain fundamental understanding regarding how nanoparticle dimensionality affects optoelectronic behavior.

In this talk, I will present my work investigating the effect of nanoparticle dimensionality on the optoelectronic behavior of semiconductor nanoplatelets (NPLs)—colloidal, two-dimensional nanoparticles that are quantum confined in only one dimension. First, I will discuss a magneto-optical study in which the lateral spatial extent of the excited electron-hole pair, or “exciton”, is determined. Exciton spatial extent dictates the strength of electronic interactions between NPLs and other materials and is often assumed to be spatially extended throughout the plane of 2D materials. However, we show that the exciton in CdSe NPLs is relatively spherical in shape, suggesting that quantum confinement in only one dimension can still have an effect on the electronic behavior in all three dimensions.

I will then discuss our group’s recent studies on the types of electronic interactions that are affected by exciton spatial extent. Interestingly, the effect of nanoparticle dimensionality on electron transfer is found to differ depending on whether the electron acceptor is a molecule or a nanoparticle. Using time-resolved photoluminescence spectroscopy, we find that electron transfer from CdSe NPLs to methylviologen is found to scale inversely with particle area, such that spherical CdSe quantum dots exhibit the fastest rate of electron transfer. However, electron transfer between CdSe and CsPbBr3 nanoparticles is found to proceed more quickly when NPLs are used in the place of quantum dots. Together, these studies delve into electronic properties that bear relevance to optoelectronic devices, showing that nanoparticle dimensionality is an important factor to consider for nanotechnology.

DR. SAURJA DASGUPTA (on twitter @SaurjaDasGupta)

Biography: Saurja DasGupta is originally from Kolkata, India. He obtained his Ph.D. at the University of Chicago, where he studied the structure, function, and evolution of catalytic RNA under the supervision of Dr. Joseph Piccirilli. He is currently a postdoctoral researcher in Dr. Jack Szostak’s group at Massachusetts General Hospital, Boston, where he is trying to understand the biochemical milieu that could have given birth to life on earth (and elsewhere). One of his scientific dreams is to observe the spontaneous emergence of Darwinian evolution in a chemical system.

Title of Talk: Chemistry and Catalysis join forces in prebiotic RNA ligation

Abstract: The ability of RNA to function as the carrier of heritable information as well as enzymes (ribozymes) have made it central to the emergence of life on earth. Modern biology uses protein polymerases to assemble RNA building blocks that are activated by triphosphate groups (NTPs); however, these building blocks are not sufficiently reactive for non-enzymatic RNA assembly. Non-enzymatic polymerization/ligation of monomers/oligomers activated by intrinsically reactive moieties like prebiotically-relevant 2-aminoimidazoles (2AI) can generate short RNA sequences, but these processes are inefficient. The appearance of ribozymes that catalyze RNA assembly was therefore a vital transition in the chemical evolution of life. The evolutionary connection between chemical assembly of reactive, prebiotic building blocks and the enzymatic assembly of building blocks activated with triphosphates would be provided by ribozymes that catalyze RNA assembly using prebiotic 2AI-activated substrates. We used in vitro selection to identify ligase ribozymes that utilize 2AI-activated RNA as substrates. Ligation was found to be dependent on a specific sequence at the 3' end of the substrate, which made ligation of shorter substrates inefficient. We rebooted selection to identify sequences that catalyze the ligation of RNA oligomers that lack the specific 3' sequence. After 10 rounds, we have identified RNA pools that join RNA pieces as short as 4 nt. These sequences will provide starting points for in vitro evolution to select polymerase ribozymes that use 2AI-activated monomers as substrates. We have also identified ligase ribozymes that function at sub-millimolar concentrations of Mg2+. The low Mg2+ requirement enabled us to constitute RNA-catalyzed RNA ligation inside prebiotic compartments made of fatty acids, as these vesicles are unstable at higher concentrations of Mg2+. This has brought us one step closer to assembling a self-replicating chemical system, capable of exhibiting Darwinian evolution.

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